shm_open() creates and opens a new POSIX shared memory object.
A POSIX shared memory object allows creating memory backend with an
associated file descriptor that can be shared with external processes
(e.g. vhost-user).
The new `memory-backend-shm` can be used as an alternative when
`memory-backend-memfd` is not available (Linux only), since shm_open()
should be provided by any POSIX-compliant operating system.
This backend mimics memfd, allocating memory that is practically
anonymous. In theory shm_open() requires a name, but this is allocated
for a short time interval and shm_unlink() is called right after
shm_open(). After that, only fd is shared with external processes
(e.g., vhost-user) as if it were associated with anonymous memory.
In the future we may also allow the user to specify the name to be
passed to shm_open(), but for now we keep the backend simple, mimicking
anonymous memory such as memfd.
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com> (QAPI schema)
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-Id: <20240618100519.145853-1-sgarzare@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
As module-level topology support is added to X86CPU, now we can enable
the support for the modules parameter on PC machines. With this support,
we can define a 5-level x86 CPU topology with "-smp":
-smp cpus=*,maxcpus=*,sockets=*,dies=*,modules=*,cores=*,threads=*.
So, add the 5-level topology example in description of "-smp".
Additionally, add the missed drawers and books options in previous
example.
Tested-by: Yongwei Ma <yongwei.ma@intel.com>
Co-developed-by: Zhuocheng Ding <zhuocheng.ding@intel.com>
Signed-off-by: Zhuocheng Ding <zhuocheng.ding@intel.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
Message-ID: <20240424154929.1487382-19-zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The old "-runas" option has the disadvantage that it is not visible
in the QAPI schema, so it is not available via the normal introspection
mechanisms. We've recently introduced the "-run-with" option for exactly
this purpose, which is meant to handle the options that affect the
runtime behavior. Thus let's introduce a "user=..." parameter here now
and deprecate the old "-runas" option.
Message-ID: <20240506112058.51446-1-thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>
The whole RDMA subsystem was deprecated in commit e9a54265f5
("hw/rdma: Deprecate the pvrdma device and the rdma subsystem")
released in v8.2.
Remove:
- PVRDMA device
- generated vmw_pvrdma/ directory from linux-headers
- rdmacm-mux tool from contrib/
Cc: Yuval Shaia <yuval.shaia.ml@gmail.com>
Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20240328130255.52257-2-philmd@linaro.org>
The Nios II target is deprecated since v8.2 in commit 9997771bc1
("target/nios2: Deprecate the Nios II architecture").
Remove:
- Buildsys / CI infra
- User emulation
- System emulation (10m50-ghrd & nios2-generic-nommu machines)
- Tests
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Acked-by: Marek Vasut <marex@denx.de>
Message-Id: <20240327144806.11319-3-philmd@linaro.org>
Fix the unit typo of interleave-granularity of CXL Fixed Memory
Window in qemu-option.hx.
Fixes: 03b39fcf64 ("hw/cxl: Make the CFMW a machine parameter.")
Signed-off-by: Yuquan Wang wangyuquan1236@phytium.com.cn
Message-ID: <20240407083539.1488172-2-wangyuquan1236@phytium.com.cn>
[PMD: Reworded]
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Document the new aw-bits option.
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Message-Id: <20240307134445.92296-10-eric.auger@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
We are missing an entry for the virtio-iommu-pci device. Add the
information on which machine it is currently supported and document
the new granule option.
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Message-Id: <20240307134445.92296-5-eric.auger@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Felix Wu <flwu@google.com>
Signed-off-by: Nabih Estefan <nabihestefan@google.com>
Message-Id: <20240221170027.1027325-3-nabihestefan@google.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Version 2.1+.
Signed-off-by: Felix Wu <flwu@google.com>
Signed-off-by: Nabih Estefan <nabihestefan@google.com>
Message-Id: <20240221170027.1027325-2-nabihestefan@google.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Before v2.12, the implementation of serial ports was limited to
a value of MAX_SERIAL_PORTS = 4. We now dynamically allocate
the data structures for serial ports, so this limit is no longer
present, but the documentation for the -serial options still reads:
"This option can be used several times to simulate up to 4 serial ports."
Update to "This option can be used several times to simulate
multiple serial ports." to avoid misleading.
