Commit Graph

98601 Commits

Author SHA1 Message Date
Igor Mammedov
3c99559269 tests: acpi: update expected blobs
Expected change:
  -                Name (_SUN, 0x0X)  // _SUN: Slot User Number
                   Name (_ADR, 0xY)  // _ADR: Address
  ...
  +                Name (_SUN, 0xX)  // _SUN: Slot User Number

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20220701133515.137890-14-imammedo@redhat.com>
2022-10-09 16:38:46 -04:00
Igor Mammedov
366047d625 x86: pci: acpi: reorder Device's _ADR and _SUN fields
no functional change, align order of fields in empty slot
descriptor with a populated slot ordering.
Expected diff:
  -                Name (_SUN, 0x0X)  // _SUN: Slot User Number
                   Name (_ADR, 0xY)  // _ADR: Address
  ...
  +                Name (_SUN, 0xX)  // _SUN: Slot User Number

that will eliminate contextual changes (causing test failures)
when follow up patches merge code generating populated and empty
slots descriptors.

Put mandatory _ADR as the 1st field, then ASUN as it can be
present for both pupulated and empty slots and only then _SUN
which is present only when slot is hotpluggable.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20220701133515.137890-13-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-09 16:38:45 -04:00
Igor Mammedov
5d08517fd7 tests: acpi: whitelist pc/q35 DSDT before moving _ADR field
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20220701133515.137890-12-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-09 16:38:45 -04:00
Igor Mammedov
0176649070 tests: acpi: update expected blobs
It's expected that hotpluggable slots will, get ASUN variable
and use that instead of _SUN with its _DSM method.

For example:

  @@ -979,8 +979,9 @@ DefinitionBlock ("", "DSDT", 1, "BOCHS ", "BXPC    ", 0x00000001)

               Device (S18)
               {
  -                Name (_SUN, 0x03)  // _SUN: Slot User Number
  +                Name (ASUN, 0x03)
                   Name (_ADR, 0x00030000)  // _ADR: Address
  +                Name (_SUN, 0x03)  // _SUN: Slot User Number
                   Method (_EJ0, 1, NotSerialized)  // _EJx: Eject Device
                   {
                       PCEJ (BSEL, _SUN)
  @@ -991,7 +992,7 @@ DefinitionBlock ("", "DSDT", 1, "BOCHS ", "BXPC    ", 0x00000001)
                       Local0 = Package (0x02)
                           {
                               BSEL,
  -                            _SUN
  +                            ASUN
                           }
                       Return (PDSM (Arg0, Arg1, Arg2, Arg3, Local0))
                   }

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20220701133515.137890-11-imammedo@redhat.com>
2022-10-09 16:38:45 -04:00
Igor Mammedov
5840a16364 x86: acpi: cleanup PCI device _DSM duplication
add ASUN variable to hotpluggable slots and use it
instead of _SUN which has the same value to reuse
_DMS code on both branches (hot- and non-hotpluggable).
No functional change.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20220701133515.137890-10-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-09 16:38:45 -04:00
Igor Mammedov
18a31b8d3e tests: acpi: whitelist pc/q35 DSDT before switching _DSM to use ASUN
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20220701133515.137890-9-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-09 16:38:45 -04:00
Igor Mammedov
13508ea26a tests: acpi: update expected blobs
An intermediate blobs update to keep changes (last 2 patches)
reviewable.

Includes refactored PDSM that uses Package argument for custom
parameters.

 ===== PDSM taking package as arguments

             Return (Local0)
         }

-        Method (PDSM, 6, Serialized)
+        Method (PDSM, 5, Serialized)
         {
-            If ((Arg0 == ToUUID ("e5c937d0-3553-4d7a-9117-ea4d19c3434d") /* Device Labeling Interface */))
+            If ((Arg2 == Zero))
             {
-                Local0 = AIDX (Arg4, Arg5)
-                If ((Arg2 == Zero))
-                {
-                    If ((Arg1 == 0x02))
+                Local0 = Buffer (One)
                     {
-                        If (!((Local0 == Zero) | (Local0 == 0xFFFFFFFF)))
-                        {
-                            Return (Buffer (One)
-                            {
-                                 0x81                                             // .
-                            })
-                        }
+                         0x00                                             // .
                     }
+                Local1 = Zero
+                If ((Arg0 != ToUUID ("e5c937d0-3553-4d7a-9117-ea4d19c3434d") /* Device Labeling Interface */))
+                {
+                    Return (Local0)
+                }

