Address Space IDs allows the VDUSE framework to support devices able to
expose different virtqueues to different part of the drivers. For
example, to let QEMU handle the net device control virtqueue, so QEMU
always knows the state of the device like mac address or number of
queues enabled, while leaving the dataplane passthrough to the guest
intact. This enables live migration.
Expands the VDUSE documentation to explain how to use the new ioctls or
the new struct members of old ioctls.
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260119143306.1818855-14-eperezma@redhat.com>
Finalize the series by advertising VDUSE API v1 support to userspace.
Now that all required infrastructure for v1 (ASIDs, VQ groups,
update_iotlb_v2) is in place, VDUSE devices can opt in to the new
features.
Assume API version 0 if the VDUSE instance does not call
VDUSE_GET_API_VERSION to maintain compatibility.
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260119143306.1818855-13-eperezma@redhat.com>
Add support for assigning Address Space Identifiers (ASIDs) to each VQ
group. This enables mapping each group into a distinct memory space.
The vq group to ASID association is protected by a rwlock now. But the
mutex domain_lock keeps protecting the domains of all ASIDs, as some
operations like the one related with the bounce buffer size still
requires to lock all the ASIDs.
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260119143306.1818855-12-eperezma@redhat.com>
The next patch adds new ioctl with the ASID member per entry. Abstract
these two so it can be build on top easily.
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260119143306.1818855-11-eperezma@redhat.com>
The function vduse_dev_alloc_coherent will be called under rwlock in
next patches. Make it out of the lock to avoid increasing its fail
rate.
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260119143306.1818855-10-eperezma@redhat.com>
We will modify the function in next patches so let's clean it first.
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260119143306.1818855-9-eperezma@redhat.com>
Next patches introduce more error paths in this function. Refactor it
so they can be accommodated through gotos.
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Xie Yongji <xieyongji@bytedance.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260119143306.1818855-8-eperezma@redhat.com>
Only vdpa_sim support it. Forbid this behaviour as there is no use for
it right now, we can always enable it in the future with a feature flag.
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260119143306.1818855-7-eperezma@redhat.com>
Document that the function races with the check of DRIVER_OK.
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260119143306.1818855-6-eperezma@redhat.com>
Return the internal struct that represents the vq group as virtqueue map
token, instead of the device. This allows the map functions to access
the information per group.
At this moment all the virtqueues share the same vq group, that only
can point to ASID 0. This change prepares the infrastructure for actual
per-group address space handling
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260119143306.1818855-5-eperezma@redhat.com>
This allows separate the different virtqueues in groups that shares the
same address space. Asking the VDUSE device for the groups of the vq at
the beginning as they're needed for the DMA API.
Allocating 3 vq groups as net is the device that need the most groups:
* Dataplane (guest passthrough)
* CVQ
* Shadowed vrings.
Future versions of the series can include dynamic allocation of the
groups array so VDUSE can declare more groups.
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Xie Yongji <xieyongji@bytedance.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260119143306.1818855-4-eperezma@redhat.com>
This allows the kernel to detect whether the userspace VDUSE device
supports the VQ group and ASID features. VDUSE devices that don't set
the V1 API will not receive the new messages, and vdpa device will be
created with only one vq group and asid.
The next patches implement the new feature incrementally, only enabling
the VDUSE device to set the V1 API version by the end of the series.
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Xie Yongji <xieyongji@bytedance.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260119143306.1818855-3-eperezma@redhat.com>
Remove duplication by consolidating these here. This reduces the
posibility of a parent driver missing them.
While we're at it, fix a bug in vdpa_sim where a valid ASID can be
assigned to a group equal to ngroups, causing an out of bound write.
Cc: stable@vger.kernel.org
Fixes: bda324fd03 ("vdpasim: control virtqueue support")
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260119143306.1818855-2-eperezma@redhat.com>
Currently, cacheline group macros trigger checkpatch warnings.
