Re: [v6 1/5] vhost: skip crypto op fetch before vring init

[Maxime Coquelin <maxime.coquelin@redhat.com>]

Hi Gowri,

Thanks for the change, but I think there is an issue with the locking,
more below:

On 2/26/25 7:43 PM, Gowrishankar Muthukrishnan wrote:
> Until virtio avail ring is initialized (by VHOST_USER_SET_VRING_ADDR),
> worker thread should not try to fetch crypto op, which would lead to
> memory fault.
> 
> Fixes: 939066d96563 ("vhost/crypto: add public function implementation")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Gowrishankar Muthukrishnan <gmuthukrishn@marvell.com>
> Acked-by: Akhil Goyal <gakhil@marvell.com>
> ---
> v6:
>   - added lock checks.
> ---
>   lib/vhost/vhost_crypto.c | 20 ++++++++++++++++++++
>   1 file changed, 20 insertions(+)
> 
> diff --git a/lib/vhost/vhost_crypto.c b/lib/vhost/vhost_crypto.c
> index 3dc41a3bd5..d3d13eff07 100644
> --- a/lib/vhost/vhost_crypto.c
> +++ b/lib/vhost/vhost_crypto.c
> @@ -8,6 +8,7 @@
>   #include <rte_mbuf.h>
>   #include <rte_cryptodev.h>
>   
> +#include "iotlb.h"
>   #include "rte_vhost_crypto.h"
>   #include "vhost.h"
>   #include "vhost_user.h"
> @@ -1580,7 +1581,26 @@ rte_vhost_crypto_fetch_requests(int vid, uint32_t qid,
>   
>   	vq = dev->virtqueue[qid];
>   
> +	if (unlikely(vq == NULL)) {
> +		VC_LOG_ERR("Invalid virtqueue %u", qid);
> +		return 0;
> +	}
> +
> +	if (unlikely(rte_rwlock_read_trylock(&vq->access_lock) != 0))
> +		return 0;
> +
> +	vhost_user_iotlb_rd_lock(vq);
> +	if (unlikely(!vq->access_ok)) {
> +		VC_LOG_DBG("Virtqueue %u vrings not yet initialized", qid);
> +		vhost_user_iotlb_rd_unlock(vq);
> +		rte_rwlock_read_unlock(&vq->access_lock);
> +		return 0;
> +	}
> +
>   	avail_idx = *((volatile uint16_t *)&vq->avail->idx);
> +	vhost_user_iotlb_rd_unlock(vq);
> +	rte_rwlock_read_unlock(&vq->access_lock);
> +

You should only unlock at the end of the function, otherwise there is 
not much protection.

>   	start_idx = vq->last_used_idx;
>   	count = avail_idx - start_idx;
>   	count = RTE_MIN(count, VHOST_CRYPTO_MAX_BURST_SIZE);