The first sunhme NIC gets placed a function 1 on slot 1 of PCI bus A,
and the rest are dynamically assigned on PCI bus B.
Previously, any PCI NIC would get the special treatment purely by
virtue of being first in the list.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Previously, the first PCI NIC would be assigned to slot 2 even if the
user override the model and made it something other than an rtl8139
which is the default. Everything else would be dynamically assigned.
Now, the first rtl8139 gets slot 2 and everything else is dynamic.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Yoshinori Sato <ysato@users.sourceforge.jp>
Avoid directly referencing nd_table[] by first instantiating any
spapr-vlan devices using a qemu_get_nic_info() loop, then calling
pci_init_nic_devices() to do the rest.
No functional change intended.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Previously, the first PCI NIC would be placed in PCI slot 3 and the rest
would be dynamically assigned. Even if the user overrode the default NIC
type and made it something other than PCNet.
Now, the first PCNet NIC (that is, anything not explicitly specified
to be anything different) will go to slot 3 even if it isn't the first
NIC specified on the command line. And anything else will be dynamically
assigned.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Thomas Huth <thuth@redhat.com>
The Malta board setup code would previously place the first NIC into PCI
slot 11 if was a PCNet card, and the rest (including the first if it was
anything other than a PCNet card) would be dynamically assigned.
Now it will place any PCNet NIC into slot 11, and then anything else will
be dynamically assigned.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Thomas Huth <thuth@redhat.com>
The previous behaviour was: *if* the first NIC specified on the command
line was an RTL8139 (or unspecified model) then it gets assigned to PCI
slot 7, which is where the Fuloong board had an RTL8139. All other
devices (including the first, if it was specified as anything other than
an rtl8319) get dynamically assigned on the bus.
The new behaviour is subtly different: If the first NIC was given a
specific model *other* than rtl8139, and a subsequent NIC was not,
then the rtl8139 (or unspecified) NIC will go to slot 7 and the rest
will be dynamically assigned.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Thomas Huth <thuth@redhat.com>
When instantiating XenBus itself, for each NIC which is configured with
either the model unspecified, or set to to "xen" or "xen-net-device",
create a corresponding xen-net-device for it.
Now we can revert the previous more hackish version which relied on the
platform code explicitly registering the NICs on its own XenBus, having
returned the BusState* from xen_bus_init() itself.
This also fixes the setup for Xen PV guests, which was previously broken
in various ways and never actually managed to peer with the netdev.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
Eliminate direct access to nd_table[] and nb_nics by processing the the
Xen and ISA NICs first and then calling pci_init_nic_devices() for the
rest.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
The loop over nd_table[] to add PCI NICs is repeated in quite a few
places. Add a helper function to do it.
Some platforms also try to instantiate a specific model in a specific
slot, to match the real hardware. Add pci_init_nic_in_slot() for that
purpose.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
This will instantiate any NICs which live on a given bus type. Each bus
is allowed *one* substitution (for PCI it's virtio → virtio-net-pci, for
Xen it's xen → xen-net-device; no point in overengineering it unless we
actually want more).
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
By noting the models for which a configuration was requested, we can give
the user an accurate list of which NIC models were actually available on
the platform/configuration that was otherwise chosen.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
Most code which directly accesses nd_table[] and nb_nics uses them for
one of two things. Either "I have created a NIC device and I'd like a
configuration for it", or "I will create a NIC device *if* there is a
configuration for it". With some variants on the theme around whether
they actually *check* if the model specified in the configuration is
the right one.
Provide functions which perform both of those, allowing platforms to
be a little more consistent and as a step towards making nd_table[]
and nb_nics private to the net code.
One might argue that platforms ought to be consistent about whether
they create the unconfigured devices or not, but making significant
user-visible changes is explicitly *not* the intent right now.
The new functions leave the 'model' field of the NICInfo as NULL after
using it for the default NIC model, unlike the qemu_check_nic_model()
function which does set nd->model to match default_model explicitly.
This is acceptable because there is no code which consumes nd->model
except this NIC-matching code in net/net.c, and no reasonable excuse
for any code wanting to use nd->model in future.
Also export the qemu_find_nic_info() helper, as some platforms have
special cases they need to handle.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
This patch will allow the SPI controller to be accessible from BCM2835 based
boards as SPI0. SPI driver is usually disabled by default and config.txt does
not work.
Instead, dtmerge can be used to apply spi=on on a bcm2835 dtb file.
