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Re: [RFC PATCH] hw/virtio: Do not access vring cache if queue is not rea
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From: |
Stefan Hajnoczi |
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Subject: |
Re: [RFC PATCH] hw/virtio: Do not access vring cache if queue is not ready |
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Date: |
Thu, 26 Aug 2021 08:45:48 +0100 |
On Thu, Aug 26, 2021 at 12:50:34AM +0200, Philippe Mathieu-Daudé wrote:
> On 8/25/21 10:36 PM, Philippe Mathieu-Daudé wrote:
> > On 8/25/21 10:09 PM, Philippe Mathieu-Daudé wrote:
> >> Do not intent to access the vring MemoryRegion cache if
> >> the queue is not ready (no vring available).
> >>
> >> This fixes issue #301:
> >>
> >> qemu-system-i386: include/exec/memory_ldst_cached.h.inc:77: void
> >> address_space_stw_le_cached(MemoryRegionCache *, hwaddr, uint16_t,
> >> MemTxAttrs, MemTxResult *):
> >> Assertion `addr < cache->len && 2 <= cache->len - addr' failed.
> >> Thread 1 "qemu-system-i38" received signal SIGABRT, Aborted.
> >> (gdb) bt
> >> #1 0x00007ffff4d1a8a4 in abort () at /lib64/libc.so.6
> >> #4 0x0000555558f2a122 in address_space_stw_le_cached
> >> (cache=0x61300010bb70, addr=516, val=0, attrs=..., result=0x0) at
> >> include/exec/memory_ldst_cached.h.inc:77
> >> #5 0x0000555558f2964c in stw_le_phys_cached (cache=0x61300010bb70,
> >> addr=516, val=0) at include/exec/memory_ldst_phys.h.inc:109
> >> #6 0x0000555558f28da8 in virtio_stw_phys_cached (vdev=0x62d00004e680,
> >> cache=0x61300010bb70, pa=516, value=0) at
> >> include/hw/virtio/virtio-access.h:196
> >> #7 0x0000555558f287dc in vring_set_avail_event (vq=0x7fff5d23e800,
> >> val=0) at hw/virtio/virtio.c:428
> >> #8 0x0000555558efabb7 in virtio_queue_split_set_notification
> >> (vq=0x7fff5d23e800, enable=1) at hw/virtio/virtio.c:437
> >> #9 0x0000555558ef9f3c in virtio_queue_set_notification
> >> (vq=0x7fff5d23e800, enable=1) at hw/virtio/virtio.c:498
> >> #10 0x0000555558c94786 in virtio_blk_handle_vq (s=0x62d00004e680,
> >> vq=0x7fff5d23e800) at hw/block/virtio-blk.c:795
> >> #11 0x0000555558cb96c2 in virtio_blk_data_plane_handle_output
> >> (vdev=0x62d00004e680, vq=0x7fff5d23e800) at
> >> hw/block/dataplane/virtio-blk.c:165
> >> #12 0x0000555558f35937 in virtio_queue_notify_aio_vq (vq=0x7fff5d23e800)
> >> at hw/virtio/virtio.c:2323
> >> #13 0x0000555558f264b3 in virtio_queue_host_notifier_aio_read
> >> (n=0x7fff5d23e87c) at hw/virtio/virtio.c:3532
> >> #14 0x0000555559a9cd3e in aio_dispatch_handler (ctx=0x613000063000,
> >> node=0x60d000008f40) at util/aio-posix.c:329
> >> #15 0x0000555559a963ae in aio_dispatch_handlers (ctx=0x613000063000) at
> >> util/aio-posix.c:372
> >> #16 0x0000555559a95f82 in aio_dispatch (ctx=0x613000063000) at
> >> util/aio-posix.c:382
> >>
> >> and #302:
> >>
> >> 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: Cheolwoo Myung <cwmyung@snu.ac.kr>
> >> Reported-by: Qiuhao Li <Qiuhao.Li@outlook.com>
> >> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/301
> >> BugLink: https://bugs.launchpad.net/qemu/+bug/1910941
> >> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/302
> >> BugLink: https://bugs.launchpad.net/qemu/+bug/1913510
> >> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> >> ---
> >> Could be more readable to use virtio_queue_ready()
> >>
> >> RFC because I have no clue about this hot path code,
> >> I simply looked at the backtraces.