Signed-off-by: Steven Shen <steven.shen@jaguarmicro.com>
Message-id: 20240305013016.2268-1-steven.shen@jaguarmicro.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
[PMM: tweaked commit message]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Add a fd-bootchk property to PC machine types, so that -no-fd-bootchk
returns an error if the machine does not support booting from floppies
and checking for boot signatures therein.
Suggested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Correct typos automatically found with the `typos` tool
<https://crates.io/crates/typos>
Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
The detailed help lists zoom-to-fit as valid option but it is missing
from the short option summary. Add it there too.
Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
With SMBIOS support added for RISC-V we also should enable the command line
option.
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Message-ID: <20240123184229.10415-5-heinrich.schuchardt@canonical.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
For RISC-V the SMBIOS standard requires specific values of the processor
family value depending on the bitness of the CPU.
Add a processor-family option for SMBIOS table 4.
The value of processor-family may exceed 255 and therefore must be provided
in the Processor Family 2 field. Set the Processor Family field to 0xFE
which signals that the Processor Family 2 is used.
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Message-ID: <20240123184229.10415-2-heinrich.schuchardt@canonical.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
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>
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
There's no need to repeat script=/etc/qemu-ifup in examples,
as it is already in there. More, all examples uses incorrect
"down script=" (which should be "downscript=").
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Reviewed-by: Zhang Chen <chen.zhang@intel.com>
This option has been deprecated before the 8.1 release,
in commit 12fd0f41d0 ("Document that -singlestep command
line option is deprecated"). Time to drop it.
Inspired-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240117151430.29235-4-philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>
It's been marked as deprecated since QEMU 8.1, so it should be fine
to remove this now.
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240118103759.130748-5-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
It's been marked as deprecated since QEMU 8.1 (and was only available
since QEMU 8.0 anyway), so it should be fine to remove this now.
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240118103759.130748-4-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
It's been marked as deprecated since QEMU 8.0, so it should be fine
to remove this now.
Message-ID: <20240118103759.130748-3-thuth@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Thomas Huth <thuth@redhat.com>
It's been marked as deprecated since QEMU 8.0, so it should be fine
to remove this now.
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240118103759.130748-2-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
This allows passing the KVM device node to use as a file
descriptor via /dev/fdset/XX. Passing the device node to
use as a file descriptor allows running qemu unprivileged
even when the user running qemu is not in the kvm group
on distributions where access to /dev/kvm is gated behind
membership of the kvm group (as long as the process invoking
qemu is able to open /dev/kvm and passes the file descriptor
to qemu).
Signed-off-by: Daan De Meyer <daan.j.demeyer@gmail.com>
Message-ID: <20231021134015.1119597-1-daan.j.demeyer@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
We don't currently document the syntax of .hx files anywhere
except in a few comments at the top of individual .hx files.
We don't even have somewhere in the developer docs where we
could do this.
Add a new files docs/devel/docs.rst which can be a place to
document how our docs build process works. For the moment,
put in only a brief introductory paragraph and the documentation
of the .hx files. We could later add to this file by for
example describing how the QAPI-schema-to-docs process works,
or anything else that developers might need to know about
how to add documentation.
Make the .hx files refer to this doc file, and clean
up their header comments to be more accurate for the
usage in each file and less cut-n-pasted.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Luc Michel <luc.michel@amd.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Message-id: 20231212162313.1742462-1-peter.maydell@linaro.org
Some options for -display cocoa were not described or not listed at all.
Reported-by: BALATON Zoltan <balaton@eik.bme.hu>
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Apparently the help entries were not merged when the patches got in.
