Re: [PATCH v4 9/9] drm/xe/pci: Introduce PCIe FLR

[Matthew Brost <matthew.brost@intel.com>]

On Sat, Mar 28, 2026 at 02:06:20AM +0530, Raag Jadav wrote:
> With bare minimum pieces in place, we can finally introduce PCIe Function
> Level Reset (FLR) handling 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>
> ---
> v2: Spell out Function Level Reset (Jani)
> ---
>  drivers/gpu/drm/xe/Makefile     |   1 +
>  drivers/gpu/drm/xe/xe_pci.c     |   1 +
>  drivers/gpu/drm/xe/xe_pci.h     |   2 +
>  drivers/gpu/drm/xe/xe_pci_err.c | 151 ++++++++++++++++++++++++++++++++
>  4 files changed, 155 insertions(+)
>  create mode 100644 drivers/gpu/drm/xe/xe_pci_err.c
> 
> diff --git a/drivers/gpu/drm/xe/Makefile b/drivers/gpu/drm/xe/Makefile
> index dab979287a96..996b43680f84 100644
> --- a/drivers/gpu/drm/xe/Makefile
> +++ b/drivers/gpu/drm/xe/Makefile
> @@ -100,6 +100,7 @@ xe-y += xe_bb.o \
>  	xe_page_reclaim.o \
>  	xe_pat.o \
>  	xe_pci.o \
> +	xe_pci_err.o \
>  	xe_pci_rebar.o \
>  	xe_pcode.o \
>  	xe_pm.o \
> diff --git a/drivers/gpu/drm/xe/xe_pci.c b/drivers/gpu/drm/xe/xe_pci.c
> index 01673d2b2464..f252ac3ea82c 100644
> --- a/drivers/gpu/drm/xe/xe_pci.c
> +++ b/drivers/gpu/drm/xe/xe_pci.c
> @@ -1324,6 +1324,7 @@ static struct pci_driver xe_pci_driver = {
>  #ifdef CONFIG_PM_SLEEP
>  	.driver.pm = &xe_pm_ops,
>  #endif
> +	.err_handler = &xe_pci_err_handlers,
>  };
>  
>  /**
> diff --git a/drivers/gpu/drm/xe/xe_pci.h b/drivers/gpu/drm/xe/xe_pci.h
> index 11bcc5fe2c5b..85e85e8508c3 100644
> --- a/drivers/gpu/drm/xe/xe_pci.h
> +++ b/drivers/gpu/drm/xe/xe_pci.h
> @@ -8,6 +8,8 @@
>  
>  struct pci_dev;
>  
> +extern const struct pci_error_handlers xe_pci_err_handlers;
> +
>  int xe_register_pci_driver(void);
>  void xe_unregister_pci_driver(void);
>  struct xe_device *xe_pci_to_pf_device(struct pci_dev *pdev);
> diff --git a/drivers/gpu/drm/xe/xe_pci_err.c b/drivers/gpu/drm/xe/xe_pci_err.c
> new file mode 100644
> index 000000000000..b6ae1d6d85f6
> --- /dev/null
> +++ b/drivers/gpu/drm/xe/xe_pci_err.c
> @@ -0,0 +1,151 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright © 2026 Intel Corporation
> + */
> +
> +#include "xe_bo_evict.h"
> +#include "xe_device.h"
> +#include "xe_gt.h"
> +#include "xe_gt_idle.h"
> +#include "xe_i2c.h"
> +#include "xe_irq.h"
> +#include "xe_late_bind_fw.h"
> +#include "xe_pci.h"
> +#include "xe_pcode.h"
> +#include "xe_printk.h"
> +#include "xe_pxp.h"
> +#include "xe_wa.h"
> +
> +static int xe_flr_prepare(struct xe_device *xe)
> +{
> +	struct xe_gt *gt;
> +	int err;
> +	u8 id;
> +
> +	err = xe_pxp_pm_suspend(xe->pxp);
> +	if (err)
> +		return err;
> +
> +	xe_late_bind_wait_for_worker_completion(&xe->late_bind);
> +
> +	xe_irq_disable(xe);
> +
> +	for_each_gt(gt, xe, id)
> +		xe_gt_flr_prepare(gt);
> +
> +	// TODO: Drop all user bos
> +	unmap_mapping_range(xe->drm.anon_inode->i_mapping, 0, 0, 1);
> +	xe_bo_pci_dev_remove_pinned(xe);
> +
> +	return 0;
> +}
> +
> +static int xe_flr_done(struct xe_device *xe)
> +{
> +	struct xe_tile *tile;
> +	struct xe_gt *gt;
