github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-12 16:18:45 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity

virtio_scsi: fix DMA cacheline issues for events

Browse Source 
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>
This commit is contained in:
Michael S. Tsirkin 2025-12-29 18:25:16 -05:00
parent 95c7b0ad6c
commit 2678369e8e
1 changed files with 12 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
drivers/scsi/virtio_scsi.c
View File

@ -29,6 +29,7 @@
#include <scsi/scsi_tcq.h>
#include <scsi/scsi_devinfo.h>
#include <linux/seqlock.h>
#include <linux/dma-mapping.h>
#include "sd.h"
@ -61,7 +62,7 @@ struct virtio_scsi_cmd {
struct virtio_scsi_event_node {
struct virtio_scsi *vscsi;
struct virtio_scsi_event event;
struct virtio_scsi_event *event;
struct work_struct work;
};
@ -89,6 +90,11 @@ struct virtio_scsi {
struct virtio_scsi_vq ctrl_vq;
struct virtio_scsi_vq event_vq;
__dma_from_device_group_begin();
struct virtio_scsi_event events[VIRTIO_SCSI_EVENT_LEN];
__dma_from_device_group_end();
struct virtio_scsi_vq req_vqs[];
};
@ -237,12 +243,12 @@ static int virtscsi_kick_event(struct virtio_scsi *vscsi,
unsigned long flags;
INIT_WORK(&event_node->work, virtscsi_handle_event);
sg_init_one(&sg, &event_node->event, sizeof(struct virtio_scsi_event));
sg_init_one(&sg, event_node->event, sizeof(struct virtio_scsi_event));
spin_lock_irqsave(&vscsi->event_vq.vq_lock, flags);
err = virtqueue_add_inbuf(vscsi->event_vq.vq, &sg, 1, event_node,
GFP_ATOMIC);
err = virtqueue_add_inbuf_cache_clean(vscsi->event_vq.vq, &sg, 1, event_node,
GFP_ATOMIC);
if (!err)
virtqueue_kick(vscsi->event_vq.vq);
@ -257,6 +263,7 @@ static int virtscsi_kick_event_all(struct virtio_scsi *vscsi)
for (i = 0; i < VIRTIO_SCSI_EVENT_LEN; i++) {
vscsi->event_list[i].vscsi = vscsi;
vscsi->event_list[i].event = &vscsi->events[i];
virtscsi_kick_event(vscsi, &vscsi->event_list[i]);
}
@ -380,7 +387,7 @@ static void virtscsi_handle_event(struct work_struct *work)
struct virtio_scsi_event_node *event_node =
container_of(work, struct virtio_scsi_event_node, work);
struct virtio_scsi *vscsi = event_node->vscsi;
struct virtio_scsi_event *event = &event_node->event;
struct virtio_scsi_event *event = event_node->event;
if (event->event &
cpu_to_virtio32(vscsi->vdev, VIRTIO_SCSI_T_EVENTS_MISSED)) {