Fixes: f844cdb997 ("ui/cocoa: capture all keys and combos when mouse is grabbed")
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
* Some header clean-ups by Philippe
* Restrict type names to alphanumerical range (and a few special characters)
* Fix analyze-migration.py script on s390x
* Clean up and improve some tests
* Document handling of commas in CLI options parameters
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Merge tag 'pull-request-2023-12-20' of https://gitlab.com/thuth/qemu into staging
* Add compat machines for QEMU 9.0
* Some header clean-ups by Philippe
* Restrict type names to alphanumerical range (and a few special characters)
* Fix analyze-migration.py script on s390x
* Clean up and improve some tests
* Document handling of commas in CLI options parameters
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# gpg: Signature made Wed 20 Dec 2023 04:36:11 EST
# gpg: using RSA key 27B88847EEE0250118F3EAB92ED9D774FE702DB5
# gpg: issuer "thuth@redhat.com"
# gpg: Good signature from "Thomas Huth <th.huth@gmx.de>" [full]
# gpg: aka "Thomas Huth <thuth@redhat.com>" [full]
# gpg: aka "Thomas Huth <huth@tuxfamily.org>" [full]
# gpg: aka "Thomas Huth <th.huth@posteo.de>" [unknown]
# Primary key fingerprint: 27B8 8847 EEE0 2501 18F3 EAB9 2ED9 D774 FE70 2DB5
* tag 'pull-request-2023-12-20' of https://gitlab.com/thuth/qemu:
tests/unit/test-qmp-event: Replace fixture by global variables
tests/unit/test-qmp-event: Simplify event emission check
tests/unit/test-qmp-event: Drop superfluous mutex
tests/qtest/npcm7xx_pwm-test: Only do full testing in slow mode
qemu-options: Clarify handling of commas in options parameters
tests/qtest/migration-test: Fix analyze-migration.py for s390x
qom/object: Limit type names to alphanumerical and some few special characters
tests/unit/test-io-task: Rename "qemu:dummy" to avoid colon in the name
memory: Remove "qemu:" prefix from the "qemu:ram-discard-manager" type name
hw: Replace anti-social QOM type names (again)
docs/system/arm: Fix for rename of type "xlnx.bbram-ctrl"
target: Restrict 'sysemu/reset.h' to system emulation
hw/s390x/ipl: Remove unused 'exec/exec-all.h' included header
hw/misc/mips_itu: Remove unnecessary 'exec/exec-all.h' header
hw/ppc/spapr_hcall: Remove unused 'exec/exec-all.h' included header
system/qtest: Restrict QTest API to system emulation
system/qtest: Include missing 'hw/core/cpu.h' header
MAINTAINERS: Add some more vmware-related files to the corresponding section
hw: Add compat machines for 9.0
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Provide explicit guidance on dealing with option parameters as arbitrary
strings containing commas, such as in "file=my,file" and "string=a,b". The
updated documentation emphasizes the need to double commas when they
appear within such parameters.
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1839
Signed-off-by: Yihuan Pan <xun794@gmail.com>
Message-ID: <20231213141706.629833-2-xun794@gmail.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Introduce an iommufd object which allows the interaction
with the host /dev/iommu device.
The /dev/iommu can have been already pre-opened outside of qemu,
in which case the fd can be passed directly along with the
iommufd object:
This allows the iommufd object to be shared accross several
subsystems (VFIO, VDPA, ...). For example, libvirt would open
the /dev/iommu once.
If no fd is passed along with the iommufd object, the /dev/iommu
is opened by the qemu code.
Suggested-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Add notes about console and network support, and how to launch PV guests.
Clean up the disk configuration examples now that that's simpler, and
remove the comment about IDE unplug on q35/AHCI now that it's fixed.
Update the -initrd option documentation to explain how to quote commas
in module command lines, and reference it when documenting PV guests.
Also update stale avocado test filename in MAINTAINERS.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
When the discard-no-unref flag is enabled, we keep the reference for
normal discard requests.
But when a discard is executed on a snapshot/qcow2 image with backing,
the discards are saved as zero clusters in the snapshot image.
When committing the snapshot to the backing file, not
discard_in_l2_slice is called but zero_in_l2_slice. Which did not had
any logic to keep the reference when discard-no-unref is enabled.
Therefor we add logic in the zero_in_l2_slice call to keep the reference
on commit.
Fixes: https://gitlab.com/qemu-project/qemu/-/issues/1621
Signed-off-by: Jean-Louis Dupond <jean-louis@dupond.be>
Message-Id: <20231003125236.216473-2-jean-louis@dupond.be>
[hreitz: Made the documentation change more verbose, as discussed
on-list]
Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
S390 adds two new SMP levels, drawers and books to the CPU
topology.
S390 CPUs have specific topology features like dedication and
entitlement. These indicate to the guest information on host
vCPU scheduling and help the guest make better scheduling decisions.