For example:
$ ./scripts/checkpatch.pl -g ba7e025a6c84aed012421468d83639e5dae982b0
WARNING: Missing a blank line after declarations
#58: FILE: drivers/gpio/gpio-virtio.c:32:
+ struct virtio_gpio_response res;
+ __dma_from_device_group_end();
$ ./scripts/checkpatch.pl -g 5d4cc87414
WARNING: Missing a blank line after declarations
#267: FILE: include/net/sock.h:431:
+ int sk_rcvlowat;
+ __cacheline_group_end(sock_read_rx);
But these are not actually statements - the following macros
all expand to zero-length fields:
__cacheline_group_begin()
__cacheline_group_end()
__cacheline_group_begin_aligned()
__cacheline_group_end_aligned()
__dma_from_device_group_begin()
__dma_from_device_group_end()
Add them to $declaration_macros so checkpatch recognizes this fact.
Message-ID: <b345bb7e2d4e23672e3e5d1b283754dc11c7d8cd.1767647872.git.mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reorder struct virtio_gpio_line fields to place the DMA buffers
(req/res) last.
This eliminates the padding from aligning struct size on
ARCH_DMA_MINALIGN.
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Message-ID: <f1221bbc120df6adaba9006710a517f1e84a10b2.1767601130.git.mst@redhat.com>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
The res and ires buffers in struct virtio_gpio_line and struct
vgpio_irq_line respectively are used for DMA_FROM_DEVICE via
virtqueue_add_sgs(). However, within these structs, even though these
elements are tagged as ____cacheline_aligned, adjacent struct elements
can share DMA cachelines on platforms where ARCH_DMA_MINALIGN >
L1_CACHE_BYTES (e.g., arm64 with 128-byte DMA alignment but 64-byte
cache lines).
The existing ____cacheline_aligned annotation aligns to L1_CACHE_BYTES
which is not always sufficient for DMA alignment. For example, with
L1_CACHE_BYTES = 32 and ARCH_DMA_MINALIGN = 128
- irq_lines[0].ires at offset 128
- irq_lines[1].type at offset 192
both in same 128-byte DMA cacheline [128-256)
When the device writes to irq_lines[0].ires and the CPU concurrently
modifies one of irq_lines[1].type/disabled/masked/queued flags,
corruption can occur on non-cache-coherent platforms.
Fix by using __dma_from_device_group_begin()/end() annotations on the
DMA buffers. Drop ____cacheline_aligned - it's not required to isolate
request and response, and keeping them would increase the memory cost.
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Message-ID: <ba7e025a6c84aed012421468d83639e5dae982b0.1767601130.git.mst@redhat.com>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reorder struct virtio_vsock fields to place the DMA buffer (event_list)
last. This eliminates the padding from aligning the struct size on
ARCH_DMA_MINALIGN.
Message-ID: <ce44f61af415521e00ab7492aa16d3d19f00bd5e.1769632071.git.mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
The evts array contains 64 small (8-byte) input events that share
cachelines with each other. When CONFIG_DMA_API_DEBUG is enabled,
this can trigger warnings about overlapping DMA mappings within
the same cacheline.
Previous patch isolated the array in its own cachelines,
so the warnings are now spurious.
Use virtqueue_add_inbuf_cache_clean() to indicate that the CPU does not
write into these cache lines, suppressing these warnings.
Message-ID: <4c885b4046323f68cf5cadc7fbfb00216b11dd20.1767601130.git.mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
The data buffer in struct virtrng_info is used for DMA_FROM_DEVICE via
virtqueue_add_inbuf() and shares cachelines with the adjacent
CPU-written fields (data_avail, data_idx).
The device writing to the DMA buffer and the CPU writing to adjacent
fields could corrupt each other's data on non-cache-coherent platforms.
Add __dma_from_device_group_begin()/end() annotations to place these
in distinct cache lines.
Message-ID: <157a63b6324d1f1307ddd4faa3b62a8b90a79423.1767601130.git.mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Current struct virtio_scsi_event_node layout has two problems:
The event (DMA_FROM_DEVICE) and work (CPU-written via
INIT_WORK/queue_work) fields share a cacheline.
