linux-kernel - Re: [PATCH 26/26] vfio/xe: Add vendor-specific vfio

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <rqgewmv4g7xsoxfez6y5g6etl7s6o7vqcqmbbmjftebdtxssvj@2uao5kmhkow2>
Date: Wed, 22 Oct 2025 11:05:12 +0200
From: Michał Winiarski <michal.winiarski@...el.com>
To: Jason Gunthorpe <jgg@...pe.ca>
CC: Alex Williamson <alex.williamson@...hat.com>, Lucas De Marchi
	<lucas.demarchi@...el.com>, Thomas Hellström
	<thomas.hellstrom@...ux.intel.com>, Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Yishai Hadas <yishaih@...dia.com>, Kevin Tian <kevin.tian@...el.com>,
	"Shameer Kolothum" <shameerali.kolothum.thodi@...wei.com>,
	<intel-xe@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
	<kvm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>, Matthew Brost
	<matthew.brost@...el.com>, Michal Wajdeczko <michal.wajdeczko@...el.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>, Joonas Lahtinen
	<joonas.lahtinen@...ux.intel.com>, Tvrtko Ursulin <tursulin@...ulin.net>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, "Lukasz
 Laguna" <lukasz.laguna@...el.com>
Subject: Re: [PATCH 26/26] vfio/xe: Add vendor-specific vfio_pci driver for
 Intel graphics

On Tue, Oct 21, 2025 at 08:03:28PM -0300, Jason Gunthorpe wrote:
> On Sat, Oct 11, 2025 at 09:38:47PM +0200, Michał Winiarski wrote:
> > +	/*
> > +	 * "STOP" handling is reused for "RUNNING_P2P", as the device doesn't have the capability to
> > +	 * selectively block p2p DMA transfers.
> > +	 * The device is not processing new workload requests when the VF is stopped, and both
> > +	 * memory and MMIO communication channels are transferred to destination (where processing
> > +	 * will be resumed).
> > +	 */
> > +	if ((cur == VFIO_DEVICE_STATE_RUNNING && new == VFIO_DEVICE_STATE_STOP) ||
> > +	    (cur == VFIO_DEVICE_STATE_RUNNING && new == VFIO_DEVICE_STATE_RUNNING_P2P)) {
> > +		ret = xe_sriov_vfio_stop(xe_vdev->pf, xe_vdev->vfid);
> 
> This comment is not right, RUNNING_P2P means the device can still
> receive P2P activity on it's BAR. Eg a GPU will still allow read/write
> to its framebuffer.
> 
> But it is not initiating any new transactions.

/*
 * "STOP" handling is reused for "RUNNING_P2P", as the device doesn't
 * have the capability to selectively block outgoing p2p DMA transfers.
 * While the device is allowing BAR accesses when the VF is stopped, it
 * is not processing any new workload requests, effectively stopping
 * any outgoing DMA transfers (not just p2p).
 * Both memory and MMIO communication channels with the workload
 * scheduling firmware are transferred to destination (where processing
 * will be resumed).
 */

Does this work better?

> 
> > +static void xe_vfio_pci_migration_init(struct vfio_device *core_vdev)
> > +{
> > +	struct xe_vfio_pci_core_device *xe_vdev =
> > +		container_of(core_vdev, struct xe_vfio_pci_core_device, core_device.vdev);
> > +	struct pci_dev *pdev = to_pci_dev(core_vdev->dev);
> > +
> > +	if (!xe_sriov_vfio_migration_supported(pdev->physfn))
> > +		return;
> > +
> > +	/* vfid starts from 1 for xe */
> > +	xe_vdev->vfid = pci_iov_vf_id(pdev) + 1;
> > +	xe_vdev->pf = pdev->physfn;
> 
> No, this has to use pci_iov_get_pf_drvdata, and this driver should
> never have a naked pf pointer flowing around.
> 
> The entire exported interface is wrongly formed:
> 
> +bool xe_sriov_vfio_migration_supported(struct pci_dev *pdev);
> +int xe_sriov_vfio_wait_flr_done(struct pci_dev *pdev, unsigned int vfid);
> +int xe_sriov_vfio_stop(struct pci_dev *pdev, unsigned int vfid);
> +int xe_sriov_vfio_run(struct pci_dev *pdev, unsigned int vfid);
> +int xe_sriov_vfio_stop_copy_enter(struct pci_dev *pdev, unsigned int vfid);
> 
> None of these should be taking in a naked pci_dev, it should all work
> on whatever type the drvdata is.

I'll change it to:

struct xe_device *xe_sriov_vfio_get_xe_device(struct pci_dev *pdev);
bool xe_sriov_vfio_migration_supported(struct xe_device *xe);
int xe_sriov_vfio_wait_flr_done(struct xe_device *xe, unsigned int vfid);
int xe_sriov_vfio_stop(struct xe_device *xe, unsigned int vfid);
int xe_sriov_vfio_run(struct xe_device *xe, unsigned int vfid);
int xe_sriov_vfio_stop_copy_enter(struct xe_device *xe, unsigned int vfid);
(...)

> 
> And this gross thing needs to go away too:
> 
> > +       if (pdev->is_virtfn && strcmp(pdev->physfn->dev.driver->name, "xe") == 0)
> > +               xe_vfio_pci_migration_init(core_vdev);

Right. With using pci_iov_get_pf_drvdata() it just goes away
automatically.

Thanks,
-Michał

> 
> Jason