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SubjectRe: [PATCH] vhost: Fix compile time error
On Sat, Sep 14, 2019 at 01:44:57AM -0700, Guenter Roeck wrote:
> Building vhost on 32-bit targets results in the following error.
>
> drivers/vhost/vhost.c: In function 'translate_desc':
> include/linux/compiler.h:549:38: error:
> call to '__compiletime_assert_1879' declared with attribute error:
> BUILD_BUG_ON failed: sizeof(_s) > sizeof(long)
>
> Fixes: a89db445fbd7 ("vhost: block speculation of translated descriptors")
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Jason Wang <jasowang@redhat.com>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>



> ---
> drivers/vhost/vhost.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index acabf20b069e..102a0c877007 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -2074,7 +2074,7 @@ static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len,
> _iov->iov_base = (void __user *)
> ((unsigned long)node->userspace_addr +
> array_index_nospec((unsigned long)(addr - node->start),
> - node->size));
> + (unsigned long)node->size));

Unfortunately this does not fix the case where size is actually 64 bit,
e.g. a single node with VA 0, size 2^32 is how
you cover the whole virtual address space.

this is not how qemu uses it, but it's valid.

I think it's best to just revert the patch for now.

> s += size;
> addr += size;
> ++ret;
> --
> 2.7.4

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