linux-kernel - RE: [PATCH V4 03/11] vfio/pci: Prepare for dynamic interrupt context storage

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Date:   Fri, 5 May 2023 07:21:10 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     "Chatre, Reinette" <reinette.chatre@...el.com>,
        "jgg@...dia.com" <jgg@...dia.com>,
        "yishaih@...dia.com" <yishaih@...dia.com>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>
CC:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "darwi@...utronix.de" <darwi@...utronix.de>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        "Liu, Jing2" <jing2.liu@...el.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        "tom.zanussi@...ux.intel.com" <tom.zanussi@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH V4 03/11] vfio/pci: Prepare for dynamic interrupt context
 storage

> From: Chatre, Reinette <reinette.chatre@...el.com>
> Sent: Saturday, April 29, 2023 2:24 AM
> 
> Hi Kevin,
> 
> On 4/27/2023 11:33 PM, Tian, Kevin wrote:
> >> From: Chatre, Reinette <reinette.chatre@...el.com>
> >> Sent: Friday, April 28, 2023 1:36 AM
> >>
> >> @@ -55,17 +80,28 @@ static void vfio_send_intx_eventfd(void *opaque,
> >> void *unused)
> >>  {
> >>  	struct vfio_pci_core_device *vdev = opaque;
> >>
> >> -	if (likely(is_intx(vdev) && !vdev->virq_disabled))
> >> -		eventfd_signal(vdev->ctx[0].trigger, 1);
> >> +	if (likely(is_intx(vdev) && !vdev->virq_disabled)) {
> >> +		struct vfio_pci_irq_ctx *ctx;
> >> +
> >> +		ctx = vfio_irq_ctx_get(vdev, 0);
> >> +		if (!ctx)
> >> +			return;
> >
> > if this error happens it implies a kernel bug since the same check
> > has been done in vfio_intx_enable(). Then should be a WARN_ON().
> 
> Sure. Considering that if these are triggered it may result
> in many instances, so perhaps WARN_ON_ONCE()?

yes.

> 
> > ditto for other intx functions which can be called only after intx
> > is enabled.
> 
> It seems the instances in this category can be identified as the places
> where the array contents is currently used without any checks.
> 
> I am planning on the following changes:
> 

that looks good to me