Add the new levels to the relevant QAPI structs.
Add all the supported topology levels, dedication and entitlement
as properties to S390 CPUs.
Create machine-common.json so we can later include it in
machine-target.json also.
Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Co-developed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Message-ID: <20231016183925.2384704-3-nsg@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
If "-audio BACKEND" is used without a model, the resulting backend
will be used whenever the audiodev property is not specified.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Allow an offset option to be specified as part of the file URI, in
the form "file:filename,offset=offset", where offset accepts the common
size suffixes, or the 0x prefix, but not both. Migration data is written
to and read from the file starting at offset. If unspecified, it defaults
to 0.
This is needed by libvirt to store its own data at the head of the file.
Suggested-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <1694182931-61390-3-git-send-email-steven.sistare@oracle.com>
Extend the migration URI to support file:<filename>. This can be used for
any migration scenario that does not require a reverse path. It can be
used as an alternative to 'exec:cat > file' in minimized containers that
do not contain /bin/sh, and it is easier to use than the fd:<fdname> URI.
It can be used in HMP commands, and as a qemu command-line parameter.
For best performance, guest ram should be shared and x-ignore-shared
should be true, so guest pages are not written to the file, in which case
the guest may remain running. If ram is not so configured, then the user
is advised to stop the guest first. Otherwise, a busy guest may re-dirty
the same page, causing it to be appended to the file multiple times,
and the file may grow unboundedly. That issue is being addressed in the
"fixed-ram" patch series.
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Tested-by: Michael Galaxy <mgalaxy@akamai.com>
Reviewed-by: Michael Galaxy <mgalaxy@akamai.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <1694182931-61390-2-git-send-email-steven.sistare@oracle.com>
These have been deprecated for a long time, and the introduction of
-audio in 7.1.0 has cemented the new way of specifying an audio backend's
parameters. However, there is still a need for simple configuration
of the audio backend in the desktop case; therefore, if no audiodev is
passed to audio_init(), go through a bunch of simple Audiodev* structures
and pick the first that can be initialized successfully.
The only QEMU_AUDIO_* option that is left in, waiting for a better idea,
is QEMU_AUDIO_DRV=none which is used by qtest.
Remove all the parsing code, including the concept of "can_be_default"
audio drivers: now that audio_prio_list[] is only used in a single place,
wav can be excluded directly in that function.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
"Host Memory Backends" and "Memory devices" queue ("mem"):
- Support and document VM templating with R/O files using a new "rom"
parameter for memory-backend-file
- Some cleanups and fixes around NVDIMMs and R/O file handling for guest
RAM
- Optimize ioeventfd updates by skipping address spaces that are not
applicable
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Merge tag 'mem-2023-09-19' of https://github.com/davidhildenbrand/qemu into staging
Hi,
"Host Memory Backends" and "Memory devices" queue ("mem"):
- Support and document VM templating with R/O files using a new "rom"
parameter for memory-backend-file
- Some cleanups and fixes around NVDIMMs and R/O file handling for guest
RAM
- Optimize ioeventfd updates by skipping address spaces that are not
applicable
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# gpg: Signature made Tue 19 Sep 2023 06:25:45 EDT
