Re: [PATCH 05/12] drm/xe/kunit: Abort test if MMIO operation is attempted

[Michal Wajdeczko <michal.wajdeczko@intel.com>]

On 1/16/2026 11:12 PM, Gustavo Sousa wrote:
> Regular Xe KUnit tests (i.e. not the live ones) are usually run in
> User-Mode Linux and do not have access to the real hardware and, as
> such, should not attempt to do MMIO operations. If some test ends up
> exercising a path that contains MMIO operations, the test should be
> rewritten in a way that the MMIO is skipped or simulated (e.g. via a
> static stub).
> 
> Let's make sure to abort the test if MMIO is attempted on non-live
> tests.  Before aborting, use drm_WARN() to cause a stack trace to be
> logged as a debug aid to the developer.

maybe cleaner solution would be first to add to all xe_mmio functions:

	KUNIT_STATIC_STUB_REDIRECT

and then (in separate patch) activate "abort" stubs in xe_pci_fake_device_init,
similar to what we do with read_gmdid & xe_info_probe_tile_count

if any test would like to intercept some mmio read/writes it will just provide and activate its own stub
and such usage will be no different than any other use of stubs

this will allow to drop patch 6 which introduces (IMO unnecessary) another layer
(where test should stub another test function instead of the real function)

> 
> Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
> ---
>  drivers/gpu/drm/xe/tests/Makefile        |  1 +
>  drivers/gpu/drm/xe/tests/xe_kunit_mmio.c | 35 ++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/xe/tests/xe_kunit_mmio.h | 27 ++++++++++++++++++++++++
>  drivers/gpu/drm/xe/xe_mmio.c             |  9 ++++++++
>  4 files changed, 72 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/tests/Makefile b/drivers/gpu/drm/xe/tests/Makefile
> index 0e3408f4952c..8f3a594449c8 100644
> --- a/drivers/gpu/drm/xe/tests/Makefile
> +++ b/drivers/gpu/drm/xe/tests/Makefile
> @@ -8,6 +8,7 @@ xe_live_test-y = xe_live_test_mod.o
>  obj-$(CONFIG_DRM_XE_KUNIT_TEST) += xe_test.o
>  xe_test-y = xe_test_mod.o \
>  	xe_args_test.o \
> +	xe_kunit_mmio.o \
>  	xe_pci_test.o \
>  	xe_rtp_test.o \
>  	xe_wa_test.o
> diff --git a/drivers/gpu/drm/xe/tests/xe_kunit_mmio.c b/drivers/gpu/drm/xe/tests/xe_kunit_mmio.c
> new file mode 100644
> index 000000000000..debf8bd3f9dd
> --- /dev/null
> +++ b/drivers/gpu/drm/xe/tests/xe_kunit_mmio.c
> @@ -0,0 +1,35 @@
> +// SPDX-License-Identifier: GPL-2.0 AND MIT
> +/*
> + * Copyright © 2026 Intel Corporation
> + */
> +
> +#include <kunit/test.h>
> +#include <kunit/test-bug.h>
> +
> +#include <drm/drm_print.h>
> +
> +#include "tests/xe_kunit_helpers.h"
> +#include "tests/xe_kunit_mmio.h"
> +#include "xe_device_types.h"
> +
> +/**
> + * xe_kunit_mmio_abort_if_not_live_test - Abort test execution if not in a live test.
> + * @mmio: MMIO target
> + * @reg: Register on which an MMIO operation is about to be performed
> + *
> + * This function must be called from xe_mmio functions that perform MMIO