Signed-off-by: Rayhan Faizel <rayhan.faizel@gmail.com>
Message-id: 20240129221807.2983148-3-rayhan.faizel@gmail.com
[PMM: indent tweak]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This patch adds the SPI controller for the BCM2835. Polling and interrupt modes
of transfer are supported. DMA and LoSSI modes are currently unimplemented.
Signed-off-by: Rayhan Faizel <rayhan.faizel@gmail.com>
Message-id: 20240129221807.2983148-2-rayhan.faizel@gmail.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
- Implementation of Transmit function for packets
- Implementation for reading and writing from and to descriptors in
memory for Tx
Added relevant trace-events
NOTE: This function implements the steps detailed in the datasheet for
transmitting messages from the GMAC.
Change-Id: Icf14f9fcc6cc7808a41acd872bca67c9832087e6
Signed-off-by: Nabih Estefan <nabihestefan@google.com>
Reviewed-by: Tyrone Ting <kfting@nuvoton.com>
Message-id: 20240131002800.989285-6-nabihestefan@google.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
- Implementation of Receive function for packets
- Implementation for reading and writing from and to descriptors in
memory for Rx
When RX starts, we need to flush the queued packets so that they
can be received by the GMAC device. Without this it won't work
with TAP NIC device.
When RX descriptor list is full, it returns a DMA_STATUS for
software to handle it. But there's no way to indicate the software has
handled all RX descriptors and the whole pipeline stalls.
We do something similar to NPCM7XX EMC to handle this case.
1. Return packet size when RX descriptor is full, effectively dropping
these packets in such a case.
2. When software clears RX descriptor full bit, continue receiving
further packets by flushing QEMU packet queue.
Added relevant trace-events
Change-Id: I132aa254a94cda1a586aba2ea33bbfc74ecdb831
Signed-off-by: Hao Wu <wuhaotsh@google.com>
Signed-off-by: Nabih Estefan <nabihestefan@google.com>
Reviewed-by: Tyrone Ting <kfting@nuvoton.com>
Message-id: 20240131002800.989285-5-nabihestefan@google.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
- Created qtest to check initialization of registers in GMAC Module.
- Implemented test into Build File.
Change-Id: I8b2fe152d3987a7eec4cf6a1d25ba92e75a5391d
Signed-off-by: Nabih Estefan <nabihestefan@google.com>
Reviewed-by: Tyrone Ting <kfting@nuvoton.com>
Message-id: 20240131002800.989285-4-nabihestefan@google.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This patch implements the basic registers of GMAC device and sets
registers for networking functionalities.
Squashed IRQ Implementation patch into this one for compliation.
Tested:
The following message shows up with the change:
Broadcom BCM54612E stmmac-0:00: attached PHY driver [Broadcom BCM54612E] (mii_bus:phy_addr=stmmac-0:00, irq=POLL)
stmmaceth f0802000.eth eth0: Link is Up - 1Gbps/Full - flow control rx/tx
Change-Id: If71c6d486b95edcccba109ba454870714d7e0940
Signed-off-by: Hao Wu <wuhaotsh@google.com>
Signed-off-by: Nabih Estefan Diaz <nabihestefan@google.com>
Reviewed-by: Tyrone Ting <kfting@nuvoton.com>
Message-id: 20240131002800.989285-2-nabihestefan@google.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
According to the QEMU Coding Style document:
> Do not use printf(), fprintf() or monitor_printf(). Instead, use
> error_report() or error_vreport() from error-report.h. This ensures the
> error is reported in the right place (current monitor or stderr), and in
> a uniform format.
> Use error_printf() & friends to print additional information.
This commit changes fprintfs that report warnings and errors to the
appropriate report functions.
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 42a8953553cf68e8bacada966f93af4fbce45919.1706544115.git.manos.pitsidianakis@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Tracing DPRINTFs to stderr might not be desired. A developer that relies
on tracepoints should be able to opt-in to each tracepoint and rely on
QEMU's log redirection, instead of stderr by default.
This commit converts DPRINTFs in this file that are used for tracing
into tracepoints.
Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: b000ab73022dfeb7a7ab0ee8fd0f41fb208adaf0.1706544115.git.manos.pitsidianakis@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Tracing DPRINTFs to stderr might not be desired. A developer that relies
on tracepoints should be able to opt-in to each tracepoint and rely on
QEMU's log redirection, instead of stderr by default.
