linux-kernel - Re: [PATCH V6 8/9] virtio: harden vring IRQ

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Message-ID: <87sfort5fz.fsf@redhat.com>
Date:   Mon, 30 May 2022 17:18:08 +0200
From:   Cornelia Huck <cohuck@...hat.com>
To:     Jason Wang <jasowang@...hat.com>, mst@...hat.com,
        jasowang@...hat.com, virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Cc:     tglx@...utronix.de, peterz@...radead.org, paulmck@...nel.org,
        maz@...nel.org, pasic@...ux.ibm.com, eperezma@...hat.com,
        lulu@...hat.com, sgarzare@...hat.com, xuanzhuo@...ux.alibaba.com,
        Vineeth Vijayan <vneethv@...ux.ibm.com>,
        Peter Oberparleiter <oberpar@...ux.ibm.com>,
        linux-s390@...r.kernel.org
Subject: Re: [PATCH V6 8/9] virtio: harden vring IRQ

On Fri, May 27 2022, Jason Wang <jasowang@...hat.com> wrote:

> This is a rework on the previous IRQ hardening that is done for
> virtio-pci where several drawbacks were found and were reverted:
>
> 1) try to use IRQF_NO_AUTOEN which is not friendly to affinity managed IRQ
>    that is used by some device such as virtio-blk
> 2) done only for PCI transport
>
> The vq->broken is re-used in this patch for implementing the IRQ
> hardening. The vq->broken is set to true during both initialization
> and reset. And the vq->broken is set to false in
> virtio_device_ready(). Then vring_interrupt() can check and return
> when vq->broken is true. And in this case, switch to return IRQ_NONE
> to let the interrupt core aware of such invalid interrupt to prevent
> IRQ storm.
>
> The reason of using a per queue variable instead of a per device one
> is that we may need it for per queue reset hardening in the future.
>
> Note that the hardening is only done for vring interrupt since the
> config interrupt hardening is already done in commit 22b7050a024d7
> ("virtio: defer config changed notifications"). But the method that is
> used by config interrupt can't be reused by the vring interrupt
> handler because it uses spinlock to do the synchronization which is
> expensive.
>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: "Paul E. McKenney" <paulmck@...nel.org>
> Cc: Marc Zyngier <maz@...nel.org>
> Cc: Halil Pasic <pasic@...ux.ibm.com>
> Cc: Cornelia Huck <cohuck@...hat.com>
> Cc: Vineeth Vijayan <vneethv@...ux.ibm.com>
> Cc: Peter Oberparleiter <oberpar@...ux.ibm.com>
> Cc: linux-s390@...r.kernel.org
> Signed-off-by: Jason Wang <jasowang@...hat.com>
> ---
>  drivers/s390/virtio/virtio_ccw.c       |  4 ++++
>  drivers/virtio/virtio.c                | 15 ++++++++++++---
>  drivers/virtio/virtio_mmio.c           |  5 +++++
>  drivers/virtio/virtio_pci_modern_dev.c |  5 +++++
>  drivers/virtio/virtio_ring.c           | 11 +++++++----
>  include/linux/virtio_config.h          | 20 ++++++++++++++++++++
>  6 files changed, 53 insertions(+), 7 deletions(-)

Reviewed-by: Cornelia Huck <cohuck@...hat.com>