[PATCH] hw/virtio: Update vring after modifying its queue size

[Philippe Mathieu-Daudé]

When a ring queue size is modified, we need to call
virtio_queue_update_rings() to re-init the memory region
caches. Otherwise the region might have outdated memory
size, and later load/store access might trigger an
assertion, such:

  qemu-system-i386: include/exec/memory_ldst_cached.h.inc:30: uint16_t 
address_space_lduw_le_cached(MemoryRegionCache *, hwaddr, MemTxAttrs, 
MemTxResult *):
  Assertion `addr < cache->len && 2 <= cache->len - addr' failed.
  Thread 1 "qemu-system-i38" received signal SIGABRT, Aborted.
  0x00007ffff4d312a2 in raise () from /lib64/libc.so.6
  (gdb) bt
  #1  0x00007ffff4d1a8a4 in abort () at /lib64/libc.so.6
  #4  0x0000555558f2b8ec in address_space_lduw_le_cached (cache=0x61300010a7c0, 
addr=134, attrs=..., result=0x0) at include/exec/memory_ldst_cached.h.inc:30
  #5  0x0000555558f2ac6b in lduw_le_phys_cached (cache=0x61300010a7c0, 
addr=134) at include/exec/memory_ldst_phys.h.inc:67
  #6  0x0000555558f2a3cd in virtio_lduw_phys_cached (vdev=0x62d00003a680, 
cache=0x61300010a7c0, pa=134) at include/hw/virtio/virtio-access.h:166
  #7  0x0000555558f300ea in vring_avail_ring (vq=0x7fffdd55d8a0, i=65) at 
hw/virtio/virtio.c:326
  #8  0x0000555558f33b10 in vring_get_used_event (vq=0x7fffdd55d8a0) at 
hw/virtio/virtio.c:332
  #9  0x0000555558f33677 in virtio_split_should_notify (vdev=0x62d00003a680, 
vq=0x7fffdd55d8a0) at hw/virtio/virtio.c:2471
  #10 0x0000555558f1859f in virtio_should_notify (vdev=0x62d00003a680, 
vq=0x7fffdd55d8a0) at hw/virtio/virtio.c:2523
  #11 0x0000555558f188cc in virtio_notify (vdev=0x62d00003a680, 
vq=0x7fffdd55d8a0) at hw/virtio/virtio.c:2565
  #12 0x0000555557c2bd52 in virtio_input_handle_sts (vdev=0x62d00003a680, 
vq=0x7fffdd55d8a0) at hw/input/virtio-input.c:100
  #13 0x0000555558f16df7 in virtio_queue_notify (vdev=0x62d00003a680, n=1) at 
hw/virtio/virtio.c:2363
  #14 0x00005555583f45c0 in virtio_pci_notify_write (opaque=0x62d000032400, 
addr=7, val=0, size=1) at hw/virtio/virtio-pci.c:1369
  #15 0x0000555558b80b04 in memory_region_write_accessor (mr=0x62d000033190, 
addr=7, value=0x7fffffff8eb0, size=1, shift=0, mask=255, attrs=...) at 
softmmu/memory.c:492

Reported-by: Qiuhao Li <qiuhao...@outlook.com>
Fixes: ab223c9518e ("virtio: allow virtio-1 queue layout")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/302
BugLink: https://bugs.launchpad.net/qemu/+bug/1913510
Signed-off-by: Philippe Mathieu-Daudé <phi...@redhat.com>
---
 hw/virtio/virtio.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 874377f37a7..04ffe5f420e 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2255,6 +2255,7 @@ void virtio_queue_set_num(VirtIODevice *vdev, int n, int 
num)
         return;
     }
     vdev->vq[n].vring.num = num;
+    virtio_queue_update_rings(vdev, n);
 }
 
 VirtQueue *virtio_vector_first_queue(VirtIODevice *vdev, uint16_t vector)
-- 
2.31.1