-                    Return (Buffer (One)
-                    {
-                         0x00                                             // .
-                    })
+                If ((Arg1 < 0x02))
+                {
+                    Return (Local0)
                 }
-                ElseIf ((Arg2 == 0x07))
+
+                Local2 = AIDX (DerefOf (Arg4 [Zero]), DerefOf (Arg4 [One]
+                    ))
+                If (!((Local2 == Zero) | (Local2 == 0xFFFFFFFF)))
                 {
-                    Local1 = Package (0x02)
-                        {
-                            Zero,
-                            ""
-                        }
-                    Local1 [Zero] = Local0
-                    Return (Local1)
+                    Local1 |= One
+                    Local1 |= (One << 0x07)
                 }
+
+                Local0 [Zero] = Local1
+                Return (Local0)
+            }
+
+            If ((Arg2 == 0x07))
+            {
+                Local0 = Package (0x02)
+                    {
+                        Zero,
+                        ""
+                    }
+                Local2 = AIDX (DerefOf (Arg4 [Zero]), DerefOf (Arg4 [One]
+                    ))
+                Local0 [Zero] = Local2
+                Return (Local0)
             }
         }
     }

 =====  PCI slot using Package to pass arguments to _DSM

                 Name (ASUN, Zero)
                 Method (_DSM, 4, Serialized)  // _DSM: Device-Specific Method
                 {
-                    Return (PDSM (Arg0, Arg1, Arg2, Arg3, BSEL, ASUN))
+                    Local0 = Package (0x02)
+                        {
+                            BSEL,
+                            ASUN
+                        }
+                    Return (PDSM (Arg0, Arg1, Arg2, Arg3, Local0))
                 }
             }

 ===== hotpluggable PCI slot using Package to pass arguments to _DSM

                 Method (_DSM, 4, Serialized)  // _DSM: Device-Specific Method
                 {
-                    Return (PDSM (Arg0, Arg1, Arg2, Arg3, BSEL, _SUN))
+                    Local0 = Package (0x02)
+                        {
+                            BSEL,
+                            _SUN
+                        }
+                    Return (PDSM (Arg0, Arg1, Arg2, Arg3, Local0))
                 }
             }

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20220701133515.137890-8-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-09 16:38:45 -04:00
Igor Mammedov
467d099a29 x86: acpi: _DSM: use Package to pass parameters
Numer of possible arguments to pass to a method is limited
in ACPI. The following patches will need to pass over more
parameters to PDSM method, will hit that limit.

Prepare for this by passing structure (Package) to method,
which let us workaround arguments limitation.
Pass to PDSM all standard arguments of _DSM as is, and
pack custom parameters into Package that is passed as
the last argument to PDSM.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20220701133515.137890-7-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-09 16:38:45 -04:00
Igor Mammedov
a12cf6923c acpi: x86: refactor PDSM method to reduce nesting
.., it will help with code readability and make easier
to extend method in followup patches

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20220701133515.137890-6-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-09 16:38:45 -04:00
Igor Mammedov
31b5dd0390 tests: acpi: whitelist pc/q35 DSDT due to HPET AML move
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20220701133515.137890-5-imammedo@redhat.com>
2022-10-09 16:38:45 -04:00
Igor Mammedov
4609296d06 tests: acpi: update expected blobs after HPET move
HPET AML moved after PCI host bridge description (no functional change)

diff example for PC machine:

@@ -54,47 +54,6 @@ DefinitionBlock ("", "DSDT", 1, "BOCHS ", "BXPC    ", 0x00000001)
         }
     }

-    Scope (_SB)
-    {
-        Device (HPET)
-        {
-            Name (_HID, EisaId ("PNP0103") /* HPET System Timer */)  // _HID: Hardware ID
-            Name (_UID, Zero)  // _UID: Unique ID
-            OperationRegion (HPTM, SystemMemory, 0xFED00000, 0x0400)
-            Field (HPTM, DWordAcc, Lock, Preserve)
-            {
-                VEND,   32,
-                PRD,    32
-            }
-
-            Method (_STA, 0, NotSerialized)  // _STA: Status
-            {
-                Local0 = VEND /* \_SB_.HPET.VEND */
-                Local1 = PRD /* \_SB_.HPET.PRD_ */
-                Local0 >>= 0x10
-                If (((Local0 == Zero) || (Local0 == 0xFFFF)))
-                {
-                    Return (Zero)
-                }
-
-                If (((Local1 == Zero) || (Local1 > 0x05F5E100)))
-                {
-                    Return (Zero)
-                }
-
-                Return (0x0F)
-            }
-
-            Name (_CRS, ResourceTemplate ()  // _CRS: Current Resource Settings
-            {
-                Memory32Fixed (ReadOnly,
-                    0xFED00000,         // Address Base
-                    0x00000400,         // Address Length
-                    )
-            })
-        }
-    }
-
     Scope (_SB.PCI0)
     {
         Device (ISA)
@@ -529,6 +488,47 @@ DefinitionBlock ("", "DSDT", 1, "BOCHS ", "BXPC    ", 0x00000001)
         }
     }

