All 32-bit hppa CPUs allow a fixed number of TLB entries to have a
different page size than the default 4k.
Those are called "Block-TLBs" and are created at startup by the
operating system and managed by the firmware of hppa machines
through the firmware PDC_BLOCK_TLB call.
This patchset adds the necessary glue to SeaBIOS-hppa and
qemu to allow up to 16 BTLB entries in the emulation.
Two patches from Mikulas Patocka fix signal delivery issues
in linux-user on hppa.
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Merge tag 'hppa-btlb-pull-request' of https://github.com/hdeller/qemu-hppa into staging
Block-TLB support and linux-user fixes for hppa target
All 32-bit hppa CPUs allow a fixed number of TLB entries to have a
different page size than the default 4k.
Those are called "Block-TLBs" and are created at startup by the
operating system and managed by the firmware of hppa machines
through the firmware PDC_BLOCK_TLB call.
This patchset adds the necessary glue to SeaBIOS-hppa and
qemu to allow up to 16 BTLB entries in the emulation.
Two patches from Mikulas Patocka fix signal delivery issues
in linux-user on hppa.
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# =kqqt
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# gpg: Signature made Tue 19 Sep 2023 15:17:39 EDT
# gpg: using EDDSA key BCE9123E1AD29F07C049BBDEF712B510A23A0F5F
# gpg: Good signature from "Helge Deller <deller@gmx.de>" [unknown]
# gpg: aka "Helge Deller <deller@kernel.org>" [unknown]
# gpg: WARNING: This key is not certified with a trusted signature!
# gpg: There is no indication that the signature belongs to the owner.
# Primary key fingerprint: 4544 8228 2CD9 10DB EF3D 25F8 3E5F 3D04 A7A2 4603
# Subkey fingerprint: BCE9 123E 1AD2 9F07 C049 BBDE F712 B510 A23A 0F5F
* tag 'hppa-btlb-pull-request' of https://github.com/hdeller/qemu-hppa:
linux-user/hppa: lock both words of function descriptor
linux-user/hppa: clear the PSW 'N' bit when delivering signals
target/hppa: Wire up diag instruction to support BTLB
target/hppa: Extract diagnose immediate value
target/hppa: Add BTLB support to hppa TLB functions
target/hppa: Report and clear BTLBs via fw_cfg at startup
target/hppa: Allow up to 16 BTLB entries
target/hppa: Update to SeaBIOS-hppa version 9
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
The code in setup_rt_frame reads two words at haddr, but locks only one.
This patch fixes it to lock both.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Acked-by: Helge Deller <deller@gmx.de>
Cc: qemu-stable@nongnu.org
Signed-off-by: Helge Deller <deller@gmx.de>
qemu-hppa may crash when delivering a signal. It can be demonstrated with
this program. Compile the program with "hppa-linux-gnu-gcc -O2 signal.c"
and run it with "qemu-hppa -one-insn-per-tb a.out". It reports that the
address of the flag is 0xb4 and it crashes when attempting to touch it.
#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <signal.h>
sig_atomic_t flag;
void sig(int n)
{
printf("&flag: %p\n", &flag);
flag = 1;
}
int main(void)
{
struct sigaction sa;
struct itimerval it;
sa.sa_handler = sig;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_RESTART;
if (sigaction(SIGALRM, &sa, NULL)) perror("sigaction"), exit(1);
it.it_interval.tv_sec = 0;
it.it_interval.tv_usec = 100;
it.it_value.tv_sec = it.it_interval.tv_sec;
it.it_value.tv_usec = it.it_interval.tv_usec;
if (setitimer(ITIMER_REAL, &it, NULL)) perror("setitimer"), exit(1);
while (1) {
}
}
The reason for the crash is that the signal handling routine doesn't clear
the 'N' flag in the PSW. If the signal interrupts a thread when the 'N'
flag is set, the flag remains set at the beginning of the signal handler
and the first instruction of the signal handler is skipped.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Acked-by: Helge Deller <deller@gmx.de>
Cc: qemu-stable@nongnu.org
Signed-off-by: Helge Deller <deller@gmx.de>
Wire up the hppa diag instruction to support Block-TLBs
when called with the 0x100 value.
The diag_btlb() helper function does all necessary steps
to emulate the PDC BTLB firmware function, which includes
providing BTLB info, adding a new BTLB, deleting a BTLB
and removing all BTLBs.
Signed-off-by: Helge Deller <deller@gmx.de>
"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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# 9MSYZe+I2v8=
# =iraT
# -----END PGP SIGNATURE-----
# 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>
In this short queue we're making two important changes:
- Nicholas Piggin is now the qemu-ppc maintainer. Cédric Le Goater and
Daniel Barboza will act as backup during Nick's transition to this new
role.