> >> ---
> >> hw/virtio/virtio.c | 82 +++++++++++++++++++++++++++++++++++++---------
> >> 1 file changed, 66 insertions(+), 16 deletions(-)
> >>
> >> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> >> index 874377f37a7..be1ec9e05ef 100644
> >> --- a/hw/virtio/virtio.c
> >> +++ b/hw/virtio/virtio.c
> >> @@ -289,26 +289,38 @@ static VRingMemoryRegionCaches
> >> *vring_get_region_caches(struct VirtQueue *vq)
> >> /* Called within rcu_read_lock(). */
> >> static inline uint16_t vring_avail_flags(VirtQueue *vq)
> >> {
> >> - VRingMemoryRegionCaches *caches = vring_get_region_caches(vq);
> >> - hwaddr pa = offsetof(VRingAvail, flags);
> >> + VRingMemoryRegionCaches *caches;
> >> + hwaddr pa;
> >>
> >> + if (unlikely(!vq->vring.avail)) {
> >> + return 0;
> >> + }
> >> +
> >> + caches = vring_get_region_caches(vq);
> >> if (!caches) {
> >> return 0;
> >> }
> >>
> >> + pa = offsetof(VRingAvail, flags);
> >> return virtio_lduw_phys_cached(vq->vdev, &caches->avail, pa);
> >> }
> >>
> >> /* Called within rcu_read_lock(). */
> >> static inline uint16_t vring_avail_idx(VirtQueue *vq)
> >> {
> >> - VRingMemoryRegionCaches *caches = vring_get_region_caches(vq);
> >> - hwaddr pa = offsetof(VRingAvail, idx);
> >> + VRingMemoryRegionCaches *caches;
> >> + hwaddr pa;
> >>
> >> + if (unlikely(!vq->vring.avail)) {
> >> + return 0;
> >> + }
> >> +
> >> + caches = vring_get_region_caches(vq);
> >> if (!caches) {
> >> return 0;
> >> }
> >>
> >> + pa = offsetof(VRingAvail, idx);
> >> vq->shadow_avail_idx = virtio_lduw_phys_cached(vq->vdev,
> >> &caches->avail, pa);
> >> return vq->shadow_avail_idx;
> >> }
> >> @@ -316,13 +328,19 @@ static inline uint16_t vring_avail_idx(VirtQueue *vq)
> >> /* Called within rcu_read_lock(). */
> >> static inline uint16_t vring_avail_ring(VirtQueue *vq, int i)
> >> {
> >> - VRingMemoryRegionCaches *caches = vring_get_region_caches(vq);
> >> - hwaddr pa = offsetof(VRingAvail, ring[i]);
> >> + VRingMemoryRegionCaches *caches;
> >> + hwaddr pa;
> >>
> >> + if (unlikely(!vq->vring.avail)) {
> >> + return 0;
> >> + }
> >> +
> >> + caches = vring_get_region_caches(vq);
> >> if (!caches) {
> >> return 0;
> >> }
> >>
> >> + pa = offsetof(VRingAvail, ring[i]);
> >> return virtio_lduw_phys_cached(vq->vdev, &caches->avail, pa);
> >> }
> >
> > Self-NAck.
> >
> > While the previous part could be OK, what follows is crap (checking
> > avail instead of used) so please disregard this patch.
>
> Previous part is also crap :/
The topic reminds me of:
commit abdd16f4681cc4d6bf84990227b5c9b98e869ccd
Author: Stefan Hajnoczi <stefanha@redhat.com>
Date: Fri Feb 7 10:46:19 2020 +0000
virtio: gracefully handle invalid region caches
Stefan
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