+    Scope (_SB)
+    {
+        Device (HPET)
+        {
+            Name (_HID, EisaId ("PNP0103") /* HPET System Timer */)  // _HID: Hardware ID
+            Name (_UID, Zero)  // _UID: Unique ID
+            OperationRegion (HPTM, SystemMemory, 0xFED00000, 0x0400)
+            Field (HPTM, DWordAcc, Lock, Preserve)
+            {
+                VEND,   32,
+                PRD,    32
+            }
+
+            Method (_STA, 0, NotSerialized)  // _STA: Status
+            {
+                Local0 = VEND /* \_SB_.HPET.VEND */
+                Local1 = PRD /* \_SB_.HPET.PRD_ */
+                Local0 >>= 0x10
+                If (((Local0 == Zero) || (Local0 == 0xFFFF)))
+                {
+                    Return (Zero)
+                }
+
+                If (((Local1 == Zero) || (Local1 > 0x05F5E100)))
+                {
+                    Return (Zero)
+                }
+
+                Return (0x0F)
+            }
+
+            Name (_CRS, ResourceTemplate ()  // _CRS: Current Resource Settings
+            {
+                Memory32Fixed (ReadOnly,
+                    0xFED00000,         // Address Base
+                    0x00000400,         // Address Length
+                    )
+            })
+        }
+    }
+
     Scope (_SB)
     {
         Device (\_SB.PCI0.PRES)

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20220701133515.137890-4-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-09 16:38:45 -04:00
Igor Mammedov
e05acc360e acpi: x86: deduplicate HPET AML building
HPET AML doesn't depend on piix4 nor q35, move code buiding it
to common scope to avoid duplication.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20220701133515.137890-3-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-09 16:38:45 -04:00
Igor Mammedov
beec628c80 tests: acpi: whitelist pc/q35 DSDT due to HPET AML move
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20220701133515.137890-2-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-09 16:38:45 -04:00
Hal Martin
fd8caa253c hw/smbios: support for type 8 (port connector)
PATCH v1: add support for SMBIOS type 8 to qemu
PATCH v2: incorporate patch v1 feedback and add smbios type=8 to qemu-options

internal_reference: internal reference designator
external_reference: external reference designator
connector_type: hex value for port connector type (see SMBIOS 7.9.2)
port_type: hex value for port type (see SMBIOS 7.9.3)

After studying various vendor implementationsi (Dell, Lenovo, MSI),
the value of internal connector type was hard-coded to 0x0 (None).

Example usage:
-smbios type=8,internal_reference=JUSB1,external_reference=USB1,connector_type=0x12,port_type=0x10 \
-smbios type=8,internal_reference=JAUD1,external_reference="Audio Jack",connector_type=0x1f,port_type=0x1d \
-smbios type=8,internal_reference=LAN,external_reference=Ethernet,connector_type=0x0b,port_type=0x1f \
-smbios type=8,internal_reference=PS2,external_reference=Mouse,connector_type=0x0f,port_type=0x0e \
-smbios type=8,internal_reference=PS2,external_reference=Keyboard,connector_type=0x0f,port_type=0x0d

Signed-off-by: Hal Martin <hal.martin@gmail.com>

Message-Id: <20220812135153.17859-1-hal.martin@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-09 16:38:45 -04:00
Peter Maydell
775cc426a9 pci: Sanity check mask argument to pci_set_*_by_mask()
Coverity complains that in functions like pci_set_word_by_mask()
we might end up shifting by more than 31 bits. This is true,
but only if the caller passes in a zero mask. Help Coverity out
by asserting that the mask argument is valid.

Fixes: CID 1487168

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20220818135421.2515257-3-peter.maydell@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
2022-10-09 16:38:45 -04:00
Peter Maydell
31e039e76d pci: Remove unused pci_get_*_by_mask() functions
The helper functions pci_get_{byte,word,long,quad}_by_mask()
were added in 2012 in commit c9f50cea70. In the decade
since we have never added a single use of them.

