Re: [PATCH] kvm tools: Support virtio indirect buffers

[Cyrill Gorcunov <gorcunov@gmail.com>]

On Mon, Nov 28, 2011 at 07:54:27PM +0200, Sasha Levin wrote:
>  
> +/*
> + * Each buffer in the virtqueues is actually a chain of descriptors.  This
> + * function returns the next descriptor in the chain, or vq->vring.num if we're
> + * at the end.
> + */
> +static unsigned next_desc(struct vring_desc *desc,
> +			  unsigned int i, unsigned int max)
> +{
> +	unsigned int next;
> +
> +	/* If this descriptor says it doesn't chain, we're done. */
> +	if (!(desc[i].flags & VRING_DESC_F_NEXT))
> +		return max;
> +
> +	/* Check they're not leading us off end of descriptors. */
> +	next = desc[i].next;
> +	/* Make sure compiler knows to grab that: we don't want it changing! */
> +	wmb();
> +
> +	return next;
> +}
> +

Hi Sasha, where the rmb() then? Or maybe you wanted plain barrier() here?