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Re: [RFC PATCH] hw/virtio: Do not access vring cache if queue is not rea
From: |
Philippe Mathieu-Daudé |
Subject: |
Re: [RFC PATCH] hw/virtio: Do not access vring cache if queue is not ready |
Date: |
Thu, 26 Aug 2021 00:50:34 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 |
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 :/