The helpers clearly aren't that helpful, so drop them
rather than carrying around dead code.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20220818135421.2515257-2-peter.maydell@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
2022-10-09 16:38:45 -04:00
Laurent Vivier
8a8287981d hmp: add virtio commands
This patch implements the HMP versions of the virtio QMP commands.

[Jonah: Adjusted hmp monitor output format for features / statuses
	with their descriptions.]

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
Message-Id: <1660220684-24909-7-git-send-email-jonah.palmer@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-09 16:38:45 -04:00
Laurent Vivier
1ee7bb5bef qmp: add QMP command x-query-virtio-queue-element
This new command shows the information of a VirtQueue element.

[Note: Up until v10 of this patch series, virtio.json had many (15+)
 enums defined (e.g. decoded device features, statuses, etc.). In v10
 most of these enums were removed and replaced with string literals.
 By doing this we get (1) simpler schema, (2) smaller generated code,
 and (3) less maintenance burden for when new things are added (e.g.
 devices, device features, etc.).]

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
Message-Id: <1660220684-24909-6-git-send-email-jonah.palmer@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-09 16:38:45 -04:00
Laurent Vivier
07536ddda7 qmp: add QMP commands for virtio/vhost queue-status
These new commands show the internal status of a VirtIODevice's
VirtQueue and a vhost device's vhost_virtqueue (if active).

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
Message-Id: <1660220684-24909-5-git-send-email-jonah.palmer@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-09 16:38:45 -04:00
Laurent Vivier
f3034ad71f qmp: decode feature & status bits in virtio-status
Display feature names instead of bitmaps for host, guest, and
backend for VirtIODevices.

Display status names instead of bitmaps for VirtIODevices.

Display feature names instead of bitmaps for backend, protocol,
acked, and features (hdev->features) for vhost devices.

Decode features according to device ID. Decode statuses
according to configuration status bitmap (config_status_map).
Decode vhost user protocol features according to vhost user
protocol bitmap (vhost_user_protocol_map).

Transport features are on the first line. Undecoded bits (if
any) are stored in a separate field.

[Jonah: Several changes made to this patch from prev. version (v14):
 - Moved all device features mappings to hw/virtio/virtio.c
 - Renamed device features mappings (less generic)
 - Generalized @FEATURE_ENTRY macro for all device mappings
 - Virtio device feature map definitions include descriptions of
   feature bits
 - Moved @VHOST_USER_F_PROTOCOL_FEATURES feature bit from transport
   feature map to vhost-user-supported device feature mappings
   (blk, fs, i2c, rng, net, gpu, input, scsi, vsock)
 - New feature bit added for virtio-vsock: @VIRTIO_VSOCK_F_SEQPACKET
 - New feature bit added for virtio-iommu: @VIRTIO_IOMMU_F_BYPASS_CONFIG
 - New feature bit added for virtio-mem: @VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE
 - New virtio transport feature bit added: @VIRTIO_F_IN_ORDER
 - Added device feature map definition for virtio-rng
]

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
Message-Id: <1660220684-24909-4-git-send-email-jonah.palmer@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-09 16:38:45 -04:00
Laurent Vivier
90c066cd68 qmp: add QMP command x-query-virtio-status
This new command shows the status of a VirtIODevice, including
its corresponding vhost device's status (if active).

Next patch will improve output by decoding feature bits, including
vhost device's feature bits (backend, protocol, acked, and features).
Also will decode status bits of a VirtIODevice.

[Jonah: From patch v12; added a check to @virtio_device_find to ensure
 synchronicity between @virtio_list and the devices in the QOM
 composition tree.]

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
Message-Id: <1660220684-24909-3-git-send-email-jonah.palmer@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-09 16:38:45 -04:00
Laurent Vivier
a5ebce3857 qmp: add QMP command x-query-virtio
This new command lists all the instances of VirtIODevices with
their canonical QOM path and name.

[Jonah: @virtio_list duplicates information that already exists in
 the QOM composition tree. However, extracting necessary information
 from this tree seems to be a bit convoluted.

 Instead, we still create our own list of realized virtio devices
 but use @qmp_qom_get with the device's canonical QOM path to confirm
 that the device exists and is realized. If the device exists but
 is actually not realized, then we remove it from our list (for
 synchronicity to the QOM composition tree).