On non-cache-coherent platforms, CPU writes to work can
corrupt device-written event data.
If ARCH_DMA_MINALIGN is large enough, the 8 events in event_list share
cachelines, triggering CONFIG_DMA_API_DEBUG warnings.
Fix the corruption by moving event buffers to a separate array and
aligning using __dma_from_device_group_begin()/end().
Suppress the (now spurious) DMA debug warnings using
virtqueue_add_inbuf_cache_clean().
Message-ID: <8801aeef7576a155299f19b6887682dd3a272aba.1767601130.git.mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
On non-cache-coherent platforms, when a structure contains a buffer
used for DMA alongside fields that the CPU writes to, cacheline sharing
can cause data corruption.
The evts array is used for DMA_FROM_DEVICE operations via
virtqueue_add_inbuf(). The adjacent lock and ready fields are written
by the CPU during normal operation. If these share cachelines with evts,
CPU writes can corrupt DMA data.
Add __dma_from_device_group_begin()/end() annotations to ensure evts is
isolated in its own cachelines.
Message-ID: <cd328233198a76618809bb5cd9a6ddcaa603a8a1.1767601130.git.mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
The event_list array contains 8 small (4-byte) events that share
cachelines with each other. When CONFIG_DMA_API_DEBUG is enabled,
this can trigger warnings about overlapping DMA mappings within
the same cacheline.
The previous patch isolated event_list in its own cache lines
so the warnings are spurious.
Use virtqueue_add_inbuf_cache_clean() to indicate that the CPU does not
write into these fields, suppressing the warnings.
Reported-by: Cong Wang <xiyou.wangcong@gmail.com>
Message-ID: <4b5bf63a7ebb782d87f643466b3669df567c9fe1.1767601130.git.mst@redhat.com>
Acked-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
On non-cache-coherent platforms, when a structure contains a buffer
used for DMA alongside fields that the CPU writes to, cacheline sharing
can cause data corruption.
The event_list array is used for DMA_FROM_DEVICE operations via
virtqueue_add_inbuf(). The adjacent event_run and guest_cid fields are
written by the CPU while the buffer is available, so mapped for the
device. If these share cachelines with event_list, CPU writes can
corrupt DMA data.
Add __dma_from_device_group_begin()/end() annotations to ensure event_list
is isolated in its own cachelines.
Message-ID: <f19ebd74f70c91cab4b0178df78cf6a6e107a96b.1767601130.git.mst@redhat.com>
Acked-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Add virtqueue_add_inbuf_cache_clean() for passing DMA_ATTR_CPU_CACHE_CLEAN
to virtqueue operations. This suppresses DMA debug cacheline overlap
warnings for buffers where proper cache management is ensured by the
caller.
Message-ID: <e50d38c974859e731e50bda7a0ee5691debf5bc4.1767601130.git.mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
If a driver is buggy and has 2 overlapping mappings but only
sets cache clean flag on the 1st one of them, we warn.
But if it only does it for the 2nd one, we don't.
Fix by tracking cache clean flag in the entry.
Message-ID: <0ffb3513d18614539c108b4548cdfbc64274a7d1.1767601130.git.mst@redhat.com>
Reviewed-by: Petr Tesarik <ptesarik@suse.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Document DMA_ATTR_CPU_CACHE_CLEAN as implemented in the
previous patch.
Message-ID: <0720b4be31c1b7a38edca67fd0c97983d2a56936.1767601130.git.mst@redhat.com>
Reviewed-by: Petr Tesarik <ptesarik@suse.com>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
When multiple small DMA_FROM_DEVICE or DMA_BIDIRECTIONAL buffers share a
cacheline, and DMA_API_DEBUG is enabled, we get this warning:
cacheline tracking EEXIST, overlapping mappings aren't supported.
This is because when one of the mappings is removed, while another one
is active, CPU might write into the buffer.
Add an attribute for the driver to promise not to do this, making the
overlapping safe, and suppressing the warning.