This commit converts DPRINTFs in this file that are used for tracing
into tracepoints.
Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 2fbe1fbc59078e384761c932e97cfa4276a53d75.1706544115.git.manos.pitsidianakis@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Tracing DPRINTFs to stderr might not be desired. A developer that relies
on trace events should be able to opt-in to each trace event and rely on
QEMU's log redirection, instead of stderr by default.
This commit converts DPRINTFs in this file that are used for tracing
into trace events. Errors or warnings are converted to error_report and
warn_report calls.
Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: fe5e3bd54231abe933f95a24e0e88208cd8cfd8f.1706544115.git.manos.pitsidianakis@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Tracing DPRINTFs to stderr might not be desired. A developer that relies
on trace events should be able to opt-in to each trace event and rely on
QEMU's log redirection, instead of stderr by default.
This commit converts DPRINTFs in this file that are used for tracing
into trace events. DPRINTFs that report guest errors are logged with
LOG_GUEST_ERROR.
Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 799c5141c5751cf2341e1d095349612e046424a8.1706544115.git.manos.pitsidianakis@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Tracing DPRINTFs to stderr might not be desired. A developer that relies
on trace events should be able to opt-in to each trace event and rely on
QEMU's log redirection, instead of stderr by default.
This commit converts DPRINTFs in this file that are used for tracing
into trace events. DPRINTFs that report guest errors are logged with
LOG_GUEST_ERROR.#
Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 39db71dd87bf2007cf7812f3d91dde53887f1f2f.1706544115.git.manos.pitsidianakis@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
The latest version of qemu (v8.2.0-869-g7a1dc45af5) crashes when booting
the mcimx7d-sabre emulation with Linux v5.11 and later.
qemu-system-arm: ../system/memory.c:2750: memory_region_set_alias_offset: Assertion `mr->alias' failed.
Problem is that the Designware PCIe emulation accepts the full value range
for the iATU Viewport Register. However, both hardware and emulation only
support four inbound and four outbound viewports.
The Linux kernel determines the number of supported viewports by writing
0xff into the viewport register and reading the value back. The expected
value when reading the register is the highest supported viewport index.
Match that code by masking the supported viewport value range when the
register is written. With this change, the Linux kernel reports
imx6q-pcie 33800000.pcie: iATU: unroll F, 4 ob, 4 ib, align 0K, limit 4G
as expected and supported.
Fixes: d64e5eabc4 ("pci: Add support for Designware IP block")
Cc: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Nikita Ostrenkov <n.ostrenkov@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Message-id: 20240129060055.2616989-1-linux@roeck-us.net
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Leverage the common code introduced in commit c9cf636d48 ("machine:
Add a valid_cpu_types property") to check for the single valid CPU
type. Remove the now unused MachineClass::default_cpu_type field.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20240129151828.59544-10-philmd@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Leverage the common code introduced in commit c9cf636d48 ("machine:
Add a valid_cpu_types property") to check for the single valid CPU
type. Remove the now unused MachineClass::default_cpu_type field.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20240129151828.59544-9-philmd@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
The npcm7xx Soc is created with a Cortex-A9 core, see in
hw/arm/npcm7xx.c:
static void npcm7xx_init(Object *obj)
{
NPCM7xxState *s = NPCM7XX(obj);
for (int i = 0; i < NPCM7XX_MAX_NUM_CPUS; i++) {
object_initialize_child(obj, "cpu[*]", &s->cpu[i],
ARM_CPU_TYPE_NAME("cortex-a9"));
}
The MachineClass::default_cpu_type field is ignored: delete it.
Use the common code introduced in commit c9cf636d48 ("machine: Add
a valid_cpu_types property") to check for valid CPU type at the
board level.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20240129151828.59544-8-philmd@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Musca boards use the embedded subsystems (SSE) tied to a specific
Cortex core. Our models only use the Cortex-M33.
Use the common code introduced in commit c9cf636d48 ("machine: Add
a valid_cpu_types property") to check for valid CPU type at the
board level.
Remove the now unused MachineClass::default_cpu_type field.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20240129151828.59544-7-philmd@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
The M2Sxxx SoC family can only be used with Cortex-M3.
Propagating the CPU type from the board level is pointless.
Hard-code the CPU type at the SoC level.
Remove the now ignored MachineClass::default_cpu_type field.
Use the common code introduced in commit c9cf636d48 ("machine: Add
a valid_cpu_types property") to check for valid CPU type at the
board level.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20240129151828.59544-6-philmd@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Restrict MachineClass::valid_cpu_types[] to the single
valid CPU types.