 Also, the QMP command @x-query-virtio is redundant as @qom-list
 and @qom-get are sufficient to search '/machine/' for realized
 virtio devices. However, @x-query-virtio is much more convenient
 in listing realized virtio devices.]

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
Message-Id: <1660220684-24909-2-git-send-email-jonah.palmer@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-09 16:38:45 -04:00
Peter Xu
20ca47429e Revert "intel_iommu: Fix irqchip / X2APIC configuration checks"
It's true that when vcpus<=255 we don't require the length of 32bit APIC
IDs.  However here since we already have EIM=ON it means the hypervisor
will declare the VM as x2apic supported (e.g. VT-d ECAP register will have
EIM bit 4 set), so the guest should assume the APIC IDs are 32bits width
even if vcpus<=255.  In short, commit 77250171bd breaks any simple cmdline
that wants to boot a VM with >=9 but <=255 vcpus with:

  -device intel-iommu,intremap=on

For anyone who does not want to enable x2apic, we can use eim=off in the
intel-iommu parameters to skip enabling KVM x2apic.

This partly reverts commit 77250171bd, while
keeping the valid bit on checking split irqchip, but revert the other change.

One thing to mention is that this patch may break migration compatibility
of such VM, however that's probably the best thing we can do, because the
old behavior was simply wrong and not working for >8 vcpus.  For <=8 vcpus,
there could be a light guest ABI change (by enabling KVM x2apic after this
patch), but logically it shouldn't affect the migration from working.

Also, this is not the 1st commit to change x2apic behavior.  Igor provided
a full history of how this evolved for the past few years:

https://lore.kernel.org/qemu-devel/20220922154617.57d1a1fb@redhat.com/

Relevant commits for reference:

  fb506e701e ("intel_iommu: reject broken EIM", 2016-10-17)
  c1bb5418e3 ("target/i386: Support up to 32768 CPUs without IRQ remapping", 2020-12-10)
  77250171bd ("intel_iommu: Fix irqchip / X2APIC configuration checks", 2022-05-16)
  dc89f32d92 ("target/i386: Fix sanity check on max APIC ID / X2APIC enablement", 2022-05-16)

We may want to have this for stable too (mostly for 7.1.0 only).  Adding a
fixes tag.

Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Claudio Fontana <cfontana@suse.de>
Cc: Igor Mammedov <imammedo@redhat.com>
Fixes: 77250171bd ("intel_iommu: Fix irqchip / X2APIC configuration checks")
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20220926153206.10881-1-peterx@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
2022-10-09 16:38:45 -04:00
Jonathan Cameron
9c769e0446 mem/cxl-type3: Add sn option to provide serial number for PCI ecap
The Device Serial Number Extended Capability PCI r6.0 sec 7.9.3
provides a standard way to provide a device serial number as
an IEEE defined 64-bit extended unique identifier EUI-64.

CXL 2.0 section 8.1.12.2 Memory Device PCIe Capabilities and
Extended Capabilities requires this to be used to uniquely
identify CXL memory devices.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20220923161835.9805-1-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Ben Widawsky <bwidawsk@kernel.org>
2022-10-09 16:38:45 -04:00
Miguel Luis
0a17270761 tests/acpi: virt: update ACPI GTDT binaries
Step 6 & 7 of the bios-tables-test.c documented procedure.

Differences between disassembled ASL files for GTDT:

    @@ -13,14 +13,14 @@
     [000h 0000   4]                    Signature : "GTDT"    [Generic Timer Description Table]
     [004h 0004   4]                 Table Length : 00000060
     [008h 0008   1]                     Revision : 02
    -[009h 0009   1]                     Checksum : 8C
    +[009h 0009   1]                     Checksum : 9C
     [00Ah 0010   6]                       Oem ID : "BOCHS "
     [010h 0016   8]                 Oem Table ID : "BXPC    "
     [018h 0024   4]                 Oem Revision : 00000001
     [01Ch 0028   4]              Asl Compiler ID : "BXPC"
     [020h 0032   4]        Asl Compiler Revision : 00000001

    -[024h 0036   8]        Counter Block Address : 0000000000000000
    +[024h 0036   8]        Counter Block Address : FFFFFFFFFFFFFFFF
     [02Ch 0044   4]                     Reserved : 00000000

     [030h 0048   4]         Secure EL1 Interrupt : 0000001D
    @@ -46,16 +46,16 @@
                                     Trigger Mode : 0
                                         Polarity : 0
                                        Always On : 0
    -[050h 0080   8]   Counter Read Block Address : 0000000000000000
    +[050h 0080   8]   Counter Read Block Address : FFFFFFFFFFFFFFFF

