From nobody Sun Feb 8 10:34:05 2026 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 C4F392E7BD9 for ; Mon, 20 Oct 2025 07:11:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760944279; cv=none; b=buIkeJzBzvuAK+EtzXEMskb8bDGyProghFvQFxXiC0PbvsoBX8PXavh9csuoR4qnt9aKQV6UypoZASGrb6f/Tg0y5Ibkt/nsfb56MvKSFNerxD+HLXR/qb+oniOb5Jk8Q8odwIzDRz0uxawsd0NbxhJCGDbyE0WeA5few6MHfUI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760944279; c=relaxed/simple; bh=zMSguGuKGxoHhvr1RW9fxPgjAuaWTQZtX5JJHzv8RbQ=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=mONpHrnghWPH6RAVbAk8d/gAg1FnBmaDan9VNONCGD+Lw1dOUFNHX/NCSltO54SVm+7H/8BbwOg6mPBiM4q7lshUqGGuzk/Llz4x+q/Bv8hErgeqPYjTLIsBc2QvQiYVUZY+mtY4bRhj/UXI0ZpzEZP2IoLjaC/VMnjqMYwolno= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=WNlipPfx; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="WNlipPfx" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1760944276; 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: in-reply-to:in-reply-to:references:references; bh=1fwTZo2nfDnQlgWZWhEhqf2fn4n6CrJWorLQA7f4krM=; b=WNlipPfx/QZH9MdfWZKMVA8NMrlFiDQvl9PthlFYjUqm90cZpFFhDYgprJRpmwgfmf7QOI c5LD406qjlJ42H0LalqckfMh301pf2L+qhkMNHtTQkrbvwjDiictoc1mfuKCtDxbvYXsG/ smkihzmnEC8i8ZWiQnQ3w4DRpQ28yg4= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-307-QpUd7TexPVebd4uq0DwCZA-1; Mon, 20 Oct 2025 03:11:13 -0400 X-MC-Unique: QpUd7TexPVebd4uq0DwCZA-1 X-Mimecast-MFC-AGG-ID: QpUd7TexPVebd4uq0DwCZA_1760944272 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D08D019560AF; Mon, 20 Oct 2025 07:11:12 +0000 (UTC) Received: from localhost.localdomain (unknown [10.72.113.29]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id D914A30001A2; Mon, 20 Oct 2025 07:11:09 +0000 (UTC) From: Jason Wang To: mst@redhat.com, jasowang@redhat.com, xuanzhuo@linux.alibaba.com, eperezma@redhat.com, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH V8 16/19] virtio_ring: factor out core logic for updating last_used_idx Date: Mon, 20 Oct 2025 15:10:00 +0800 Message-ID: <20251020071003.28834-17-jasowang@redhat.com> In-Reply-To: <20251020071003.28834-1-jasowang@redhat.com> References: <20251020071003.28834-1-jasowang@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Factor out the core logic for updating last_used_idx to be reused by the packed in order implementation. Acked-by: Eugenio P=C3=A9rez Reviewed-by: Xuan Zhuo Signed-off-by: Jason Wang --- drivers/virtio/virtio_ring.c | 43 +++++++++++++++++++++--------------- 1 file changed, 25 insertions(+), 18 deletions(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 16e432fda93d..c59e27e2ad68 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -1751,6 +1751,30 @@ static bool more_used_packed(const struct vring_virt= queue *vq) return virtqueue_poll_packed(vq, READ_ONCE(vq->last_used_idx)); } =20 +static void update_last_used_idx_packed(struct vring_virtqueue *vq, + u16 id, u16 last_used, + u16 used_wrap_counter) +{ + last_used +=3D vq->packed.desc_state[id].num; + if (unlikely(last_used >=3D vq->packed.vring.num)) { + last_used -=3D vq->packed.vring.num; + used_wrap_counter ^=3D 1; + } + + last_used =3D (last_used | (used_wrap_counter << VRING_PACKED_EVENT_F_WRA= P_CTR)); + WRITE_ONCE(vq->last_used_idx, last_used); + + /* + * If we expect an interrupt for the next entry, tell host + * by writing event index and flush out the write before + * the read in the next get_buf call. + */ + if (vq->packed.event_flags_shadow =3D=3D VRING_PACKED_EVENT_FLAG_DESC) + virtio_store_mb(vq->weak_barriers, + &vq->packed.vring.driver->off_wrap, + cpu_to_le16(vq->last_used_idx)); +} + static void *virtqueue_get_buf_ctx_packed(struct vring_virtqueue *vq, unsigned int *len, void **ctx) @@ -1794,24 +1818,7 @@ static void *virtqueue_get_buf_ctx_packed(struct vri= ng_virtqueue *vq, ret =3D vq->packed.desc_state[id].data; detach_buf_packed(vq, id, ctx); =20 - last_used +=3D vq->packed.desc_state[id].num; - if (unlikely(last_used >=3D vq->packed.vring.num)) { - last_used -=3D vq->packed.vring.num; - used_wrap_counter ^=3D 1; - } - - last_used =3D (last_used | (used_wrap_counter << VRING_PACKED_EVENT_F_WRA= P_CTR)); - WRITE_ONCE(vq->last_used_idx, last_used); - - /* - * If we expect an interrupt for the next entry, tell host - * by writing event index and flush out the write before - * the read in the next get_buf call. - */ - if (vq->packed.event_flags_shadow =3D=3D VRING_PACKED_EVENT_FLAG_DESC) - virtio_store_mb(vq->weak_barriers, - &vq->packed.vring.driver->off_wrap, - cpu_to_le16(vq->last_used_idx)); + update_last_used_idx_packed(vq, id, last_used, used_wrap_counter); =20 LAST_ADD_TIME_INVALID(vq); =20 --=20 2.31.1