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Re: [Qemu-devel] [PATCH 09/10] virtio: read avail_idx from VQ only when

From: Cornelia Huck
Subject: Re: [Qemu-devel] [PATCH 09/10] virtio: read avail_idx from VQ only when necessary
Date: Tue, 19 Jan 2016 17:20:34 +0100

On Fri, 15 Jan 2016 13:41:57 +0100
Paolo Bonzini <address@hidden> wrote:

> From: Vincenzo Maffione <address@hidden>
> The virtqueue_pop() implementation needs to check if the avail ring
> contains some pending buffers. To perform this check, it is not
> always necessary to fetch the avail_idx in the VQ memory, which is
> expensive. This patch introduces a shadow variable tracking avail_idx
> and modifies virtio_queue_empty() to access avail_idx in physical
> memory only when necessary.
> Signed-off-by: Vincenzo Maffione <address@hidden>
> Message-Id: <address@hidden>
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
>  hw/virtio/virtio.c | 25 +++++++++++++++++++++----
>  1 file changed, 21 insertions(+), 4 deletions(-)

Reviewed-by: Cornelia Huck <address@hidden>

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