Re: [PATCH v10 09/10] drm/xe/pci: Introduce PCIe Function Level Reset

["Tauro, Riana" <riana.tauro@intel.com>]

On 26-08-2026 14:31, Raag Jadav wrote:
> On Tue, Aug 25, 2026 at 12:06:32PM +0200, Laguna, Lukasz wrote:
>> On 8/21/2026 13:23, Raag Jadav wrote:
>>> With bare minimum pieces in place, we can finally introduce PCIe Function
>>> Level Reset (FLR) support which re-initializes hardware state without the
>>> need for reloading the driver from userspace. All VRAM contents are lost
>>> along with hardware state and driver takes care of recreating the required
>>> kernel bos as part of re-initialization, but user still needs to recreate
>>> user bos and reload context after PCIe FLR.
>>>
>>> Signed-off-by: Raag Jadav <raag.jadav@intel.com>
>>> Tested-by: Lukasz Laguna <lukasz.laguna@intel.com>
>>> Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
>>> ---
>>>    v2: Spell out Function Level Reset (Jani)
>>>    v5: Prevent PM ref leak for wedged device (Matthew Brost)
>>>    v6: Add PCIe FLR documentation (Daniele)
>>>    v7: Refine PCIe FLR documentation (Daniele)
>>>        Introduce xe_pci_reset_skip() helper (Lukasz)
>>>    v9: Add 'Xe' prefix to document title (Rodrigo)
>>> v10: Update documentation to include PCI Error Handling (Lukasz)
>>>        Maintain wedged reference on FLR failure (Lukasz)
>>> ---
>>>    drivers/gpu/drm/xe/xe_device_types.h |   3 +
>>>    drivers/gpu/drm/xe/xe_pci_error.c    | 128 +++++++++++++++++++++++++++
>>>    2 files changed, 131 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h
>>> index 7be3f15bf7a0..8cbb5b747710 100644
>>> --- a/drivers/gpu/drm/xe/xe_device_types.h
>>> +++ b/drivers/gpu/drm/xe/xe_device_types.h
>>> @@ -518,6 +518,9 @@ struct xe_device {
>>>    	/** @pxp: Encapsulate Protected Xe Path support */
>>>    	struct xe_pxp *pxp;
>>> +	/** @flr_prepared: Prepared for function-reset */
>>> +	bool flr_prepared;
>>> +
>>>    	/** @needs_flr_on_fini: requests function-reset on fini */
>>>    	bool needs_flr_on_fini;
>>> diff --git a/drivers/gpu/drm/xe/xe_pci_error.c b/drivers/gpu/drm/xe/xe_pci_error.c
>>> index 48466d726eae..81c4e55fae8f 100644
>>> --- a/drivers/gpu/drm/xe/xe_pci_error.c
>>> +++ b/drivers/gpu/drm/xe/xe_pci_error.c
>>> @@ -12,8 +12,55 @@
>>>    #include "xe_pm.h"
>>>    #include "xe_printk.h"
>>>    #include "xe_ras.h"
>>> +#include "xe_sriov_pf_helpers.h"
>>>    #include "xe_survivability_mode.h"
>>> +/**
>>> + * DOC: Xe PCI Error Handling
>>> + *
>>> + * Xe driver registers PCI callbacks which are called by PCI core in case of
>>> + * bus errors or resets.
>>> + *
>>> + * Currently both Function Level Reset (FLR) and bus error handling callbacks are
>>> + * supported. Both wipe the VRAM and resets the state of all the hardware units.
>>> + * Therefore, the contents of all exec queues and BOs in VRAM are lost, and the
>>> + * hardware needs a full re-initialization. The way Xe driver handles it, is
>>> + * pretty much similar to system suspend/resume flow with a few notable exceptions.
>>> + *
>>> + * Prepare phase:
>>> + *
>>> + * - Temporarily wedge the device to prevent userspace access
>>> + * - Kill exec queues which signals all fences and frees in-flight jobs
>>> + * - Stop the scheduler and all submissions to GuC
>>> + * - The fact that FLR is needed is because hardware could be in corrupted state
>>> + *   and access unreliable, so skip memory eviction due to untrustworthy VRAM
>>> + *   contents
>>> + * - Remove all memory mappings since VRAM contents will be lost
>>> + *
>>> + * Re-initialization phase:
>>> + *
>>> + * - Recreate kernel BOs due to skipped memory eviction in prepare phase
>>> + * - Restore kernel queues which were killed in prepare phase
>>> + * - Reload all uC firmwares
>>> + * - Bring up all hardware units
>>> + * - Unwedge the device to allow userspace access
>>> + *
>>> + * Since VRAM contents are lost, the user is expected to recreate user memory
>>> + * and reload context.
>>> + *
>>> + * TODO: Reuse FLR callbacks for bus error handling.
>>> + *
>>> + * Current implementation is only limited to re-initializing GT. This needs to
>>> + * be extended for a lot of components listed below.
>>> + *
>>> + * - Proper re-initialization of GSC and PXP for integrated platforms
>>> + * - SR-IOV cases which need PF and VF synchronization
>>> + * - Re-initialization of all child devices registered by Xe
>>> + * - Prepare existing xe_device_wedged() users for temporary wedging
>>> + * - MM corner cases
>>> + * - Display
>>> + */
>>> +
>>>    static void prepare_device_for_reset(struct pci_dev *pdev)
>>>    {
>>>    	struct xe_device *xe = pdev_to_xe_device(pdev);
>>> @@ -142,9 +189,90 @@ static void xe_pci_error_resume(struct pci_dev *pdev)
>>>    	xe_device_wedged_put(xe);
>>>    }
>>> +static inline bool xe_pci_reset_skip(struct xe_device *xe)
>>> +{
Add a TODO
>>> +	return !IS_DGFX(xe) || IS_SRIOV_VF(xe) || xe_sriov_pf_num_vfs(xe) || xe->info.probe_display;
>>> +}
>>> +
>>> +static void xe_pci_reset_prepare(struct pci_dev *pdev)
>>> +{
>>> +	struct xe_device *xe = pdev_to_xe_device(pdev);
>>> +	int err;
>>> +
>>> +	err = xe_pci_reset_skip(xe);
>>> +	if (err) {
>>> +		xe_err(xe, "PCIe FLR not supported\n");
Nit: Can the log be just PCIe reset
>>> +		goto wedge;
>> Looks like we always take the reference, so can't we do it at the top of
>> this function and only return here?
> Because we check for pre-existing ref below, in that case something else
> is already wrong and it's pointless to move forward. We take a local ref
> anyway because PCI core doesn't distinguish failure cases and calls
> ->reset_done() regardless, so we have to compensate for it by maintaining
> the ref across calls (which we later drop in ->reset_done()).

