From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E5E061C03 for ; Mon, 20 Mar 2023 15:04:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 663AEC433EF; Mon, 20 Mar 2023 15:04:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1679324697; bh=FMbUqgL0lq5swos4No6ff30OTTxdiyKWbGJBYOaTgj0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=H8gKb0xkspu7PVJHGgsQZOV6m6Emk3ynfzR3Q2wroNjFS0wAEg2H2+KGUaoZqibtM eLJFyQGXbxpbVoLcBf5IZVEze+2mawm/z54PyiMRuxkedVya9RglFuey9CMMWCxyt9 hdtUKz0FzOtZW6JmqgaWIRRQm9OqDsvTF0A0OJ90= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Stefano Garzarella , =?UTF-8?q?Eugenio=20P=C3=A9rez?= , "Michael S. Tsirkin" , Sasha Levin Subject: [PATCH 5.15 019/115] vdpa_sim: set last_used_idx as last_avail_idx in vdpasim_queue_ready Date: Mon, 20 Mar 2023 15:53:51 +0100 Message-Id: <20230320145450.214072736@linuxfoundation.org> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230320145449.336983711@linuxfoundation.org> References: <20230320145449.336983711@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Eugenio Pérez [ Upstream commit b4cca6d48eb3fa6f0d9caba4329b1a2b0ff67a77 ] Starting from an used_idx different than 0 is needed in use cases like virtual machine migration. Not doing so and letting the caller set an avail idx different than 0 causes destination device to try to use old buffers that source driver already recover and are not available anymore. Since vdpa_sim does not support receive inflight descriptors as a destination of a migration, let's set both avail_idx and used_idx the same at vq start. This is how vhost-user works in a VHOST_SET_VRING_BASE call. Although the simple fix is to set last_used_idx at vdpasim_set_vq_state, it would be reset at vdpasim_queue_ready. The last_avail_idx case is fixed with commit 0e84f918fac8 ("vdpa_sim: not reset state in vdpasim_queue_ready"). Since the only option is to make it equal to last_avail_idx, adding the only change needed here. This was discovered and tested live migrating the vdpa_sim_net device. Fixes: 2c53d0f64c06 ("vdpasim: vDPA device simulator") Reviewed-by: Stefano Garzarella Signed-off-by: Eugenio Pérez Message-Id: <20230302181857.925374-1-eperezma@redhat.com> Signed-off-by: Michael S. Tsirkin Signed-off-by: Sasha Levin --- drivers/vdpa/vdpa_sim/vdpa_sim.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c index eeda45fbba258..3ccefa58e405c 100644 --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c @@ -75,6 +75,17 @@ static void vdpasim_queue_ready(struct vdpasim *vdpasim, unsigned int idx) (uintptr_t)vq->device_addr); vq->vring.last_avail_idx = last_avail_idx; + + /* + * Since vdpa_sim does not support receive inflight descriptors as a + * destination of a migration, let's set both avail_idx and used_idx + * the same at vq start. This is how vhost-user works in a + * VHOST_SET_VRING_BASE call. + * + * Although the simple fix is to set last_used_idx at + * vdpasim_set_vq_state, it would be reset at vdpasim_queue_ready. + */ + vq->vring.last_used_idx = last_avail_idx; vq->vring.notify = vdpasim_vq_notify; } -- 2.39.2