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Date: Mon, 29 Apr 2024 03:02:13 -0400
From: "Michael S. Tsirkin" <mst@redhat.com>
To: Gavin Shan <gshan@redhat.com>
Cc: virtualization@lists.linux.dev, linux-kernel@vger.kernel.org,
	jasowang@redhat.com, shan.gavin@gmail.com
Subject: Re: [PATCH 0/4] vhost: Cleanup
Message-ID: <20240429025750-mutt-send-email-mst@kernel.org>
References: <20240423032407.262329-1-gshan@redhat.com>
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On Tue, Apr 23, 2024 at 01:24:03PM +1000, Gavin Shan wrote:
> This is suggested by Michael S. Tsirkin according to [1] and the goal
> is to apply smp_rmb() inside vhost_get_avail_idx() if needed. With it,
> the caller of the function needn't to worry about memory barriers. Since
> we're here, other cleanups are also applied.


Gavin I suggested another approach.
1. Start with the patch I sent (vhost: order avail ring reads after
   index updates) just do a diff against latest.
   simplify error handling a bit.
2. Do any other cleanups on top.

> [1] https://lore.kernel.org/virtualization/20240327075940-mutt-send-email-mst@kernel.org/
> 
> PATCH[1] drops the local variable @last_avail_idx since it's equivalent
>          to vq->last_avail_idx
> PATCH[2] improves vhost_get_avail_idx() so that smp_rmb() is applied if
>          needed. Besides, the sanity checks on the retrieved available
>          queue index are also squeezed to vhost_get_avail_idx()
> PATCH[3] improves vhost_get_avail_head(), similar to what we're doing
>          for vhost_get_avail_idx(), so that the relevant sanity checks
>          on the head are squeezed to vhost_get_avail_head()
> PATCH[4] Reformat vhost_{get, put}_user() by using tab instead of space
>          as the terminator for each line
> 
> Gavin Shan (4):
>   vhost: Drop variable last_avail_idx in vhost_get_vq_desc()
>   vhost: Improve vhost_get_avail_idx() with smp_rmb()
>   vhost: Improve vhost_get_avail_head()
>   vhost: Reformat vhost_{get, put}_user()
> 
>  drivers/vhost/vhost.c | 199 +++++++++++++++++++-----------------------
>  1 file changed, 88 insertions(+), 111 deletions(-)
> 
> -- 
> 2.44.0