  If it is not supported why not just return in both function calls? Why 
proceed?

Riana

>
> Raag
>
>>> +	}
>>> +
>>> +	err = xe_device_wedged(xe);
>>> +	if (err)
>>> +		xe_err(xe, "PCIe FLR failed, device in unexpected state\n");
>>> +
>>> +wedge:
>>> +	/* Wedge the device to prevent userspace access but don't send the event yet */
>>> +	xe_device_wedged_get(xe);
>>> +	if (err)
>>> +		return;
>>> +
>>> +	/*
>>> +	 * The hardware could be in corrupted state and access unreliable, but we try to
>>> +	 * update data structures and cleanup any pending work to avoid side effects during
>>> +	 * PCIe FLR. This will be similar to system suspend flow but without eviction.
>>> +	 */
>>> +	err = xe_device_suspend(xe, true);
>>> +	if (err) {
>>> +		xe_err(xe, "Failed to prepare for PCIe FLR\n");
>>> +		return;
>>> +	}
>>> +
>>> +	xe->flr_prepared = true;
>>> +	xe_info(xe, "Prepared for PCIe FLR\n");
>>> +}
>>> +
>>> +static void xe_pci_reset_done(struct pci_dev *pdev)
>>> +{
>>> +	struct xe_device *xe = pdev_to_xe_device(pdev);
>>> +	int err;
>>> +
>>> +	err = xe_pci_reset_skip(xe);
>>> +	if (err)
>>> +		goto out;
>>> +
>>> +	if (!xe->flr_prepared)
>>> +		goto out;
>>> +
>>> +	/* Unprepare early in case we fail */
>>> +	xe->flr_prepared = false;
>>> +
>>> +	/*
>>> +	 * We already have the data structures intact, so try to re-initialize the device.
>>> +	 * This will be similar to system resume flow, except we'll also need to recreate
>>> +	 * kernel bos and restore kernel queues.
>>> +	 */
>>> +	err = xe_device_resume(xe, true);
>>> +	if (err) {
>>> +		xe_err(xe, "Re-initialization failed\n");
>>> +		goto out;
>>> +	}
>>> +
>>> +	/* Unwedge to allow userspace access */
>>> +	xe_device_wedged_put(xe);
>>> +	xe_info(xe, "Re-initialization success\n");
>>> +
>>> +	return;
>>> +out:
>>> +	/* Most likely the device is unusable and there's nothing we can do about it */
>>> +	xe_device_declare_wedged(xe);
>>> +	/* Drop local reference */
>>> +	xe_device_wedged_put(xe);
>>> +}
>>> +
>>>    const struct pci_error_handlers xe_pci_error_handlers = {
>>>    	.error_detected	= xe_pci_error_detected,
>>>    	.mmio_enabled	= xe_pci_error_mmio_enabled,
>>>    	.slot_reset	= xe_pci_error_slot_reset,
>>>    	.resume		= xe_pci_error_resume,
>>> +	.reset_prepare	= xe_pci_reset_prepare,
>>> +	.reset_done	= xe_pci_reset_done,
>>>    };