     [058h 0088   4]         Platform Timer Count : 00000000
     [05Ch 0092   4]        Platform Timer Offset : 00000000

     Raw Table Data: Length 96 (0x60)

    -    0000: 47 54 44 54 60 00 00 00 02 8C 42 4F 43 48 53 20  // GTDT`.....BOCHS
    +    0000: 47 54 44 54 60 00 00 00 02 9C 42 4F 43 48 53 20  // GTDT`.....BOCHS
         0010: 42 58 50 43 20 20 20 20 01 00 00 00 42 58 50 43  // BXPC    ....BXPC
    -    0020: 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  // ................
    +    0020: 01 00 00 00 FF FF FF FF FF FF FF FF 00 00 00 00  // ................
         0030: 1D 00 00 00 00 00 00 00 1E 00 00 00 04 00 00 00  // ................
         0040: 1B 00 00 00 00 00 00 00 1A 00 00 00 00 00 00 00  // ................
    -    0050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  // ................
    +    0050: FF FF FF FF FF FF FF FF 00 00 00 00 00 00 00 00  // ................

Signed-off-by: Miguel Luis <miguel.luis@oracle.com>
Message-Id: <20220920162137.75239-4-miguel.luis@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Ani Sinha <ani@anisinha.ca>
2022-10-09 16:38:45 -04:00
Miguel Luis
5dbc9a2785 acpi: arm/virt: build_gtdt: fix invalid 64-bit physical addresses
Per the ACPI 6.5 specification, on the GTDT Table Structure, the Counter Control
Block Address and Counter Read Block Address fields of the GTDT table should be
set to 0xFFFFFFFFFFFFFFFF if not provided, rather than 0x0.

Fixes: 41041e5708 ("acpi: arm/virt: build_gtdt: use acpi_table_begin()/acpi_table_end() instead of build_header()")

Signed-off-by: Miguel Luis <miguel.luis@oracle.com>
Message-Id: <20220920162137.75239-3-miguel.luis@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Ani Sinha <ani@anisinha.ca>
2022-10-09 16:38:45 -04:00
Miguel Luis
b1b146f53c tests/acpi: virt: allow acpi GTDT changes
Step 3 from bios-tables-test.c documented procedure.

Signed-off-by: Miguel Luis <miguel.luis@oracle.com>
Message-Id: <20220920162137.75239-2-miguel.luis@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Ani Sinha <ani@anisinha.ca>
2022-10-09 16:38:45 -04:00
Daniil Tatianin
8edd56735b vhost-user-blk: dynamically resize config space based on features
Make vhost-user-blk backwards compatible when migrating from older VMs
running with modern features turned off, the same way it was done for
virtio-blk in 20764be042 ("virtio-blk: set config size depending on the features enabled")

It's currently impossible to migrate from an older VM with
vhost-user-blk (with disable-legacy=off) because of errors like this:

qemu-system-x86_64: get_pci_config_device: Bad config data: i=0x10 read: 41 device: 1 cmask: ff wmask: 80 w1cmask:0
qemu-system-x86_64: Failed to load PCIDevice:config
qemu-system-x86_64: Failed to load virtio-blk:virtio
qemu-system-x86_64: error while loading state for instance 0x0 of device '0000:00:05.0:00.0:02.0/virtio-blk'
qemu-system-x86_64: load of migration failed: Invalid argument

This is caused by the newer (destination) VM requiring a bigger BAR0
alignment because it has to cover a bigger configuration space, which
isn't actually needed since those additional config fields are not
active (write-zeroes/discard).

Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Message-Id: <20220906073111.353245-6-d-tatianin@yandex-team.ru>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-07 09:41:51 -04:00
Daniil Tatianin
f1c25f295d vhost-user-blk: make 'config_wce' part of 'host_features'
No reason to have this be a separate field. This also makes it more akin
to what the virtio-blk device does.

Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Message-Id: <20220906073111.353245-5-d-tatianin@yandex-team.ru>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-07 09:41:51 -04:00
Daniil Tatianin
246db16d43 vhost-user-blk: make it possible to disable write-zeroes/discard
It is useful to have the ability to disable these features for
compatibility with older VMs that don't have these implemented.

Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Message-Id: <20220906073111.353245-4-d-tatianin@yandex-team.ru>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-07 09:41:51 -04:00
Daniil Tatianin
d9cf55a86d virtio-blk: move config size params to virtio-blk-common
This way we can reuse it for other virtio-blk devices, e.g
vhost-user-blk, which currently does not control its config space size
dynamically.

Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Message-Id: <20220906073111.353245-3-d-tatianin@yandex-team.ru>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-07 09:41:51 -04:00
Daniil Tatianin
d74c30c811 virtio: introduce VirtIOConfigSizeParams & virtio_get_config_size
This is the first step towards moving all device config size calculation
logic into the virtio core code. In particular, this adds a struct that
contains all the necessary information for common virtio code to be able
to calculate the final config size for a device. This is expected to be
used with the new virtio_get_config_size helper, which calculates the
final length based on the provided host features.

This builds on top of already existing code like VirtIOFeature and
virtio_feature_get_config_size(), but adds additional fields, as well as
sanity checking so that device-specifc code doesn't have to duplicate it.

An example usage would be:

    static const VirtIOFeature dev_features[] = {
        {.flags = 1ULL << FEATURE_1_BIT,
         .end = endof(struct virtio_dev_config, feature_1)},
        {.flags = 1ULL << FEATURE_2_BIT,
         .end = endof(struct virtio_dev_config, feature_2)},
        {}
    };

    static const VirtIOConfigSizeParams dev_cfg_size_params = {
        .min_size = DEV_BASE_CONFIG_SIZE,
        .max_size = sizeof(struct virtio_dev_config),
        .feature_sizes = dev_features
    };

    // code inside my_dev_device_realize()
    size_t config_size = virtio_get_config_size(&dev_cfg_size_params,
                                                host_features);
    virtio_init(vdev, VIRTIO_ID_MYDEV, config_size);

Currently every device is expected to write its own boilerplate from the
example above in device_realize(), however, the next step of this
transition is moving VirtIOConfigSizeParams into VirtioDeviceClass,
so that it can be done automatically by the virtio initialization code.

All of the users of virtio_feature_get_config_size have been converted
to use virtio_get_config_size so it's no longer needed and is removed
with this commit.

Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
Message-Id: <20220906073111.353245-2-d-tatianin@yandex-team.ru>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-07 09:41:51 -04:00
Alex Bennée
8fcfc8235e tests/qtest: enable tests for virtio-gpio
We don't have a virtio-gpio implementation in QEMU and only
support a vhost-user backend. The QEMU side of the code is minimal so
it should be enough to instantiate the device and pass some vhost-user
messages over the control socket. To do this we hook into the existing
vhost-user-test code and just add the bits required for gpio.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Eric Auger <eric.auger@redhat.com>
Message-Id: <20220408155704.2777166-1-alex.bennee@linaro.org>

Message-Id: <20220802095010.3330793-23-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-07 09:41:51 -04:00
Alex Bennée
19d55a19a4 tests/qtest: add a get_features op to vhost-user-test
As we expand this test for more virtio devices we will need to support
different feature sets. Add a mandatory op field to fetch the list of
features needed for the test itself.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220802095010.3330793-22-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-07 09:41:51 -04:00
Alex Bennée
ff070f602a tests/qtest: implement stub for VHOST_USER_GET_CONFIG
We don't implement the full solution because frankly none of the tests
need to at the moment. We may end up re-implementing libvhostuser in
the end.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220802095010.3330793-21-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-07 09:41:51 -04:00
Alex Bennée
3bd869f36e tests/qtest: add assert to catch bad features
No device driver (which is what the qvirtio_ access functions
represent) should be setting UNUSED(30) in the feature space. Although
existing libqos users mask it out lets ensure nothing sneaks through.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220802095010.3330793-20-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-07 09:41:51 -04:00
Alex Bennée
f48d994fb5 tests/qtest: plain g_assert for VHOST_USER_F_PROTOCOL_FEATURES
checkpatch.pl warns that non-plain asserts should be avoided so
convert the check to a plain g_assert.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220802095010.3330793-19-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-07 09:41:51 -04:00
Alex Bennée
20a4127fbd tests/qtest: catch unhandled vhost-user messages
We don't need to action every message but lets document the ones we
are expecting to consume so future tests don't get confused about
unhandled bits.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

