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

[Gustavo Sousa <gustavo.sousa@intel.com>]

Michal Wajdeczko <michal.wajdeczko@intel.com> writes:

> 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)

Thanks for the feedback!

After seeing Matt's feedback on patch #12, I think we will end up
dropping this MMIO intercepting stuff.

I wonder if there is value in keeping the "abort" part though, to ensure
that we don't accidentally try to read info from non-existing hardware.

If so, I guess I would just keep this patch, but modified so that we
don't need the separate xe_kunit_mmio.c file.  Also, that would be a
matter of a separate series as well, since it would be orthogonal to
this series.

Thoughts?

--
Gustavo Sousa

>
>> 
>> 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))
>>