Instead of ignoring invalid CPU type requested by the user:
$ qemu-system-arm -M midway -cpu cortex-a7 -S -monitor stdio
QEMU 8.2.50 monitor - type 'help' for more information
(qemu) info qom-tree
/machine (midway-machine)
/cpu[0] (cortex-a15-arm-cpu)
...
we now display an error:
$ qemu-system-arm -M midway -cpu cortex-a7
qemu-system-arm: Invalid CPU model: cortex-a7
The only valid type is: cortex-a15
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Message-id: 20240129151828.59544-5-philmd@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
QDev objects created with qdev_new() need to manually add
their parent relationship with object_property_add_child().
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Message-id: 20240129151828.59544-4-philmd@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Restrict MachineClass::valid_cpu_types[] to the single
valid CPU type.
Instead of ignoring invalid CPU type requested by the user:
$ qemu-system-arm -M nuri -cpu cortex-a7 -S -monitor stdio
QEMU 8.2.50 monitor - type 'help' for more information
(qemu) info qom-tree
/machine (nuri-machine)
/soc (exynos4210)
/cpu[0] (cortex-a9-arm-cpu)
...
We now display an error:
$ qemu-system-arm -M nuri -cpu cortex-a7
qemu-system-arm: Invalid CPU model: cortex-a7
The only valid type is: cortex-a9
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Message-id: 20240129151828.59544-3-philmd@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
QDev objects created with qdev_new() need to manually add
their parent relationship with object_property_add_child().
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Message-id: 20240129151828.59544-2-philmd@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
We can't just embed labels directly into files like qemu-options.hx which
are included from multiple top-level rST files, because Sphinx sees the
labels as duplicate: https://github.com/sphinx-doc/sphinx/issues/9707
So add an optional argument to the SRST directive which causes a label
of the form '.. _DOCNAME-HXFILE-LABEL:' to be emitted, where 'DOCNAME'
is the name of the top level rST file, 'HXFILE' is the filename of the
.hx file, and 'LABEL' is the text provided within the 'SRST()' directive.
Using the DOCNAME of the top-level rST document means that it is unique
even when the .hx file is included from two different documents, as is
the case for qemu-options.hx
Now where the Xen PV documentation refers to the documentation for the
-initrd command line option, it can emit a link directly to it as
'<system/invocation-qemu-options-initrd>'.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20240130190348.682912-1-dwmw2@infradead.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
In commit 4315f7c614 we restructured the logic for creating the
VFP related properties to avoid testing the aa32_simd_r32 feature on
AArch64 CPUs. However in the process we accidentally stopped
exposing the "vfp" QOM property on AArch32 TCG CPUs.
This mostly hasn't had any ill effects because not many people want
to disable VFP, but it wasn't intentional. Reinstate the property.
Cc: qemu-stable@nongnu.org
Fixes: 4315f7c614 ("target/arm: Restructure has_vfp_d32 test")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2098
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20240126193432.2210558-1-peter.maydell@linaro.org
This test program is the last use of any variable length array in the
codebase. If we can get rid of all uses of VLAs we can make the
compiler error on new additions. This is a defensive measure against
security bugs where an on-stack dynamic allocation isn't correctly
size-checked (e.g. CVE-2021-3527).
In this case the test code didn't even want a variable-sized
array, it was just accidentally using syntax that gave it one.
(The array size for C has to be an actual constant expression,
not just something that happens to be known to be constant...)
Remove the VLA usage.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Message-id: 20240125173211.1786196-2-peter.maydell@linaro.org
In kernel commit 5d5b4e8c2d9ec ("arm64/sve: Report FEAT_SVE_B16B16 to
userspace") Linux added ID_AA64ZFR0_el1.B16B16 to the set of ID
register fields which it exposes to userspace. Update our
exported_bits mask to include this.
(This doesn't yet change any behaviour for us, because we don't yet
have any CPUs that implement this feature, which is part of SVE2.)
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20240125134304.1470404-1-peter.maydell@linaro.org
The -serial option documentation is a bit brief about '-serial none'
and '-serial null'. In particular it's not very clear about the
difference between them, and it doesn't mention that it's up to
the machine model whether '-serial none' means "don't create the
serial port" or "don't wire the serial port up to anything".
Expand on these points.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20240122163607.459769-3-peter.maydell@linaro.org
