From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C92EFC11F76 for ; Sat, 10 Jul 2021 23:50:19 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 85AF5613F9 for ; Sat, 10 Jul 2021 23:50:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 85AF5613F9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=virtualization-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id 5E6FB404E5; Sat, 10 Jul 2021 23:50:19 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id a_79pfD5P4HI; Sat, 10 Jul 2021 23:50:17 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp4.osuosl.org (Postfix) with ESMTPS id 6D6A8404E3; Sat, 10 Jul 2021 23:50:16 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id E9823C0023; Sat, 10 Jul 2021 23:50:15 +0000 (UTC) Received: from smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by lists.linuxfoundation.org (Postfix) with ESMTP id 99156C000E for ; Sat, 10 Jul 2021 23:50:14 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id 7B48A400F5 for ; Sat, 10 Jul 2021 23:50:14 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Authentication-Results: smtp2.osuosl.org (amavisd-new); dkim=pass (2048-bit key) header.d=kernel.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ULgg3CGrjFPi for ; Sat, 10 Jul 2021 23:50:13 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp2.osuosl.org (Postfix) with ESMTPS id E01BC400AB for ; Sat, 10 Jul 2021 23:50:13 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 05D89613C2; Sat, 10 Jul 2021 23:50:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1625961013; bh=EqY3s3uZCH/3kT+7Qix6kDh4PwexwXrGB3dJQFtlQJc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TIzjdW0q7LUQFDupWP3p4HSFXsiFkvsoC9jO30O74WMsW6xSTye6KwzIJRwMZIjmb M537B1stjnovX+TUFx/A3QyGavwXv9RcX/k7w069RFgUN70cm5gqSHnNNJl9es+wfS /mAQG1BCd2SdCTdXF3Tk9Ax1QNarDOvhAYymiqiaL1P2nFyLB7QKq9X0AJskZPHIHz x9mhi61DoWqv4YQ0UD7ysdIAwRl3xxSagnQRiyeG1YGzqK7HcYleeE7ONfDMGbZonR CmgnLgwJpRypWmAaZ0iQVF5w2ZUD2bKp8KtNjASyOcPvXqQQ0KjPBq3IGSs5B4wl/m o6Bu9UGjThgjg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH AUTOSEL 5.12 42/43] virtio: fix up virtio_disable_cb Date: Sat, 10 Jul 2021 19:49:14 -0400 Message-Id: <20210710234915.3220342-42-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210710234915.3220342-1-sashal@kernel.org> References: <20210710234915.3220342-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Cc: Sasha Levin , virtualization@lists.linux-foundation.org, "Michael S. Tsirkin" X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" From: "Michael S. Tsirkin" [ Upstream commit 8d622d21d24803408b256d96463eac4574dcf067 ] virtio_disable_cb is currently a nop for split ring with event index. This is because it used to be always called from a callback when we know device won't trigger more events until we update the index. However, now that we run with interrupts enabled a lot we also poll without a callback so that is different: disabling callbacks will help reduce the number of spurious interrupts. Further, if using event index with a packed ring, and if being called from a callback, we actually do disable interrupts which is unnecessary. Fix both issues by tracking whenever we get a callback. If that is the case disabling interrupts with event index can be a nop. If not the case disable interrupts. Note: with a split ring there's no explicit "no interrupts" value. For now we write a fixed value so our chance of triggering an interupt is 1/ring size. It's probably better to write something related to the last used index there to reduce the chance even further. For now I'm keeping it simple. Signed-off-by: Michael S. Tsirkin Signed-off-by: Sasha Levin --- drivers/virtio/virtio_ring.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 71e16b53e9c1..88f0b16b11b8 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -113,6 +113,9 @@ struct vring_virtqueue { /* Last used index we've seen. */ u16 last_used_idx; + /* Hint for event idx: already triggered no need to disable. */ + bool event_triggered; + union { /* Available for split ring */ struct { @@ -739,7 +742,10 @@ static void virtqueue_disable_cb_split(struct virtqueue *_vq) if (!(vq->split.avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) { vq->split.avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT; - if (!vq->event) + if (vq->event) + /* TODO: this is a hack. Figure out a cleaner value to write. */ + vring_used_event(&vq->split.vring) = 0x0; + else vq->split.vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->split.avail_flags_shadow); @@ -1605,6 +1611,7 @@ static struct virtqueue *vring_create_virtqueue_packed( vq->weak_barriers = weak_barriers; vq->broken = false; vq->last_used_idx = 0; + vq->event_triggered = false; vq->num_added = 0; vq->packed_ring = true; vq->use_dma_api = vring_use_dma_api(vdev); @@ -1919,6 +1926,12 @@ void virtqueue_disable_cb(struct virtqueue *_vq) { struct vring_virtqueue *vq = to_vvq(_vq); + /* If device triggered an event already it won't trigger one again: + * no need to disable. + */ + if (vq->event_triggered) + return; + if (vq->packed_ring) virtqueue_disable_cb_packed(_vq); else @@ -1942,6 +1955,9 @@ unsigned virtqueue_enable_cb_prepare(struct virtqueue *_vq) { struct vring_virtqueue *vq = to_vvq(_vq); + if (vq->event_triggered) + vq->event_triggered = false; + return vq->packed_ring ? virtqueue_enable_cb_prepare_packed(_vq) : virtqueue_enable_cb_prepare_split(_vq); } @@ -2005,6 +2021,9 @@ bool virtqueue_enable_cb_delayed(struct virtqueue *_vq) { struct vring_virtqueue *vq = to_vvq(_vq); + if (vq->event_triggered) + vq->event_triggered = false; + return vq->packed_ring ? virtqueue_enable_cb_delayed_packed(_vq) : virtqueue_enable_cb_delayed_split(_vq); } @@ -2044,6 +2063,10 @@ irqreturn_t vring_interrupt(int irq, void *_vq) if (unlikely(vq->broken)) return IRQ_HANDLED; + /* Just a hint for performance: so it's ok that this can be racy! */ + if (vq->event) + vq->event_triggered = true; + pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback); if (vq->vq.callback) vq->vq.callback(&vq->vq); @@ -2083,6 +2106,7 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index, vq->weak_barriers = weak_barriers; vq->broken = false; vq->last_used_idx = 0; + vq->event_triggered = false; vq->num_added = 0; vq->use_dma_api = vring_use_dma_api(vdev); #ifdef DEBUG -- 2.30.2 _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization