From: Stefan Hajnoczi <stefanha@redhat.com>
To: "Philippe Mathieu-Daudé" <philmd@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>,
"Michael S. Tsirkin" <mst@redhat.com>,
Richard Henderson <richard.henderson@linaro.org>,
qemu-devel@nongnu.org, Peter Xu <peterx@redhat.com>,
Bibo Mao <maobibo@loongson.cn>,
Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [RFC PATCH 12/12] hw/virtio: Display error if vring flag field is not aligned
Date: Wed, 2 Jun 2021 13:44:13 +0100 [thread overview]
Message-ID: <YLd9Hb34kEU8wLN0@stefanha-x1.localdomain> (raw)
In-Reply-To: <20210520110919.2483190-13-philmd@redhat.com>
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On Thu, May 20, 2021 at 01:09:19PM +0200, Philippe Mathieu-Daudé wrote:
> {
> VRingMemoryRegionCaches *caches = vring_get_region_caches(vq);
> hwaddr pa = offsetof(VRingAvail, flags);
> + MemTxAttrs attrs = { .aligned = 1 };
> + MemTxResult res;
>
> if (!caches) {
> *val = 0;
> return true;
> }
>
> - *val = virtio_lduw_phys_cached_with_attrs(vq->vdev, &caches->avail, pa);
> + *val = virtio_lduw_phys_cached_with_attrs(vq->vdev, &caches->avail,
> + pa, attrs, &res);
> + if (res == MEMTX_UNALIGNED_ERROR) {
> + qemu_log_mask(LOG_GUEST_ERROR,
> + "virtio: vring flag address 0x%" HWADDR_PRIX " "
> + "is not aligned\n", pa);
> + return false;
> + }
Performance-critical code paths could validate the cache and offset
ahead of time to avoid taking the more expensive code path that checks
MemTxAttrs.
The guest driver configures the vring addresses by writing to
virtio-pci/virtio-mmio registers. The alignment check can be performed
at that time (while/before creating the cache).
Stefan
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next prev parent reply other threads:[~2021-06-02 12:45 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-20 11:09 [RFC PATCH 00/12] exec/memory: Experimental API to catch unaligned accesses Philippe Mathieu-Daudé
2021-05-20 11:09 ` [RFC PATCH 01/12] exec/memory_ldst: Use correct type sizes Philippe Mathieu-Daudé
2021-05-20 11:09 ` [RFC PATCH 02/12] exec/memattrs: Add attribute/error for address alignment Philippe Mathieu-Daudé
2021-06-02 12:39 ` Stefan Hajnoczi
2021-05-20 11:09 ` [RFC PATCH 03/12] exec/memory_ldst: Return MEMTX_UNALIGNED_ERROR for unaligned addresses Philippe Mathieu-Daudé
2021-05-20 11:09 ` [RFC PATCH 04/12] exec/memory_ldst_cached: Sort declarations Philippe Mathieu-Daudé
2021-05-20 11:09 ` [RFC PATCH 05/12] exec/memory_ldst_cached: Use correct type size Philippe Mathieu-Daudé
2021-05-20 11:09 ` [RFC PATCH 06/12] exec/memory_ldst_cached: Set MemTxResult on success Philippe Mathieu-Daudé
2021-05-20 11:09 ` [RFC PATCH 07/12] exec/memory_ldst_cached: Document aligned addresses are expected Philippe Mathieu-Daudé
2021-05-20 11:09 ` [RFC PATCH 08/12] exec/memory_ldst_cached: Check address alignment if requested Philippe Mathieu-Daudé
2021-05-20 11:09 ` [RFC PATCH 09/12] hw/virtio: Use correct type sizes Philippe Mathieu-Daudé
2021-05-20 11:09 ` [RFC PATCH 10/12] hw/virtio: Extract virtio_lduw_phys_cached_with_attrs() Philippe Mathieu-Daudé
2021-05-20 11:09 ` [RFC PATCH 11/12] hw/virtio: Have vring_avail_flags() return a boolean value Philippe Mathieu-Daudé
2021-05-20 11:09 ` [RFC PATCH 12/12] hw/virtio: Display error if vring flag field is not aligned Philippe Mathieu-Daudé
2021-06-02 12:44 ` Stefan Hajnoczi [this message]
2021-06-01 3:32 ` [RFC PATCH 00/12] exec/memory: Experimental API to catch unaligned accesses Philippe Mathieu-Daudé
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