Message-ID: <2d5d091f9d84b68ea96abd545b365dd1d00bbf48.1767601130.git.mst@redhat.com>
Reviewed-by: Petr Tesarik <ptesarik@suse.com>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Document the __dma_from_device_group_begin()/end() annotations.
Message-ID: <01ea88055ded4d70cac70ba557680fd5fa7d9ff5.1767601130.git.mst@redhat.com>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Petr Tesarik <ptesarik@suse.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
When a structure contains a buffer that DMA writes to alongside fields
that the CPU writes to, cache line sharing between the DMA buffer and
CPU-written fields can cause data corruption on non-cache-coherent
platforms.
Add __dma_from_device_group_begin()/end() annotations to ensure proper
alignment to prevent this:
struct my_device {
spinlock_t lock1;
__dma_from_device_group_begin();
char dma_buffer1[16];
char dma_buffer2[16];
__dma_from_device_group_end();
spinlock_t lock2;
};
Message-ID: <19163086d5e4704c316f18f6da06bc1c72968904.1767601130.git.mst@redhat.com>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Petr Tesarik <ptesarik@suse.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This patch implements in order support for both split virtqueue and
packed virtqueue. Performance could be gained for the device where the
memory access could be expensive (e.g vhost-net or a real PCI device):
Benchmark with KVM guest:
Vhost-net on the host: (pktgen + XDP_DROP):
in_order=off | in_order=on | +%
TX: 4.51Mpps | 5.30Mpps | +17%
RX: 3.47Mpps | 3.61Mpps | + 4%
Vhost-user(testpmd) on the host: (pktgen/XDP_DROP):
For split virtqueue:
in_order=off | in_order=on | +%
TX: 5.60Mpps | 5.60Mpps | +0.0%
RX: 9.16Mpps | 9.61Mpps | +4.9%
For packed virtqueue:
in_order=off | in_order=on | +%
TX: 5.60Mpps | 5.70Mpps | +1.7%
RX: 10.6Mpps | 10.8Mpps | +1.8%
Benchmark also shows no performance impact for in_order=off for queue
size with 256 and 1024.
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-20-jasowang@redhat.com>
This patch factors out the split core detaching logic that could be
reused by in order feature into a dedicated function.
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-19-jasowang@redhat.com>
Factor out the split indirect descriptor detaching logic in order to
allow it to be reused by the in order support.
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-18-jasowang@redhat.com>
Factor out the core logic for updating last_used_idx to be reused by
the packed in order implementation.
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-17-jasowang@redhat.com>
Factor out core logic of buffer detaching and leave the free list
management to the caller so in_order can just call the core logic.
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-16-jasowang@redhat.com>
Let's determine the last descriptor by counting the number of sg. This
would be consistent with packed virtqueue implementation and ease the
future in-order implementation.
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-15-jasowang@redhat.com>
This patch introduces virtqueue ops which is a set of callbacks
that will be called for different queue layout or features. This would
help to avoid branches for split/packed and will ease the future
implementation like in order.
Note that in order to eliminate the indirect calls this patch uses
global array of const ops to allow compiler to avoid indirect
branches.
Tested with CONFIG_MITIGATION_RETPOLINE, no performance differences
were noticed.
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-14-jasowang@redhat.com>
Switch to use unsigned int for virtqueue_poll_packed() to match
virtqueue_poll() and virtqueue_poll_split() and to ease the
abstraction of the virtqueue ops.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-13-jasowang@redhat.com>
Those variants are used internally so let's switch to use
vring_virtqueue as parameter to be consistent with other internal
virtqueue helpers.
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-12-jasowang@redhat.com>
Those variants are used internally so let's switch to use
vring_virtqueue as parameter to be consistent with other internal
virtqueue helpers.
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-11-jasowang@redhat.com>
Those variants are used internally so let's switch to use
vring_virtqueue as parameter to be consistent with other internal
virtqueue helpers.
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-10-jasowang@redhat.com>
Those variants are used internally so let's switch to use
vring_virtqueue as parameter to be consistent with other internal
virtqueue helpers.