# gpg: using RSA key 1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A
# gpg: issuer "david@redhat.com"
# gpg: Good signature from "David Hildenbrand <david@redhat.com>" [unknown]
# gpg: aka "David Hildenbrand <davidhildenbrand@gmail.com>" [full]
# gpg: aka "David Hildenbrand <hildenbr@in.tum.de>" [unknown]
# gpg: WARNING: The key's User ID is not certified with a trusted signature!
# gpg: There is no indication that the signature belongs to the owner.
# Primary key fingerprint: 1BD9 CAAD 735C 4C3A 460D FCCA 4DDE 10F7 00FF 835A
* tag 'mem-2023-09-19' of https://github.com/davidhildenbrand/qemu:
memory: avoid updating ioeventfds for some address_space
machine: Improve error message when using default RAM backend id
softmmu/physmem: Hint that "readonly=on,rom=off" exists when opening file R/W for private mapping fails
docs: Start documenting VM templating
docs: Don't mention "-mem-path" in multi-process.rst
softmmu/physmem: Never return directories from file_ram_open()
softmmu/physmem: Fail creation of new files in file_ram_open() with readonly=true
softmmu/physmem: Bail out early in ram_block_discard_range() with readonly files
softmmu/physmem: Remap with proper protection in qemu_ram_remap()
backends/hostmem-file: Add "rom" property to support VM templating with R/O files
softmmu/physmem: Distinguish between file access mode and mmap protection
nvdimm: Reject writing label data to ROM instead of crashing QEMU
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
For now, "share=off,readonly=on" would always result in us opening the
file R/O and mmap'ing the opened file MAP_PRIVATE R/O -- effectively
turning it into ROM.
Especially for VM templating, "share=off" is a common use case. However,
that use case is impossible with files that lack write permissions,
because "share=off,readonly=on" will not give us writable RAM.
The sole user of ROM via memory-backend-file are R/O NVDIMMs, but as we
have users (Kata Containers) that rely on the existing behavior --
malicious VMs should not be able to consume COW memory for R/O NVDIMMs --
we cannot change the semantics of "share=off,readonly=on"
So let's add a new "rom" property with on/off/auto values. "auto" is
the default and what most people will use: for historical reasons, to not
change the old semantics, it defaults to the value of the "readonly"
property.
For VM templating, one can now use:
-object memory-backend-file,share=off,readonly=on,rom=off,...
But we'll disallow:
-object memory-backend-file,share=on,readonly=on,rom=off,...
because we would otherwise get an error when trying to mmap the R/O file
shared and writable. An explicit error message is cleaner.
We will also disallow for now:
-object memory-backend-file,share=off,readonly=off,rom=on,...
-object memory-backend-file,share=on,readonly=off,rom=on,...
It's not harmful, but also not really required for now.
Alternatives that were abandoned:
* Make "unarmed=on" for the NVDIMM set the memory region container
readonly. We would still see a change of ROM->RAM and possibly run
into memslot limits with vhost-user. Further, there might be use cases
for "unarmed=on" that should still allow writing to that memory
(temporary files, system RAM, ...).
* Add a new "readonly=on/off/auto" parameter for NVDIMMs. Similar issues
as with "unarmed=on".
* Make "readonly" consume "on/off/file" instead of being a 'bool' type.
This would slightly changes the behavior of the "readonly" parameter:
values like true/false (as accepted by a 'bool'type) would no longer be
accepted.
Message-ID: <20230906120503.359863-4-david@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
AF_XDP is a network socket family that allows communication directly
with the network device driver in the kernel, bypassing most or all
of the kernel networking stack. In the essence, the technology is
pretty similar to netmap. But, unlike netmap, AF_XDP is Linux-native
and works with any network interfaces without driver modifications.
Unlike vhost-based backends (kernel, user, vdpa), AF_XDP doesn't
require access to character devices or unix sockets. Only access to
the network interface itself is necessary.
This patch implements a network backend that communicates with the
kernel by creating an AF_XDP socket. A chunk of userspace memory
is shared between QEMU and the host kernel. 4 ring buffers (Tx, Rx,
Fill and Completion) are placed in that memory along with a pool of
memory buffers for the packet data. Data transmission is done by
allocating one of the buffers, copying packet data into it and
placing the pointer into Tx ring. After transmission, device will
return the buffer via Completion ring. On Rx, device will take
a buffer form a pre-populated Fill ring, write the packet data into
it and place the buffer into Rx ring.
AF_XDP network backend takes on the communication with the host
kernel and the network interface and forwards packets to/from the
peer device in QEMU.
Usage example:
-device virtio-net-pci,netdev=guest1,mac=00:16:35:AF:AA:5C
-netdev af-xdp,ifname=ens6f1np1,id=guest1,mode=native,queues=1
XDP program bridges the socket with a network interface. It can be
attached to the interface in 2 different modes:
1. skb - this mode should work for any interface and doesn't require
driver support. With a caveat of lower performance.
2. native - this does require support from the driver and allows to
bypass skb allocation in the kernel and potentially use
zero-copy while getting packets in/out userspace.
By default, QEMU will try to use native mode and fall back to skb.