- Support for NVIDIA V100 GPU with NVLink2 is dropped from qemu-ppc.
Linux removed the same support back in 5.13, we're following suit now.
A xive Coverity fix is also included.
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Merge tag 'pull-ppc-20230918' of https://gitlab.com/danielhb/qemu into staging
ppc patch queue for 2023-09-18:
In this short queue we're making two important changes:
- Nicholas Piggin is now the qemu-ppc maintainer. Cédric Le Goater and
Daniel Barboza will act as backup during Nick's transition to this new
role.
- Support for NVIDIA V100 GPU with NVLink2 is dropped from qemu-ppc.
Linux removed the same support back in 5.13, we're following suit now.
A xive Coverity fix is also included.
# -----BEGIN PGP SIGNATURE-----
#
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# =y3nh
# -----END PGP SIGNATURE-----
# gpg: Signature made Mon 18 Sep 2023 09:24:44 EDT
# gpg: using EDDSA key 17EBFF9923D01800AF2838193CD9CA96DE033164
# gpg: issuer "danielhb413@gmail.com"
# gpg: Good signature from "Daniel Henrique Barboza <danielhb413@gmail.com>" [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: 17EB FF99 23D0 1800 AF28 3819 3CD9 CA96 DE03 3164
* tag 'pull-ppc-20230918' of https://gitlab.com/danielhb/qemu:
spapr: Remove support for NVIDIA V100 GPU with NVLink2
ppc/xive: Fix uint32_t overflow
MAINTAINERS: Nick Piggin PPC maintainer, other PPC changes
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
When updating ioeventfds, we need to iterate all address spaces,
but some address spaces do not register eventfd_add|del call when
memory_listener_register() and they do nothing when updating ioeventfds.
So we can skip these AS in address_space_update_ioeventfds().
The overhead of memory_region_transaction_commit() can be significantly
reduced. For example, a VM with 8 vhost net devices and each one has
64 vectors, can reduce the time spent on memory_region_transaction_commit by 20%.
Message-ID: <20230830032906.12488-1-hongmianquan@bytedance.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: hongmianquan <hongmianquan@bytedance.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
For migration purposes, users might want to reuse the default RAM
backend id, but specify a different memory backend.
For example, to reuse "pc.ram" on q35, one has to set
-machine q35,memory-backend=pc.ram
Only then, can a memory backend with the id "pc.ram" be created
manually.
Let's improve the error message by improving the hint. Use
error_append_hint() -- which in turn requires ERRP_GUARD().
Message-ID: <20230906120503.359863-12-david@redhat.com>
Suggested-by: ThinerLogoer <logoerthiner1@163.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Mario Casquero <mcasquer@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
It's easy to miss that memory-backend-file with "share=off" (default)
will always try opening the file R/W as default, and fail if we don't
have write permissions to the file.
In that case, the user has to explicit specify "readonly=on,rom=off" to
get usable RAM, for example, for VM templating.
Let's hint that '-object memory-backend-file,readonly=on,rom=off,...'
exists to consume R/O files in a private mapping to create writable RAM,
but only if we have permissions to open the file read-only.
Message-ID: <20230906120503.359863-11-david@redhat.com>
Suggested-by: ThinerLogoer <logoerthiner1@163.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Let's add some details about VM templating, focusing on the VM memory
configuration only.
There is much more to VM templating (VM state? block devices?), but I leave
that as future work.
Message-ID: <20230906120503.359863-10-david@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: David Hildenbrand <david@redhat.com>
"-mem-path" corresponds to "memory-backend-file,share=off" and,
therefore, creates a private COW mapping of the file. For multi-proces
QEMU, we need proper shared file-backed memory.
Let's make that clearer.
Message-ID: <20230906120503.359863-9-david@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
open() does not fail on directories when opening them readonly (O_RDONLY).
Currently, we succeed opening such directories and fail later during
mmap(), resulting in a misleading error message.
$ ./qemu-system-x86_64 \
-object memory-backend-file,id=ram0,mem-path=tmp,readonly=true,size=1g
qemu-system-x86_64: unable to map backing store for guest RAM: No such device
To identify directories and handle them accordingly in file_ram_open()
also when readonly=true was specified, detect if we just opened a directory
using fstat() instead. Then, fail file_ram_open() right away, similarly
to how we now fail if the file does not exist and we want to open the
file readonly.
With this change, we get a nicer error message:
qemu-system-x86_64: can't open backing store tmp for guest RAM: Is a directory
Note that the only memory-backend-file will end up calling
memory_region_init_ram_from_file() -> qemu_ram_alloc_from_file() ->
file_ram_open().
