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vhost: fix double read of descriptor flags

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Flags could be updated in a separate process leading to the
inconsistent check.

Additionally, read marked as 'volatile' to highlight the shared
nature of the variable and avoid such issues in the future.

Fixes: d3211c98c4 ("vhost: add helpers for packed virtqueues")
Cc: stable@dpdk.org

Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
This commit is contained in:
Ilya Maximets 2018-12-05 18:09:26 +03:00 committed by Ferruh Yigit
parent 81e5cdf19e
commit 48cae0bfa6
1 changed files with 4 additions and 2 deletions
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6
lib/librte_vhost/vhost.h
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@ -393,8 +393,10 @@ vq_is_packed(struct virtio_net *dev)
static inline bool
desc_is_avail(struct vring_packed_desc *desc, bool wrap_counter)
{
return wrap_counter == !!(desc->flags & VRING_DESC_F_AVAIL) &&
wrap_counter != !!(desc->flags & VRING_DESC_F_USED);
uint16_t flags = *((volatile uint16_t *) &desc->flags);
return wrap_counter == !!(flags & VRING_DESC_F_AVAIL) &&
wrap_counter != !!(flags & VRING_DESC_F_USED);
}
#define VHOST_LOG_PAGE 4096