Mode can be forced via 'mode' option. To force 'copy' even in native
mode, use 'force-copy=on' option. This might be useful if there is
some issue with the driver.
Option 'queues=N' allows to specify how many device queues should
be open. Note that all the queues that are not open are still
functional and can receive traffic, but it will not be delivered to
QEMU. So, the number of device queues should generally match the
QEMU configuration, unless the device is shared with something
else and the traffic re-direction to appropriate queues is correctly
configured on a device level (e.g. with ethtool -N).
'start-queue=M' option can be used to specify from which queue id
QEMU should start configuring 'N' queues. It might also be necessary
to use this option with certain NICs, e.g. MLX5 NICs. See the docs
for examples.
In a general case QEMU will need CAP_NET_ADMIN and CAP_SYS_ADMIN
or CAP_BPF capabilities in order to load default XSK/XDP programs to
the network interface and configure BPF maps. It is possible, however,
to run with no capabilities. For that to work, an external process
with enough capabilities will need to pre-load default XSK program,
create AF_XDP sockets and pass their file descriptors to QEMU process
on startup via 'sock-fds' option. Network backend will need to be
configured with 'inhibit=on' to avoid loading of the program.
QEMU will need 32 MB of locked memory (RLIMIT_MEMLOCK) per queue
or CAP_IPC_LOCK.
There are few performance challenges with the current network backends.
First is that they do not support IO threads. This means that data
path is handled by the main thread in QEMU and may slow down other
work or may be slowed down by some other work. This also means that
taking advantage of multi-queue is generally not possible today.
Another thing is that data path is going through the device emulation
code, which is not really optimized for performance. The fastest
"frontend" device is virtio-net. But it's not optimized for heavy
traffic either, because it expects such use-cases to be handled via
some implementation of vhost (user, kernel, vdpa). In practice, we
have virtio notifications and rcu lock/unlock on a per-packet basis
and not very efficient accesses to the guest memory. Communication
channels between backend and frontend devices do not allow passing
more than one packet at a time as well.
Some of these challenges can be avoided in the future by adding better
batching into device emulation or by implementing vhost-af-xdp variant.
There are also a few kernel limitations. AF_XDP sockets do not
support any kinds of checksum or segmentation offloading. Buffers
are limited to a page size (4K), i.e. MTU is limited. Multi-buffer
support implementation for AF_XDP is in progress, but not ready yet.
Also, transmission in all non-zero-copy modes is synchronous, i.e.
done in a syscall. That doesn't allow high packet rates on virtual
interfaces.
However, keeping in mind all of these challenges, current implementation
of the AF_XDP backend shows a decent performance while running on top
of a physical NIC with zero-copy support.
Test setup:
2 VMs running on 2 physical hosts connected via ConnectX6-Dx card.
Network backend is configured to open the NIC directly in native mode.
The driver supports zero-copy. NIC is configured to use 1 queue.
Inside a VM - iperf3 for basic TCP performance testing and dpdk-testpmd
for PPS testing.
iperf3 result:
TCP stream : 19.1 Gbps
dpdk-testpmd (single queue, single CPU core, 64 B packets) results:
Tx only : 3.4 Mpps
Rx only : 2.0 Mpps
L2 FWD Loopback : 1.5 Mpps
In skb mode the same setup shows much lower performance, similar to
the setup where pair of physical NICs is replaced with veth pair:
iperf3 result:
TCP stream : 9 Gbps
dpdk-testpmd (single queue, single CPU core, 64 B packets) results:
Tx only : 1.2 Mpps
Rx only : 1.0 Mpps
L2 FWD Loopback : 0.7 Mpps
Results in skb mode or over the veth are close to results of a tap
backend with vhost=on and disabled segmentation offloading bridged
with a NIC.
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> (docker/lcitool)
Signed-off-by: Jason Wang <jasowang@redhat.com>
Now that we have Eager Page Split support added for ARM in the kernel,
enable it in Qemu. This adds,
-eager-split-size to -accel sub-options to set the eager page split chunk size.
-enable KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE.
The chunk size specifies how many pages to break at a time, using a
single allocation. Bigger the chunk size, more pages need to be
allocated ahead of time.
Reviewed-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Message-id: 20230905091246.1931-1-shameerali.kolothum.thodi@huawei.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