Message-ID: <20230906120503.359863-8-david@redhat.com>
Reported-by: Thiner Logoer <logoerthiner1@163.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Tested-by: Mario Casquero <mcasquer@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Currently, if a file does not exist yet, file_ram_open() will create new
empty file and open it writable. However, it even does that when
readonly=true was specified.
Specifying O_RDONLY instead to create a new readonly file would
theoretically work, however, ftruncate() will refuse to resize the new
empty file and we'll get a warning:
ftruncate: Invalid argument
And later eventually more problems when actually mmap'ing that file and
accessing it.
If someone intends to let QEMU open+mmap a file read-only, better
create+resize+fill that file ahead of time outside of QEMU context.
We'll now fail with:
./qemu-system-x86_64 \
-object memory-backend-file,id=ram0,mem-path=tmp,readonly=true,size=1g
qemu-system-x86_64: can't open backing store tmp for guest RAM: No such file or directory
All use cases of readonly files (R/O NVDIMMs, VM templating) work on
existing files, so silently creating new files might just hide user
errors when accidentally specifying a non-existent file.
Note that the only memory-backend-file will end up calling
memory_region_init_ram_from_file() -> qemu_ram_alloc_from_file() ->
file_ram_open().
Move error reporting to the single caller.
Message-ID: <20230906120503.359863-7-david@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
fallocate() will fail, let's print a nicer error message.
Message-ID: <20230906120503.359863-6-david@redhat.com>
Suggested-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Let's remap with the proper protection that we can derive from
RAM_READONLY.
Message-ID: <20230906120503.359863-5-david@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: David Hildenbrand <david@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>
There is a difference between how we open a file and how we mmap it,
and we want to support writable private mappings of readonly files. Let's
define RAM_READONLY and RAM_READONLY_FD flags, to replace the single
"readonly" parameter for file-related functions.
In memory_region_init_ram_from_fd() and memory_region_init_ram_from_file(),
initialize mr->readonly based on the new RAM_READONLY flag.
While at it, add some RAM_* flags we missed to add to the list of accepted
flags in the documentation of some functions.
No change in functionality intended. We'll make use of both flags next
and start setting them independently for memory-backend-file.
Message-ID: <20230906120503.359863-3-david@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Currently, when using a true R/O NVDIMM (ROM memory backend) with a label
area, the VM can easily crash QEMU by trying to write to the label area,
because the ROM memory is mmap'ed without PROT_WRITE.
[root@vm-0 ~]# ndctl disable-region region0
disabled 1 region
[root@vm-0 ~]# ndctl zero-labels nmem0
-> QEMU segfaults
Let's remember whether we have a ROM memory backend and properly
reject the write request:
[root@vm-0 ~]# ndctl disable-region region0
disabled 1 region
[root@vm-0 ~]# ndctl zero-labels nmem0
zeroed 0 nmem
In comparison, on a system with a R/W NVDIMM:
[root@vm-0 ~]# ndctl disable-region region0
disabled 1 region
[root@vm-0 ~]# ndctl zero-labels nmem0
zeroed 1 nmem
For ACPI, just return "unsupported", like if no label exists. For spapr,
return "H_P2", similar to when no label area exists.
Could we rely on the "unarmed" property? Maybe, but it looks cleaner to
only disallow what certainly cannot work.
After all "unarmed=on" primarily means: cannot accept persistent writes. In
theory, there might be setups where devices with "unarmed=on" set could
be used to host non-persistent data (temporary files, system RAM, ...); for
example, in Linux, admins can overwrite the "readonly" setting and still
write to the device -- which will work as long as we're not using ROM.
Allowing writing label data in such configurations can make sense.
Message-ID: <20230906120503.359863-2-david@redhat.com>
Fixes: dbd730e859 ("nvdimm: check -object memory-backend-file, readonly=on option")
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
NVLink2 support was removed from the PPC PowerNV platform and VFIO in
Linux 5.13 with commits :
562d1e207d32 ("powerpc/powernv: remove the nvlink support")
b392a1989170 ("vfio/pci: remove vfio_pci_nvlink2")
This was 2.5 years ago. Do the same in QEMU with a revert of commit
ec132efaa8 ("spapr: Support NVIDIA V100 GPU with NVLink2"). Some
adjustements are required on the NUMA part.
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Message-ID: <20230918091717.149950-1-clg@kaod.org>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
As reported by Coverity, "idx << xive->pc_shift" is evaluated using
32-bit arithmetic, and then used in a context expecting a "uint64_t".
