From nobody Mon Feb 9 05:59:13 2026 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 A53AB32ABFA for ; Wed, 24 Dec 2025 00:34:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766536466; cv=none; b=SclT2WP/69P6tc5PKOnmOvCKgqUINw+pV2M1PQa2OkLzNbv3j7XFiDPZdbd0uPIdGmOIzRomc078XPFLa3hbdwTCWxdUHVD8pgXuZfnrj4OdRVK2BwxLolg1ZL3ar66B6Og8pX6k3ylAZ8GIG0M8cclrf2aZW2h1D79dJVfmW2o= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766536466; c=relaxed/simple; bh=Pa2ZCzCN7t9uJB+Pc5UCPIuumMntNFVq4uNGsRTwL4w=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=Oa6Vl85MM0LPAuVcCuU8ERySW/cBErG94Xy1giYXJsrZFGXsUqlYFEz/IMTNb+nSsONpAIMsXjm4rfP672bA9KuOP0S8A//ibcj7OJVWnxoiS2QHiydDkgkqWWTiwRErOYFYMgM5s3j6LQqqVKgUuZaMYCNwyORGAMLDy+wcbWc= 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=dL9BmVTQ; arc=none smtp.client-ip=170.10.133.124 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="dL9BmVTQ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1766536463; 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=tEtpQLaljBtSXDOnL/9S1Y9vQ4v4DQESj/yD1ikXbLg=; b=dL9BmVTQYj/e9uDXDjIDzO4anlvgDZmd3j470RuglovKOEMSRb35kVoEfisq2yyBaKmjpe rNhmJktUlkrnLDV/6pdye8FzZ91Twdo7IwKVy0fIxy5RcPfSrJCxCpCY4SUgpZMxk2E3Ih QGFkRSpaiMgTTDcG0R73/dcr32h4luM= Received: from mx-prod-mc-03.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-350-JuzFvjv3PdGXq7bqphB0Jw-1; Tue, 23 Dec 2025 19:34:20 -0500 X-MC-Unique: JuzFvjv3PdGXq7bqphB0Jw-1 X-Mimecast-MFC-AGG-ID: JuzFvjv3PdGXq7bqphB0Jw_1766536459 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 2C91719560B2; Wed, 24 Dec 2025 00:34:19 +0000 (UTC) Received: from localhost.localdomain (unknown [10.72.112.39]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 27C9919560AB; Wed, 24 Dec 2025 00:34:15 +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 V10 16/19] virtio_ring: factor out core logic for updating last_used_idx Date: Wed, 24 Dec 2025 08:33:06 +0800 Message-ID: <20251224003309.23432-17-jasowang@redhat.com> In-Reply-To: <20251224003309.23432-1-jasowang@redhat.com> References: <20251224003309.23432-1-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 3.0 on 10.30.177.17 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 ca33af830f65..9e3213f6083d 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -1756,6 +1756,30 @@ 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) @@ -1799,24 +1823,7 @@ 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