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-9-jasowang@redhat.com>
Those variants are used internally so let's switch to use
vring_virtqueue as parameter to be consistent with other internal
virtqueue helpers.
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-8-jasowang@redhat.com>
Those variants are used internally so let's switch to use
vring_virtqueue as parameter to be consistent with other internal
virtqueue helpers.
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-7-jasowang@redhat.com>
Those variants are used internally so let's switch to use
vring_virtqueue as parameter to be consistent with other internal
virtqueue helpers.
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-6-jasowang@redhat.com>
Those variants are used internally so let's switch to use
vring_virtqueue as parameter to be consistent with other internal
virtqueue helpers.
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-5-jasowang@redhat.com>
This patch unifies the logic of virtqueue_poll() and more_used() for
better code reusing and ease the future in order implementation.
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-4-jasowang@redhat.com>
Those variants are used internally so let's switch to use
vring_virtqueue as parameter to be consistent with other internal
virtqueue helpers.
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-3-jasowang@redhat.com>
To be consistent with virtqueue_reset().
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20251230064649.55597-2-jasowang@redhat.com>
vhost_get_user and vhost_put_user leverage __get_user and __put_user,
respectively, which were both added in 2016 by commit 6b1e6cc785
("vhost: new device IOTLB API"). In a heavy UDP transmit workload on a
vhost-net backed tap device, these functions showed up as ~11.6% of
samples in a flamegraph of the underlying vhost worker thread.
Quoting Linus from [1]:
Anyway, every single __get_user() call I looked at looked like
historical garbage. [...] End result: I get the feeling that we
should just do a global search-and-replace of the __get_user/
__put_user users, replace them with plain get_user/put_user instead,
and then fix up any fallout (eg the coco code).
Switch to plain get_user/put_user in vhost, which results in a slight
throughput speedup. get_user now about ~8.4% of samples in flamegraph.
Basic iperf3 test on a Intel 5416S CPU with Ubuntu 25.10 guest:
TX: taskset -c 2 iperf3 -c <rx_ip> -t 60 -p 5200 -b 0 -u -i 5
RX: taskset -c 2 iperf3 -s -p 5200 -D
Before: 6.08 Gbits/sec
After: 6.32 Gbits/sec
As to what drives the speedup, Sean's patch [2] explains:
Use the normal, checked versions for get_user() and put_user() instead of
the double-underscore versions that omit range checks, as the checked
versions are actually measurably faster on modern CPUs (12%+ on Intel,
25%+ on AMD).
The performance hit on the unchecked versions is almost entirely due to
the added LFENCE on CPUs where LFENCE is serializing (which is effectively
all modern CPUs), which was added by commit 304ec1b050 ("x86/uaccess:
Use __uaccess_begin_nospec() and uaccess_try_nospec"). The small
optimizations done by commit b19b74bc99 ("x86/mm: Rework address range
check in get_user() and put_user()") likely shave a few cycles off, but
the bulk of the extra latency comes from the LFENCE.
[1] https://lore.kernel.org/all/CAHk-=wiJiDSPZJTV7z3Q-u4DfLgQTNWqUqqrwSBHp0+Dh016FA@mail.gmail.com/
[2] https://lore.kernel.org/all/20251106210206.221558-1-seanjc@google.com/
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Sean Christopherson <seanjc@google.com>
Signed-off-by: Jon Kohler <jon@nutanix.com>
Message-Id: <20251113005529.2494066-1-jon@nutanix.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Since the return value of vring_unmap_one_split() is exactly
vq->split.desc_extra[i].next, 'i = vq->split.desc_extra[i].next' is
redundant. Assign vring_unmap_one_split() to i instead.
Since vq->split.desc_extra is assigned to extra, use extra[i].next
instead of vq->split.desc_extra[i].next to improve readability.
No change in functionality.
Signed-off-by: zhangdongchuan <zhangdongchuan@eswincomputing.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <202511261140162936986@eswincomputing.com>