Add a uint64_t cast.
Fixes: Coverity CID 1519049
Fixes: b68147b7a5 ("ppc/xive: Add support for the PC MMIOs")
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Frederic Barrat <fbarrat@linux.ibm.com>
Message-ID: <20230914154650.222111-1-clg@kaod.org>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Update all relevant PowerPC entries as follows:
- Nick Piggin is promoted to Maintainer in all qemu-ppc subsystems.
Nick has been a solid contributor for the last couple of years and
has the required knowledge and motivation to drive the boat.
- Greg Kurz is being removed from all qemu-ppc entries. Greg has moved
to other areas of interest and will retire from qemu-ppc. Thanks Mr
Kurz for all the years of service.
- David Gibson was removed as 'Reviewer' from PowerPC TCG CPUs and PPC
KVM CPUs. Change done per his request.
- Daniel Barboza downgraded from 'Maintainer' to 'Reviewer' in sPAPR and
PPC KVM CPUs. It has been a long since I last touched those areas and
it's not justified to be kept as maintainer in them.
- Cedric Le Goater and Daniel Barboza removed as 'Reviewer' in VOF. We
don't have the required knowledge to justify it.
- VOF support downgraded from 'Maintained' to 'Odd Fixes' since it
better reflects the current state of the subsystem.
Acked-by: Cédric Le Goater <clg@kaod.org>
Acked-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Acked-by: Nicholas Piggin <npiggin@gmail.com>
Message-ID: <20230915110507.194762-1-danielhb413@gmail.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Use a heap allocation instead of a variable length array in
tap_receive_iov().
The codebase has very few VLAs, and if we can get rid of them all 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).
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Francisco Iglesias <frasse.iglesias@gmail.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Use a g_autofree heap allocation instead of a variable length
array in dump_receive_iov().
The codebase has very few VLAs, and if we can get rid of them all 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).
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Francisco Iglesias <frasse.iglesias@gmail.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Replace an on-stack variable length array in of_dpa_ig() with
a g_autofree heap allocation.
The codebase has very few VLAs, and if we can get rid of them all 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).
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Francisco Iglesias <frasse.iglesias@gmail.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
In fill_rx_bd() we create a variable length array of size
etsec->rx_padding. In fact we know that this will never be
larger than 64 bytes, because rx_padding is set in rx_init_frame()
in a way that ensures it is only that large. Use a fixed sized
array and assert that it is big enough.
Since padd[] is now potentially rather larger than the actual
padding required, adjust the memset() we do on it to match the
size that we write with cpu_physical_memory_write(), rather than
clearing the entire array.
The codebase has very few VLAs, and if we can get rid of them all 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).
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Jason Wang <jasowang@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>
This pulls in the fixes for libasan version as well as support for
libxdp that will be used for af-xdp netdev in the next commits.
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Rename e1000e_ba_state according and e1000e_write_hdr_to_rx_buffers for
consistency with IGB.
Signed-off-by: Tomasz Dzieciol <t.dzieciol@partner.samsung.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Tested-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Packet-split descriptors are used by Linux VF driver for MTU values from 2048
Signed-off-by: Tomasz Dzieciol <t.dzieciol@partner.samsung.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Tested-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Refactoring is done in preparation for support of multiple advanced
descriptors RX modes, especially packet-split modes.
Signed-off-by: Tomasz Dzieciol <t.dzieciol@partner.samsung.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Tested-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Refactoring is done in preparation for support of multiple advanced
descriptors RX modes, especially packet-split modes.
Signed-off-by: Tomasz Dzieciol <t.dzieciol@partner.samsung.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Tested-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Rename E1000E_RingInfo_st and E1000E_RingInfo according to qemu typdefs guide.
Signed-off-by: Tomasz Dzieciol <t.dzieciol@partner.samsung.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Tested-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
TCP ACK detection is no longer present in igb.
Signed-off-by: Tomasz Dzieciol <t.dzieciol@partner.samsung.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Tested-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
USO features of virtio-net device depend on kernel ability
to support them, for backward compatibility by default the
features are disabled on 8.0 and earlier.
Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com>
Signed-off-by: Andrew Melnychecnko <andrew@daynix.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
New features are subject to check with vhost-user and vdpa.
Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com>
Signed-off-by: Andrew Melnychenko <andrew@daynix.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Tap indicates support for USO features according to
capabilities of current kernel module.
Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com>
Signed-off-by: Andrew Melnychecnko <andrew@daynix.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Passing additional parameters (USOv4 and USOv6 offloads) when
setting TAP offloads
Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com>
Signed-off-by: Andrew Melnychenko <andrew@daynix.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Stefan Hajnoczi