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bh=sp0y+Zg3ajzpKsP0+NwKrmoN1WDadhwx00K7pgQg8F8=; b=M0wx699MizNFBq1HYFNdWxBNgv7Et0AgRhbCXFtbP9qqFcZ8K73Ml6hUem+kpYaEx14Vct dOs0sIIFjgEQUoKl16ON4tLqVZKibedaAZaBUAwhp5tiPtVO9pnjVtZSpqaCFHsUO7U/Np QPwWzqjyAxf0JiGMVrDIkqX05plmyZU= X-MC-Unique: qvQAiZXwNVOduU4I477xxA-1 From: Stefan Hajnoczi To: qemu-devel@nongnu.org Subject: [PATCH 3/7] block/nvme: don't access CQE after moving cq.head Date: Tue, 19 May 2020 18:11:34 +0100 Message-Id: <20200519171138.201667-4-stefanha@redhat.com> In-Reply-To: <20200519171138.201667-1-stefanha@redhat.com> References: <20200519171138.201667-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=207.211.31.120; 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charset="utf-8" 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 Reviewed-by: Philippe Mathieu-Daud=C3=A9 Reviewed-by: Sergio Lopez --- block/nvme.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/block/nvme.c b/block/nvme.c index 5286227074..6bf58bc6aa 100644 --- a/block/nvme.c +++ b/block/nvme.c @@ -321,11 +321,14 @@ static bool nvme_process_completion(BDRVNVMeState *s,= NVMeQueuePair *q) q->busy =3D true; assert(q->inflight >=3D 0); while (q->inflight) { + int ret; int16_t cid; + c =3D (NvmeCqe *)&q->cq.queue[q->cq.head * NVME_CQ_ENTRY_BYTES]; if ((le16_to_cpu(c->status) & 0x1) =3D=3D q->cq_phase) { break; } + ret =3D nvme_translate_error(c); q->cq.head =3D (q->cq.head + 1) % NVME_QUEUE_SIZE; if (!q->cq.head) { q->cq_phase =3D !q->cq_phase; @@ -344,7 +347,7 @@ static bool nvme_process_completion(BDRVNVMeState *s, N= VMeQueuePair *q) preq->busy =3D false; preq->cb =3D preq->opaque =3D NULL; qemu_mutex_unlock(&q->lock); - req.cb(req.opaque, nvme_translate_error(c)); + req.cb(req.opaque, ret); qemu_mutex_lock(&q->lock); q->inflight--; progress =3D true; --=20 2.25.3