| 61b6d9b7 | 07-Apr-2025 |
Kevin Wolf <kwolf@redhat.com> |
scsi-disk: Apply error policy for host_status errors again
Originally, all failed SG_IO requests called scsi_handle_rw_error() to
apply the configured error policy. However, commit f3126d65, which w
scsi-disk: Apply error policy for host_status errors again
Originally, all failed SG_IO requests called scsi_handle_rw_error() to
apply the configured error policy. However, commit f3126d65, which was
supposed to be a mere refactoring for scsi-disk.c, broke this and
accidentally completed the SCSI request without considering the error
policy any more if the error was signalled in the host_status field.
Apart from the commit message not describing the change as intended,
errors indicated in host_status are also obviously backend errors and
not something the guest must deal with independently of the error
policy.
This behaviour means that some recoverable errors (such as a path error
in multipath configurations) were reported to the guest anyway, which
might not expect it and might consider its disk broken.
Make sure that we apply the error policy again for host_status errors,
too. This addresses an existing FIXME comment and allows us to remove
some comments warning that callbacks weren't always called. With this
fix, they are called in all cases again.
The return value passed to the request callback doesn't have more free
values that could be used to indicate host_status errors as well as SAM
status codes and negative errno. Store the value in the host_status
field of the SCSIRequest instead and use -ENODEV as the return value (if
a path hasn't been reachable for a while, blk_aio_ioctl() will return
-ENODEV instead of just setting host_status, so just reuse it here -
it's not necessarily entirely accurate, but it's as good as any errno).
Cc: qemu-stable@nongnu.org
Fixes: f3126d65b393 ('scsi: move host_status handling into SCSI drivers')
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20250407155949.44736-1-kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
show more ...
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| 40aa38a6 | 11-Mar-2025 |
Stefan Hajnoczi <stefanha@redhat.com> |
virtio-scsi: only expose cmd vqs via iothread-vq-mapping
Peter Krempa and Kevin Wolf observed that iothread-vq-mapping is
confusing to use because the control and event virtqueues have a fixed
locat
virtio-scsi: only expose cmd vqs via iothread-vq-mapping
Peter Krempa and Kevin Wolf observed that iothread-vq-mapping is
confusing to use because the control and event virtqueues have a fixed
location before the command virtqueues but need to be treated
differently.
Only expose the command virtqueues via iothread-vq-mapping so that the
command-line parameter is intuitive: it controls where SCSI requests are
processed.
The control virtqueue needs to be hardcoded to the main loop thread for
technical reasons anyway. Kevin also pointed out that it's better to
place the event virtqueue in the main loop thread since its no poll
behavior would prevent polling if assigned to an IOThread.
This change is its own commit to avoid squashing the previous commit.
Suggested-by: Kevin Wolf <kwolf@redhat.com>
Suggested-by: Peter Krempa <pkrempa@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20250311132616.1049687-14-stefanha@redhat.com>
Tested-by: Peter Krempa <pkrempa@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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| bcede51d | 11-Mar-2025 |
Stefan Hajnoczi <stefanha@redhat.com> |
virtio-scsi: handle ctrl virtqueue in main loop
Previously the ctrl virtqueue was handled in the AioContext where SCSI
requests are processed. When IOThread Virtqueue Mapping was added things
become
virtio-scsi: handle ctrl virtqueue in main loop
Previously the ctrl virtqueue was handled in the AioContext where SCSI
requests are processed. When IOThread Virtqueue Mapping was added things
become more complicated because SCSI requests could run in other
AioContexts.
Simplify by handling the ctrl virtqueue in the main loop where reset
operations can be performed. Note that BHs are still used canceling SCSI
requests in their AioContexts but at least the mean loop activity
doesn't need BHs anymore.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20250311132616.1049687-13-stefanha@redhat.com>
Tested-by: Peter Krempa <pkrempa@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
show more ...
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| 2e8e18c2 | 11-Mar-2025 |
Stefan Hajnoczi <stefanha@redhat.com> |
virtio-scsi: add iothread-vq-mapping parameter
Allow virtio-scsi virtqueues to be assigned to different IOThreads. This
makes it possible to take advantage of host multi-queue block layer
scalabilit
virtio-scsi: add iothread-vq-mapping parameter
Allow virtio-scsi virtqueues to be assigned to different IOThreads. This
makes it possible to take advantage of host multi-queue block layer
scalability by assigning virtqueues that have affinity with vCPUs to
different IOThreads that have affinity with host CPUs. The same feature
was introduced for virtio-blk in the past:
https://developers.redhat.com/articles/2024/09/05/scaling-virtio-blk-disk-io-iothread-virtqueue-mapping
Here are fio randread 4k iodepth=64 results from a 4 vCPU guest with an
Intel P4800X SSD:
iothreads IOPS
------------------------------
1 189576
2 312698
4 346744
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20250311132616.1049687-12-stefanha@redhat.com>
Tested-by: Peter Krempa <pkrempa@redhat.com>
[kwolf: Updated 051 output, virtio-scsi can now use any iothread]
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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| da6eebb3 | 11-Mar-2025 |
Stefan Hajnoczi <stefanha@redhat.com> |
virtio-scsi: perform TMFs in appropriate AioContexts
With IOThread Virtqueue Mapping there will be multiple AioContexts
processing SCSI requests. scsi_req_cancel() and other SCSI request
operations
virtio-scsi: perform TMFs in appropriate AioContexts
With IOThread Virtqueue Mapping there will be multiple AioContexts
processing SCSI requests. scsi_req_cancel() and other SCSI request
operations must be performed from the AioContext where the request is
running.
