From nobody Tue Nov 04 14:36:09 2025 X-Original-To: dev-commits-src-all@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4d19xQ1PPxz6G9fT; Tue, 04 Nov 2025 14:36:10 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "R12" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4d19xP5xdCz3CRF; Tue, 04 Nov 2025 14:36:09 +0000 (UTC) (envelope-from git@FreeBSD.org) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1762266969; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=qrZsklW3/OABHytn+8ta20rb/LLFP2SarFlmkwzzXzw=; b=FLT3mZexMieumL8/p1UfurTX6/jqD6dpGN4d4z3Mm7RFeZLr1HU3FxzEqRserPyX+yvxo1 3fNH96kyHAkdsy5BVo4K4jO3ro71Twv0+Rli29h68jGp5Vdw8JdcAFtmBBeq8uNJ37rSfC Ar6AN0Y0F2T0yBRbnqx12yWIo/4mm7j14WaKqDRPPcSymSd/TwXwephJr53nXMKqoeVGGB pQtrzlLA1rbMZMGCnwnZ1XGUj+iYZWHCuCVQ8cZ92UP3Mp1k0rfEIfaugv6GPohbNuA6Ja U25ojYhejwmtZVWUOG2FeJKRX743sx7m2L1Qxrp6EHk5Dy5wEVgJAFSp7jfqfg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1762266969; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=qrZsklW3/OABHytn+8ta20rb/LLFP2SarFlmkwzzXzw=; b=xzZCu+4+RIkeOpCzO9EZJ7poDpNB8DvcOI7qeSW6f2T46Gw7HDh+tfUeInZksSojEWojHy DvrXywBZXNDFFnllC2cAqnTf1E5JBWrqnMAKZ/d1TnlGWxjgbR4CzaEiDPZ6NUFUWA042a nOlq4PPq/578q8CFpkscFkCpYyIyorGJrPFdQy/dXr6VAlEAZvyv3h59X4IEnMYCb/Kg8B a6VWLSf2us36oKk+jv14MqcLnj83BcvAhwv0y+c8yaDtiGea/4mBdMj/EBYpETJt3WUKg4 wDofgJa20lGcfhiQ13RDfEoVNX3Eshzoct7WQbe3806yTUJP3jg8CSE9g7iYug== ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1762266969; a=rsa-sha256; cv=none; b=VaqcZcFM/cWM/vuTk8+LRiani+i2SysAPxkpV0/liXw51XX7aJw+EX+64v9LxA0E/GcfHw GBKFcWq87gnfQ2zLX/t5OXTTsWKb9Ga8zQExlZZ78TELguqaVZf0X3WQ704qCnv6aORGm6 POLMcz8hchdnlosttVaUjkuDBLBa33tP7WDsCsbjf4/xqAuHFHoOcsjN4sQ+34YMjO76iK T7YQNjuBio+a3MAGPkWXZWLcoZyhcHgAIdkhUZb58UVHWt8is978thJqYgm80xEoamhGcS jfPLAO46gpqzEUl0C9j7qZb9cxeWP0NpoCMaZ8xCGSk9cWAbk70z6A9/x1L5Vw== ARC-Authentication-Results: i=1; mx1.freebsd.org; none Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 4d19xP5WYrz11LN; Tue, 04 Nov 2025 14:36:09 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org ([127.0.1.44]) by gitrepo.freebsd.org (8.18.1/8.18.1) with ESMTP id 5A4Ea978004929; Tue, 4 Nov 2025 14:36:09 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.18.1/8.18.1/Submit) id 5A4Ea9x8004926; Tue, 4 Nov 2025 14:36:09 GMT (envelope-from git) Date: Tue, 4 Nov 2025 14:36:09 GMT Message-Id: <202511041436.5A4Ea9x8004926@gitrepo.freebsd.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org From: Mark Johnston Subject: git: f999ffdce381 - main - virtio: Fix polling in virtqueue_dequeue() List-Id: Commit messages for all branches of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-all List-Help: List-Post: List-Subscribe: List-Unsubscribe: X-BeenThere: dev-commits-src-all@freebsd.org Sender: owner-dev-commits-src-all@FreeBSD.org MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: markj X-Git-Repository: src X-Git-Refname: refs/heads/main X-Git-Reftype: branch X-Git-Commit: f999ffdce3813eb946f10999ccffb8275c324469 Auto-Submitted: auto-generated The branch main has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=f999ffdce3813eb946f10999ccffb8275c324469 commit f999ffdce3813eb946f10999ccffb8275c324469 Author: Mark Johnston AuthorDate: 2025-11-04 14:27:33 +0000 Commit: Mark Johnston CommitDate: 2025-11-04 14:35:31 +0000 virtio: Fix polling in virtqueue_dequeue() The access of vq->vq_ring.used->idx needs to be volatile-qualified, otherwise the compiler may optimize virtqueue_poll() into an infinite loop if there is no data available upon the first poll. Prior to commit ad17789a8569 this wasn't a problem since an external function call after each poll inhibited the optimization. PR: 289930 MFC after: 3 days Sponsored by: Klara, Inc. Fixes: ad17789a8569 ("virtio: Remove the unused poll method") --- sys/dev/virtio/virtqueue.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/sys/dev/virtio/virtqueue.c b/sys/dev/virtio/virtqueue.c index cc7a233d60ee..41e01549c8b2 100644 --- a/sys/dev/virtio/virtqueue.c +++ b/sys/dev/virtio/virtqueue.c @@ -580,7 +580,8 @@ virtqueue_dequeue(struct virtqueue *vq, uint32_t *len) void *cookie; uint16_t used_idx, desc_idx; - if (vq->vq_used_cons_idx == vq_htog16(vq, vq->vq_ring.used->idx)) + if (vq->vq_used_cons_idx == + vq_htog16(vq, atomic_load_16(&vq->vq_ring.used->idx))) return (NULL); used_idx = vq->vq_used_cons_idx++ & (vq->vq_nentries - 1);