Message-Id: <20220802095010.3330793-18-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-07 09:41:51 -04:00
Alex Bennée
30ea13e9d9 tests/qtest: use qos_printf instead of g_test_message
The vhost-user tests respawn qos-test as a standalone process. As a
result the gtester framework squashes all messages coming out of it
which make it hard to debug. As the test does not care about asserting
certain messages just convert the tests to use the direct qos_printf.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220802095010.3330793-17-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-07 09:41:51 -04:00
Alex Bennée
ebaa07083b tests/qtest: add a timeout for subprocess_run_one_test
Hangs have been observed in the tests and currently we don't timeout
if a subprocess hangs. Rectify that.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>

Message-Id: <20220802095010.3330793-16-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
2022-10-07 09:41:51 -04:00
Alex Bennée
bbd9711537 tests/qtest: pass stdout/stderr down to subtests
When trying to work out what the virtio-net-tests where doing it was
hard because the g_test_trap_subprocess redirects all output to
/dev/null. Lift this restriction by using the appropriate flags so you
can see something similar to what the vhost-user-blk tests show when
running.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20220407150042.2338562-1-alex.bennee@linaro.org>

Message-Id: <20220802095010.3330793-15-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-07 09:41:51 -04:00
Viresh Kumar
25c60a4612 hw/virtio: add vhost-user-gpio-pci boilerplate
This allows is to instantiate a vhost-user-gpio device as part of a PCI
bus. It is mostly boilerplate which looks pretty similar to the
vhost-user-fs-pci device.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <5f560cab92d0d789b1c94295ec74b9952907d69d.1641987128.git.viresh.kumar@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

Message-Id: <20220802095010.3330793-14-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-07 09:41:51 -04:00
Viresh Kumar
27ba7b027f hw/virtio: add boilerplate for vhost-user-gpio device
This creates the QEMU side of the vhost-user-gpio device which connects
to the remote daemon. It is based of vhost-user-i2c code.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <5390324a748194a21bc99b1538e19761a8c64092.1641987128.git.viresh.kumar@linaro.org>
[AJB: fixes for qtest, tweaks to feature bits]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Cc: Vincent Whitchurch <vincent.whitchurch@axis.com>

Message-Id: <20220802095010.3330793-13-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-07 09:41:51 -04:00
Alex Bennée
b8f3e6a18d hw/virtio: move vhd->started check into helper and add FIXME
The `started` field is manipulated internally within the vhost code
except for one place, vhost-user-blk via f5b22d06fb (vhost: recheck
dev state in the vhost_migration_log routine). Mark that as a FIXME
because it introduces a potential race. I think the referenced fix
should be tracking its state locally.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220802095010.3330793-12-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Raphael Norwitz <raphael.norwittz@nutanix.com>
2022-10-07 09:41:51 -04:00
Alex Bennée
9f6bcfd99f hw/virtio: move vm_running check to virtio_device_started
All the boilerplate virtio code does the same thing (or should at
least) of checking to see if the VM is running before attempting to
start VirtIO. Push the logic up to the common function to avoid
getting a copy and paste wrong.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220802095010.3330793-11-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-07 09:41:51 -04:00
Alex Bennée
a276123119 hw/virtio: add some vhost-user trace events
These are useful for tracing the lifetime of vhost-user connections.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220802095010.3330793-10-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
2022-10-07 09:41:51 -04:00
Alex Bennée
8d11c10d06 hw/virtio: log potentially buggy guest drivers
If the guest driver attempts to use the UNUSED(30) bit it is
potentially buggy as 6.3 Legacy Interface: Reserved Feature Bits
states it "SHOULD NOT be negotiated". For now just log this guest
error.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220802095010.3330793-9-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-07 09:41:51 -04:00
Alex Bennée
c97c76b3e7 hw/virtio: fix some coding style issues
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220802095010.3330793-8-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
2022-10-07 09:41:51 -04:00
Alex Bennée
c7066f2d30 include/hw: document vhost_dev feature life-cycle
Try and explicitly document the various state of feature bits as
related to the vhost_dev structure. Importantly the backend_features
can advertise things like VHOST_USER_F_PROTOCOL_FEATURES which is
never exposed to the driver and is only present in the vhost-user
feature negotiation.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220802095010.3330793-7-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
2022-10-07 09:41:51 -04:00
Alex Bennée
ea5d6ea778 include/hw/virtio: more comment for VIRTIO_F_BAD_FEATURE
When debugging a new vhost user you may be surprised to see
VHOST_USER_F_PROTOCOL getting squashed in the maze of
backend_features, acked_features and guest_features. Expand the
description here to help the next poor soul trying to work through
this.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

Message-Id: <20220802095010.3330793-6-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2022-10-07 09:41:51 -04:00