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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4ABBDC433EF for ; Thu, 9 Dec 2021 06:55:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233358AbhLIG7b (ORCPT ); Thu, 9 Dec 2021 01:59:31 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:57533 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231517AbhLIG7a (ORCPT ); Thu, 9 Dec 2021 01:59:30 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1639032957; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=/fb62qxVVfvgceW+7mro5MbYtbA/njW6uOUzofuzKQ0=; b=UxFqxRvhXqyOcAKDfeSZkzHInE3CqoJixcBoQvKLX0BH9MzwYwSJ/DQkxvEoEK/OWH0qGn KAWfxAiwCCg5BKxZLZ1WZwEBrSTKY8aMHXmYUyA5yWrbuPO959l2XmDG0WX4tiVp5nb0ej SHCh01oe2Z/86Y/9ydX6V2v9wIVQX1o= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-604-z_kG2imVMRqXFyhJqggduA-1; Thu, 09 Dec 2021 01:55:55 -0500 X-MC-Unique: z_kG2imVMRqXFyhJqggduA-1 Received: by mail-wm1-f72.google.com with SMTP id k25-20020a05600c1c9900b00332f798ba1dso4378106wms.4 for ; Wed, 08 Dec 2021 22:55:55 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=/fb62qxVVfvgceW+7mro5MbYtbA/njW6uOUzofuzKQ0=; b=R0tYgkhjRk6iRMH+8B6P6CeS4Zu7anWp/lC4RoFrryJBPdOQqLIE6iJsqJACJX9ngO Vn0ymReqekXiXiB3Y58CqQQCnLglxfjbL1GyTGQqFbKgmf7/6e18Fh1eFLfvdnQtdbII uPYtgaCV08mw6yDDHyig73t7t4H3tLsYW5xCEbSsQJScxTPmnDQkOuAy1mw9nTNKWECG eKtt1P2iCq6pBPXvlDQS8iQNAvWSq/aEiLTWV6c7rt+ocqT/wg43Q7WuufRMkhPkBVBj 9Ncz3jYO4HDUHsz24FhOK4u0t6IWp4qDgb3huXRwxB2DsTKjMZ3gQgLS2qQtoyTE18rG OC4g== X-Gm-Message-State: AOAM533kMhnEwN72Pv5MCijAkt+h5XFvxp2t4IaK1weA4OpDDHqPcint HBSTMiKGifwbpwlVELwxY461iPu4FaR/BUyB0MO563KXCQ12b7sdY/qE1pziv+TTcBFkHQCQvfX WaX0vX/PtYVDyRHHk76TzdCAX X-Received: by 2002:a7b:c1cb:: with SMTP id a11mr4835612wmj.30.1639032954444; Wed, 08 Dec 2021 22:55:54 -0800 (PST) X-Google-Smtp-Source: ABdhPJxFjgkHORRhDzdGFhtR2vh0mcJ117Rtzn0FOi+3LPmzp4mLAvIEY2WhtWYopTY+U6sr6lywbQ== X-Received: by 2002:a7b:c1cb:: with SMTP id a11mr4835591wmj.30.1639032954203; Wed, 08 Dec 2021 22:55:54 -0800 (PST) Received: from redhat.com ([2.55.18.120]) by smtp.gmail.com with ESMTPSA id l26sm4927855wms.15.2021.12.08.22.55.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Dec 2021 22:55:53 -0800 (PST) Date: Thu, 9 Dec 2021 01:55:50 -0500 From: "Michael S. Tsirkin" To: Jason Wang Cc: virtualization , linux-kernel Subject: Re: [PATCH V2] virtio-mmio: harden interrupt Message-ID: <20211209015205-mutt-send-email-mst@kernel.org> References: <20211126044102.18374-1-jasowang@redhat.com> <20211208151801-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 09, 2021 at 10:06:34AM +0800, Jason Wang wrote: > On Thu, Dec 9, 2021 at 4:27 AM Michael S. Tsirkin wrote: > > > > On Fri, Nov 26, 2021 at 12:41:02PM +0800, Jason Wang wrote: > > > This patch tries to make sure the virtio interrupt handler for MMIO > > > won't be called after a reset and before virtio_device_ready(). We > > > can't use IRQF_NO_AUTOEN since we're using shared interrupt > > > (IRQF_SHARED). So this patch tracks the interrupt enabling status in a > > > new intr_soft_enabled variable and toggle it during in > > > vm_disable/enable_interrupts(). The MMIO interrupt handler will check > > > intr_soft_enabled before processing the actual interrupt. > > > > > > Signed-off-by: Jason Wang > > > --- > > > Changes since V1: > > > - Silent compling warnings > > > drivers/virtio/virtio_mmio.c | 37 ++++++++++++++++++++++++++++++++++++ > > > 1 file changed, 37 insertions(+) > > > > > > diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c > > > index 56128b9c46eb..c517afdd2cc5 100644 > > > --- a/drivers/virtio/virtio_mmio.c > > > +++ b/drivers/virtio/virtio_mmio.c > > > @@ -90,6 +90,7 @@ struct virtio_mmio_device { > > > /* a list of queues so we can dispatch IRQs */ > > > spinlock_t lock; > > > struct list_head virtqueues; > > > + bool intr_soft_enabled; > > > }; > > > > > > struct virtio_mmio_vq_info { > > > @@ -100,7 +101,37 @@ struct virtio_mmio_vq_info { > > > struct list_head node; > > > }; > > > > > > +/* disable irq handlers */ > > > +static void vm_disable_cbs(struct virtio_device *vdev) > > > +{ > > > + struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev); > > > + int irq = platform_get_irq(vm_dev->pdev, 0); > > > > > > + /* > > > + * The below synchronize() guarantees that any > > > + * interrupt for this line arriving after > > > + * synchronize_irq() has completed is guaranteed to see > > > + * intx_soft_enabled == false. > > > + */ > > > + WRITE_ONCE(vm_dev->intr_soft_enabled, false); > > > + synchronize_irq(irq); > > > +} > > > + > > > +/* enable irq handlers */ > > > +static void vm_enable_cbs(struct virtio_device *vdev) > > > +{ > > > + struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev); > > > + int irq = platform_get_irq(vm_dev->pdev, 0); > > > + > > > + disable_irq(irq); > > > + /* > > > + * The above disable_irq() provides TSO ordering and > > > + * as such promotes the below store to store-release. > > > + */ > > > + WRITE_ONCE(vm_dev->intr_soft_enabled, true); > > > + enable_irq(irq); > > > + return; > > > +} > > > > > > /* Configuration interface */ > > > > > > @@ -262,6 +293,8 @@ static void vm_reset(struct virtio_device *vdev) > > > > > > /* 0 status means a reset. */ > > > writel(0, vm_dev->base + VIRTIO_MMIO_STATUS); > > > > There was a discussion about reading status to make sure it is clear. > > The spec says we should, this can't hurt as a further hardening measure. > > In fact, let's do it in the core maybe? Spec says it applies to all > > devices ... > > We can do that, but I'm not sure if we break some existing device. Hmm. Have anything specific in mind? > > > > > + /* Disable VQ/configuration callbacks. */ > > > + vm_disable_cbs(vdev); > > > } > > > > > > > > > @@ -288,6 +321,9 @@ static irqreturn_t vm_interrupt(int irq, void *opaque) > > > unsigned long flags; > > > irqreturn_t ret = IRQ_NONE; > > > > > > + if (!READ_ONCE(vm_dev->intr_soft_enabled)) > > > + return IRQ_NONE; > > > + > > > > So if the write is seen before reset happened (should not happen, but we > > are talking a buggy device) then it won't be acknowledged and device > > will keep pulling the interrupt. I think as long as we are hardening > > this, let's go the full mile and try to avoid DoS if we can, do the > > check before invoking the callback, but do not skip the read. > > Whether to still return IRQ_NONE is a good question. > > Did you mean something like this: > > /* Read and acknowledge interrupts */ > status = readl(vm_dev->base + VIRTIO_MMIO_INTERRUPT_STATUS); > writel(status, vm_dev->base + VIRTIO_MMIO_INTERRUPT_ACK); > > if (status) > ret = IRQ_HANDLED; > > if (!READ_ONCE(vm_dev->intr_soft_enabled)) > return ret; > > Thanks Maybe. Or is if (!READ_ONCE(vm_dev->intr_soft_enabled)) return IRQ_NONE; better here? > > > > > > > > > > > /* Read and acknowledge interrupts */ > > > status = readl(vm_dev->base + VIRTIO_MMIO_INTERRUPT_STATUS); > > > writel(status, vm_dev->base + VIRTIO_MMIO_INTERRUPT_ACK); > > > @@ -529,6 +565,7 @@ static bool vm_get_shm_region(struct virtio_device *vdev, > > > } > > > > > > static const struct virtio_config_ops virtio_mmio_config_ops = { > > > + .enable_cbs = vm_enable_cbs, > > > .get = vm_get, > > > .set = vm_set, > > > .generation = vm_generation, > > > -- > > > 2.25.1 > >