From: Sergio Lopez <slp@redhat.com>
To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: "Kevin Wolf" <kwolf@redhat.com>, "Fam Zheng" <fam@euphon.net>,
qemu-block@nongnu.org, qemu-devel@nongnu.org,
"Max Reitz" <mreitz@redhat.com>,
"Philippe Mathieu-Daudé" <philmd@redhat.com>
Subject: Re: [PATCH 3/7] block/nvme: don't access CQE after moving cq.head
Date: Mon, 25 May 2020 10:12:41 +0200 [thread overview]
Message-ID: <20200525081241.cbsgtyi6pf7dkyyf@dritchie> (raw)
In-Reply-To: <20200519171138.201667-4-stefanha@redhat.com>
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On Tue, May 19, 2020 at 06:11:34PM +0100, Stefan Hajnoczi wrote:
> Do not access a CQE after incrementing q->cq.head and releasing q->lock.
> It is unlikely that this causes problems in practice but it's a latent
> bug.
>
> The reason why it should be safe at the moment is that completion
> processing is not re-entrant and the CQ doorbell isn't written until the
> end of nvme_process_completion().
>
> Make this change now because QEMU expects completion processing to be
> re-entrant and later patches will do that.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
> block/nvme.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
Reviewed-by: Sergio Lopez <slp@redhat.com>
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next prev parent reply other threads:[~2020-05-25 8:13 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-19 17:11 [PATCH 0/7] block/nvme: support nested aio_poll() Stefan Hajnoczi
2020-05-19 17:11 ` [PATCH 1/7] block/nvme: poll queues without q->lock Stefan Hajnoczi
2020-05-25 8:07 ` Sergio Lopez
2020-05-28 15:23 ` Stefan Hajnoczi
2020-05-29 7:49 ` Sergio Lopez
2020-06-17 12:52 ` Stefan Hajnoczi
2020-05-19 17:11 ` [PATCH 2/7] block/nvme: drop tautologous assertion Stefan Hajnoczi
2020-05-25 8:08 ` Sergio Lopez
2020-05-26 12:00 ` Philippe Mathieu-Daudé
2020-05-19 17:11 ` [PATCH 3/7] block/nvme: don't access CQE after moving cq.head Stefan Hajnoczi
2020-05-25 8:12 ` Sergio Lopez [this message]
2020-05-26 12:03 ` Philippe Mathieu-Daudé
2020-05-19 17:11 ` [PATCH 4/7] block/nvme: switch to a NVMeRequest freelist Stefan Hajnoczi
2020-05-25 8:10 ` Sergio Lopez
2020-05-19 17:11 ` [PATCH 5/7] block/nvme: clarify that free_req_queue is protected by q->lock Stefan Hajnoczi
2020-05-25 8:13 ` Sergio Lopez
2020-05-26 12:04 ` Philippe Mathieu-Daudé
2020-05-19 17:11 ` [PATCH 6/7] block/nvme: keep BDRVNVMeState pointer in NVMeQueuePair Stefan Hajnoczi
2020-05-25 8:22 ` Sergio Lopez
2020-05-26 14:55 ` Philippe Mathieu-Daudé
2020-05-26 15:20 ` Philippe Mathieu-Daudé
2020-05-28 15:25 ` Stefan Hajnoczi
2020-05-19 17:11 ` [PATCH 7/7] block/nvme: support nested aio_poll() Stefan Hajnoczi
2020-05-25 8:26 ` Sergio Lopez
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