linux-kernel - Re: [PATCH 15/17] vfio/pci: Let enable and disable of interrupt types use same signature

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Message-ID: <20240206150341.798bb9fe.alex.williamson@redhat.com>
Date: Tue, 6 Feb 2024 15:03:41 -0700
From: Alex Williamson <alex.williamson@...hat.com>
To: Reinette Chatre <reinette.chatre@...el.com>
Cc: <jgg@...dia.com>, <yishaih@...dia.com>,
 <shameerali.kolothum.thodi@...wei.com>, <kevin.tian@...el.com>,
 <kvm@...r.kernel.org>, <dave.jiang@...el.com>, <ashok.raj@...el.com>,
 <linux-kernel@...r.kernel.org>, <patches@...ts.linux.dev>
Subject: Re: [PATCH 15/17] vfio/pci: Let enable and disable of interrupt
 types use same signature

On Tue, 6 Feb 2024 13:46:37 -0800
Reinette Chatre <reinette.chatre@...el.com> wrote:

> Hi Alex,
> 
> On 2/5/2024 2:35 PM, Alex Williamson wrote:
> > On Thu,  1 Feb 2024 20:57:09 -0800
> > Reinette Chatre <reinette.chatre@...el.com> wrote:  
> 
> ..
> 
> >> @@ -715,13 +724,13 @@ static int vfio_pci_set_intx_trigger(struct vfio_pci_core_device *vdev,
> >>  		if (is_intx(vdev))
> >>  			return vfio_irq_set_block(vdev, start, count, fds, index);
> >>  
> >> -		ret = vfio_intx_enable(vdev);
> >> +		ret = vfio_intx_enable(vdev, start, count, index);  
> > 
> > Please trace what happens when a user calls SET_IRQS to setup a trigger
> > eventfd with start = 0, count = 1, followed by any other combination of
> > start and count values once is_intx() is true.  vfio_intx_enable()
> > cannot be the only place we bounds check the user, all of the INTx
> > callbacks should be an error or nop if vector != 0.  Thanks,
> >   
> 
> Thank you very much for catching this. I plan to add the vector
> check to the device_name() and request_interrupt() callbacks. I do
> not think it is necessary to add the vector check to disable() since
> it does not operate on a range and from what I can tell it depends on
> a successful enable() that already contains the vector check. Similar,
> free_interrupt() requires a successful request_interrupt() (that will
> have vector check in next version).
> send_eventfd() requires a valid interrupt context that is only
> possible if enable() or request_interrupt() succeeded.

Sounds reasonable.

> If user space creates an eventfd with start = 0 and count = 1
> and then attempts to trigger the eventfd using another combination then
> the changes in this series will result in a nop while the current
> implementation will result in -EINVAL. Is this acceptable?

I think by nop, you mean the ioctl returns success.  Was the call a
success?  Thanks,

Alex