Messages in this thread | | | Date | Tue, 4 Jul 2023 08:18:17 +0800 | Subject | PING Re: [PATCH] virtio_ring: use u32 for virtio_max_dma_size | From | zhenwei pi <> |
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Hi Michael,
This seems to be ignored...
On 5/10/23 12:06, Michael S. Tsirkin wrote: > On Wed, May 10, 2023 at 12:04:50PM +0800, Jason Wang wrote: >> On Wed, May 10, 2023 at 11:44 AM Michael S. Tsirkin <mst@redhat.com> wrote: >>> >>> On Wed, May 10, 2023 at 11:26:54AM +0800, Xuan Zhuo wrote: >>>> On Wed, 10 May 2023 10:54:37 +0800, zhenwei pi <pizhenwei@bytedance.com> wrote: >>>>> Both split ring and packed ring use 32bits to describe the length of >>>>> a descriptor: see struct vring_desc and struct vring_packed_desc. >>>>> This means the max segment size supported by virtio is U32_MAX. >>>>> >>>>> An example of virtio_max_dma_size in virtio_blk.c: >>>>> u32 v, max_size; >>>>> >>>>> max_size = virtio_max_dma_size(vdev); -> implicit convert >>>>> err = virtio_cread_feature(vdev, VIRTIO_BLK_F_SIZE_MAX, >>>>> struct virtio_blk_config, size_max, &v); >>>>> max_size = min(max_size, v); >>>>> >>>>> There is a risk during implicit convert here, once virtio_max_dma_size >>>>> returns 4G, max_size becomes 0. >>>>> >>>>> Fixes: e6d6dd6c875e ("virtio: Introduce virtio_max_dma_size()") >>>>> Cc: Joerg Roedel <jroedel@suse.de> >>>>> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com> >>>>> --- >>>>> drivers/virtio/virtio_ring.c | 12 ++++++++---- >>>>> include/linux/virtio.h | 2 +- >>>>> 2 files changed, 9 insertions(+), 5 deletions(-) >>>>> >>>>> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c >>>>> index c5310eaf8b46..55cfecf030a1 100644 >>>>> --- a/drivers/virtio/virtio_ring.c >>>>> +++ b/drivers/virtio/virtio_ring.c >>>>> @@ -289,12 +289,16 @@ static bool vring_use_dma_api(const struct virtio_device *vdev) >>>>> return false; >>>>> } >>>>> >>>>> -size_t virtio_max_dma_size(const struct virtio_device *vdev) >>>>> +u32 virtio_max_dma_size(const struct virtio_device *vdev) >>>> >>>> >>>> LGTM >>>> >>>> But, should we change the parameter to vq, then use the dma_dev? >>>> >>>> @Jason >>>> >>>> Thanks. >>>> >>> >>> >>> that would be an unrelated rework. >> >> Probably, but I think it's better to be done on top otherwise we may forget. >> >> Thanks > > Just to make things clear I'm merging fixes for this > release but cleanups belong in the next one. > >>> >>>>> { >>>>> - size_t max_segment_size = SIZE_MAX; >>>>> + u32 max_segment_size = U32_MAX; >>>>> >>>>> - if (vring_use_dma_api(vdev)) >>>>> - max_segment_size = dma_max_mapping_size(vdev->dev.parent); >>>>> + if (vring_use_dma_api(vdev)) { >>>>> + size_t max_dma_size = dma_max_mapping_size(vdev->dev.parent); >>>>> + >>>>> + if (max_dma_size < max_segment_size) >>>>> + max_segment_size = max_dma_size; >>>>> + } >>>>> >>>>> return max_segment_size; >>>>> } >>>>> diff --git a/include/linux/virtio.h b/include/linux/virtio.h >>>>> index b93238db94e3..1a605f408329 100644 >>>>> --- a/include/linux/virtio.h >>>>> +++ b/include/linux/virtio.h >>>>> @@ -147,7 +147,7 @@ int virtio_device_restore(struct virtio_device *dev); >>>>> #endif >>>>> void virtio_reset_device(struct virtio_device *dev); >>>>> >>>>> -size_t virtio_max_dma_size(const struct virtio_device *vdev); >>>>> +u32 virtio_max_dma_size(const struct virtio_device *vdev); >>>>> >>>>> #define virtio_device_for_each_vq(vdev, vq) \ >>>>> list_for_each_entry(vq, &vdev->vqs, list) >>>>> -- >>>>> 2.20.1 >>>>> >>> >
-- zhenwei pi
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