> +	int err;
> +	u8 id;
> +
> +	for_each_gt(gt, xe, id)
> +		xe_gt_idle_disable_c6(gt);
> +
> +	for_each_tile(tile, xe, id)
> +		xe_wa_apply_tile_workarounds(tile);
> +
> +	err = xe_pcode_ready(xe, true);
> +	if (err)
> +		return err;
> +
> +	xe_device_assert_lmem_ready(xe);
> +
> +	err = xe_bo_restore_map(xe);
> +	if (err)
> +		return err;
> +
> +	for_each_gt(gt, xe, id) {
> +		err = xe_gt_flr_done(gt);
> +		if (err)
> +			return err;
> +	}
> +
> +	xe_i2c_pm_resume(xe, true);
> +
> +	xe_irq_resume(xe);
> +
> +	for_each_gt(gt, xe, id) {
> +		err = xe_gt_resume(gt);
> +		if (err)
> +			return err;
> +	}
> +
> +	xe_pxp_pm_resume(xe->pxp);
> +
> +	xe_late_bind_fw_load(&xe->late_bind);
> +
> +	return 0;
> +}
> +
> +static void xe_pci_reset_prepare(struct pci_dev *pdev)
> +{
> +	struct xe_device *xe = pdev_to_xe_device(pdev);
> +
> +	/* TODO: Extend support as a follow-up */
> +	if (!IS_DGFX(xe) || IS_SRIOV_VF(xe) || pci_num_vf(pdev) || xe->info.probe_display) {
> +		xe_err(xe, "PCIe FLR not supported\n");
> +		return;
> +	}
> +
> +	/* Wedge the device to prevent userspace access but don't send the event yet */
> +	atomic_set(&xe->wedged.flag, 1);
> +
> +	/*
> +	 * 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 xe_pm_suspend() flow but without migration.
> +	 */
> +	if (xe_flr_prepare(xe)) {
> +		xe_err(xe, "Failed to prepare for PCIe FLR\n");
> +		return;
> +	}
> +
> +	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);
> +
> +	/* TODO: Extend support as a follow-up */
> +	if (!IS_DGFX(xe) || IS_SRIOV_VF(xe) || pci_num_vf(pdev) || xe->info.probe_display)
> +		return;
> +
> +	if (!xe_device_wedged(xe)) {
> +		xe_err(xe, "Device in unexpected state, re-initialization aborted\n");
> +		return;
> +	}
> +
> +	/*
> +	 * We already have the data structures intact, so try to re-initialize the device.
> +	 * This will be similar to xe_pm_resume() flow, except we'll also need to recreate
> +	 * all VRAM contents.
> +	 */
> +	if (xe_flr_done(xe)) {
> +		xe_err(xe, "Re-initialization failed\n");
> +		return;
> +	}
> +
> +	/* Unwedge to allow userspace access */
> +	atomic_set(&xe->wedged.flag, 0);

I think this will leak a PM ref which we take wedge the device. I just
fixed a recalim bug here related to this [1], so this is fresh in my
mind.

What I think you want do this is in xe_pci_reset_prepare()...

xe->wedged.pm_ref = !!atomic_xchg(&xe->wedged.flag, 1);

Then in xe_pci_reset_done()...

if (xe->wedged.pm_ref) {
	xe_pm_runtime_put(xe);
	xe->wedged.pm_ref = false;
}

Or you change the structure in [1] mess with 'xe->wedged.pm_ref',
multiple ways to do this.

Matt

[1] https://patchwork.freedesktop.org/patch/714622/?series=163948&rev=1

> +
> +	xe_info(xe, "Re-initialization success\n");
> +}
> +
> +/*
> + * PCIe Function Level Reset (FLR) support only.
> + * TODO: Add PCIe error handlers using similar flow.
> + */
> +const struct pci_error_handlers xe_pci_err_handlers = {
> +	.reset_prepare = xe_pci_reset_prepare,
> +	.reset_done = xe_pci_reset_done,
> +};
> -- 
> 2.43.0
>