linux-kernel - RE: [PATCH] vfio/cdx: add support for CDX bus

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Date:   Thu, 13 Apr 2023 13:05:35 +0000
From:   "Gupta, Nipun" <Nipun.Gupta@....com>
To:     Jason Gunthorpe <jgg@...pe.ca>
CC:     "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "git (AMD-Xilinx)" <git@....com>,
        "Anand, Harpreet" <harpreet.anand@....com>,
        "Simek, Michal" <michal.simek@....com>,
        "Agarwal, Nikhil" <nikhil.agarwal@....com>,
        "Jansen Van Vuuren, Pieter" <pieter.jansen-van-vuuren@....com>,
        "okaya@...nel.org" <okaya@...nel.org>
Subject: RE: [PATCH] vfio/cdx: add support for CDX bus



> -----Original Message-----
> From: Gupta, Nipun
> Sent: Friday, April 7, 2023 10:35 AM
> To: Jason Gunthorpe <jgg@...pe.ca>
> Cc: alex.williamson@...hat.com; linux-kernel@...r.kernel.org;
> kvm@...r.kernel.org; git (AMD-Xilinx) <git@....com>; Anand, Harpreet
> <harpreet.anand@....com>; Simek, Michal <michal.simek@....com>;
> Agarwal, Nikhil <nikhil.agarwal@....com>; Jansen Van Vuuren, Pieter
> <pieter.jansen-van-vuuren@....com>; okaya@...nel.org
> Subject: Re: [PATCH] vfio/cdx: add support for CDX bus
> 

<snip>

> 
> >
> >> +static void vfio_cdx_close_device(struct vfio_device *core_vdev)
> >> +{
> >> +     struct vfio_cdx_device *vdev =
> >> +             container_of(core_vdev, struct vfio_cdx_device, vdev);
> >> +     int ret;
> >> +
> >> +     vfio_cdx_regions_cleanup(vdev);
> >> +
> >> +     /* reset the device before cleaning up the interrupts */
> >> +     ret = vfio_cdx_reset_device(vdev);
> >> +     if (WARN_ON(ret))
> >> +             dev_warn(core_vdev->dev,
> >> +                      "VFIO_CDX: reset device has failed (%d)\n", ret);
> >
> > This is pretty problematic.. if the reset can fail the device is
> > returned to the system in an unknown state and it seems pretty likely
> > that it can be a way to attack the kernel.
> 
> We will update the code to disable the device in case of failures.

We double checked with firmware/hardware team, when driver sends CDX
device reset command to firmware, it actually quiesce and then reset the device.
So, the device remains disabled in case of failures.

Regards,
Nipun