> + * operations on the hardware.  If the current process is a kunit test and it is
> + * not a live test, it will cause a warn and abort the test; otherwise it does
> + * nothing.
> + */
> +void xe_kunit_mmio_abort_if_not_live_test(struct xe_mmio *mmio, struct xe_reg reg)
> +{
> +	struct xe_device *xe = tile_to_xe(mmio->tile);
> +	struct kunit *test = kunit_get_current_test();
> +
> +	if (!test || xe_kunit_is_live_test(test))
> +		return;
> +
> +	drm_WARN(&xe->drm, true, "MMIO function called on reg 0x%x\n", reg.addr);
> +	KUNIT_FAIL_AND_ABORT(test, "MMIO function called on reg 0x%x\n", reg.addr);
> +}
> diff --git a/drivers/gpu/drm/xe/tests/xe_kunit_mmio.h b/drivers/gpu/drm/xe/tests/xe_kunit_mmio.h
> new file mode 100644
> index 000000000000..d46ac2b82969
> --- /dev/null
> +++ b/drivers/gpu/drm/xe/tests/xe_kunit_mmio.h
> @@ -0,0 +1,27 @@
> +/* SPDX-License-Identifier: GPL-2.0 AND MIT */
> +/*
> + * Copyright © 2026 Intel Corporation
> + */
> +
> +#ifndef _XE_KUNIT_MMIO_H_
> +#define _XE_KUNIT_MMIO_H_
> +
> +#include <linux/types.h>
> +
> +#include "regs/xe_reg_defs.h"
> +
> +struct xe_mmio;
> +
> +#if IS_ENABLED(CONFIG_DRM_XE_KUNIT_TEST)
> +
> +void xe_kunit_mmio_abort_if_not_live_test(struct xe_mmio *mmio, struct xe_reg reg);
> +
> +#else
> +
> +static void xe_kunit_mmio_abort_if_not_live_test(struct xe_mmio *mmio, struct xe_reg reg)
> +{
> +}
> +
> +#endif
> +
> +#endif
> diff --git a/drivers/gpu/drm/xe/xe_mmio.c b/drivers/gpu/drm/xe/xe_mmio.c
> index bcb6674b7dac..0f9a1d5453df 100644
> --- a/drivers/gpu/drm/xe/xe_mmio.c
> +++ b/drivers/gpu/drm/xe/xe_mmio.c
> @@ -14,6 +14,7 @@
>  #include <drm/drm_print.h>
>  
>  #include "regs/xe_bars.h"
> +#include "tests/xe_kunit_mmio.h"
>  #include "xe_device.h"
>  #include "xe_gt_sriov_vf.h"
>  #include "xe_sriov.h"
> @@ -146,6 +147,8 @@ u8 xe_mmio_read8(struct xe_mmio *mmio, struct xe_reg reg)
>  	u32 addr = xe_mmio_adjusted_addr(mmio, reg.addr);
>  	u8 val;
>  
> +	xe_kunit_mmio_abort_if_not_live_test(mmio, reg);
> +
>  	mmio_flush_pending_writes(mmio);
>  
>  	val = readb(mmio->regs + addr);
> @@ -159,6 +162,8 @@ u16 xe_mmio_read16(struct xe_mmio *mmio, struct xe_reg reg)
>  	u32 addr = xe_mmio_adjusted_addr(mmio, reg.addr);
>  	u16 val;
>  
> +	xe_kunit_mmio_abort_if_not_live_test(mmio, reg);
> +
>  	mmio_flush_pending_writes(mmio);
>  
>  	val = readw(mmio->regs + addr);
> @@ -171,6 +176,8 @@ void xe_mmio_write32(struct xe_mmio *mmio, struct xe_reg reg, u32 val)
>  {
>  	u32 addr = xe_mmio_adjusted_addr(mmio, reg.addr);
>  
> +	xe_kunit_mmio_abort_if_not_live_test(mmio, reg);
> +
>  	trace_xe_reg_rw(mmio, true, addr, val, sizeof(val));
>  
>  	if (!reg.vf && IS_SRIOV_VF(mmio->tile->xe))
> @@ -185,6 +192,8 @@ u32 xe_mmio_read32(struct xe_mmio *mmio, struct xe_reg reg)
>  	u32 addr = xe_mmio_adjusted_addr(mmio, reg.addr);
>  	u32 val;
>  
> +	xe_kunit_mmio_abort_if_not_live_test(mmio, reg);
> +
>  	mmio_flush_pending_writes(mmio);
>  
>  	if (!reg.vf && IS_SRIOV_VF(mmio->tile->xe))
>