Introduce a virtio_scsi_defer_tmf_to_aio_context() function and the
necessary VirtIOSCSIReq->remaining refcount infrastructure to move the
TMF code into the AioContext where the request is running.
For the time being there is still just one AioContext: the main loop or
the IOThread. When the iothread-vq-mapping parameter is added in a later
patch this will be changed to per-virtqueue AioContexts.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20250311132616.1049687-8-stefanha@redhat.com>
Tested-by: Peter Krempa <pkrempa@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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| 7d8ab5b2 | 11-Mar-2025 |
Stefan Hajnoczi <stefanha@redhat.com> |
virtio-scsi: protect events_dropped field
The block layer can invoke the resize callback from any AioContext that
is processing requests. The virtqueue is already protected but the
events_dropped fi
virtio-scsi: protect events_dropped field
The block layer can invoke the resize callback from any AioContext that
is processing requests. The virtqueue is already protected but the
events_dropped field also needs to be protected against races. Cover it
using the event virtqueue lock because it is closely associated with
accesses to the virtqueue.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20250311132616.1049687-7-stefanha@redhat.com>
Tested-by: Peter Krempa <pkrempa@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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| b348ca2e | 11-Mar-2025 |
Stefan Hajnoczi <stefanha@redhat.com> |
virtio-scsi: introduce event and ctrl virtqueue locks
Virtqueues are not thread-safe. Until now this was not a major issue
since all virtqueue processing happened in the same thread. The ctrl
queue'
virtio-scsi: introduce event and ctrl virtqueue locks
Virtqueues are not thread-safe. Until now this was not a major issue
since all virtqueue processing happened in the same thread. The ctrl
queue's Task Management Function (TMF) requests sometimes need the main
loop, so a BH was used to schedule the virtqueue completion back in the
thread that has virtqueue access.
When IOThread Virtqueue Mapping is introduced in later commits, event
and ctrl virtqueue accesses from other threads will become necessary.
Introduce an optional per-virtqueue lock so the event and ctrl
virtqueues can be protected in the commits that follow.
The addition of the ctrl virtqueue lock makes
virtio_scsi_complete_req_from_main_loop() and its BH unnecessary.
Instead, take the ctrl virtqueue lock from the main loop thread.
The cmd virtqueue does not have a lock because the entirety of SCSI
command processing happens in one thread. Only one thread accesses the
cmd virtqueue and a lock is unnecessary.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20250311132616.1049687-6-stefanha@redhat.com>
Tested-by: Peter Krempa <pkrempa@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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| 1cf18cc9 | 11-Mar-2025 |
Stefan Hajnoczi <stefanha@redhat.com> |
scsi: introduce requests_lock
SCSIDevice keeps track of in-flight requests for device reset and Task
Management Functions (TMFs). The request list requires protection so
that multi-threaded SCSI emu
scsi: introduce requests_lock
SCSIDevice keeps track of in-flight requests for device reset and Task
Management Functions (TMFs). The request list requires protection so
that multi-threaded SCSI emulation can be implemented in commits that
follow.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20250311132616.1049687-5-stefanha@redhat.com>
Tested-by: Peter Krempa <pkrempa@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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| 7eecba37 | 11-Mar-2025 |
Stefan Hajnoczi <stefanha@redhat.com> |
scsi: track per-SCSIRequest AioContext
Until now, a SCSIDevice's I/O requests have run in a single AioContext.
In order to support multiple IOThreads it will be necessary to move to
the concept of a
scsi: track per-SCSIRequest AioContext
Until now, a SCSIDevice's I/O requests have run in a single AioContext.
In order to support multiple IOThreads it will be necessary to move to
the concept of a per-SCSIRequest AioContext.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20250311132616.1049687-4-stefanha@redhat.com>
Tested-by: Peter Krempa <pkrempa@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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| a89c3c9b | 11-Mar-2025 |
Stefan Hajnoczi <stefanha@redhat.com> |
dma: use current AioContext for dma_blk_io()
In the past a single AioContext was used for block I/O and it was
fetched using blk_get_aio_context(). Nowadays the block layer supports
running I/O from
dma: use current AioContext for dma_blk_io()
In the past a single AioContext was used for block I/O and it was
fetched using blk_get_aio_context(). Nowadays the block layer supports
running I/O from any AioContext and multiple AioContexts at the same
time. Remove the dma_blk_io() AioContext argument and use the current
AioContext instead.
This makes calling the function easier and enables multiple IOThreads to
use dma_blk_io() concurrently for the same block device.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20250311132616.1049687-3-stefanha@redhat.com>
Tested-by: Peter Krempa <pkrempa@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
show more ...
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