Re: [kvm-unit-tests PATCH] arm: add wfx test case

["Alex Bennée" <alex.bennee@linaro.org>]

Joey Gouly <joey.gouly@arm.com> writes:

> Hi,
>
> Few small comments.
>
> On Mon, Apr 27, 2026 at 02:00:45PM +0100, Alex Bennée wrote:
>> This is based on a similar test case I wrote for QEMU's tcg tests although
>> obviously able to take advantage of kvm-unit-tests additional plumbing for
>> dealing with the GIC and IRQs.
>> 
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> ---
>>  arm/Makefile.arm64        |   1 +
>>  lib/arm64/asm/processor.h |   7 ++
>>  lib/arm64/asm/sysreg.h    |   3 +
>>  arm/wfx.c                 | 137 ++++++++++++++++++++++++++++++++++++++
>>  arm/unittests.cfg         |   5 ++
>>  5 files changed, 153 insertions(+)
>>  create mode 100644 arm/wfx.c
>> 
>> diff --git a/arm/Makefile.arm64 b/arm/Makefile.arm64
>> index a40c830d..52b3f35d 100644
>> --- a/arm/Makefile.arm64
>> +++ b/arm/Makefile.arm64
>> @@ -64,6 +64,7 @@ tests += $(TEST_DIR)/cache.$(exe)
>>  tests += $(TEST_DIR)/debug.$(exe)
>>  tests += $(TEST_DIR)/fpu.$(exe)
>>  tests += $(TEST_DIR)/mte.$(exe)
>> +tests += $(TEST_DIR)/wfx.$(exe)
>>  
>>  include $(SRCDIR)/$(TEST_DIR)/Makefile.common
>>  
>> diff --git a/lib/arm64/asm/processor.h b/lib/arm64/asm/processor.h
>> index 32ddc1b3..2104036d 100644
>> --- a/lib/arm64/asm/processor.h
>> +++ b/lib/arm64/asm/processor.h
>> @@ -173,5 +173,12 @@ static inline bool system_supports_rndr(void)
>>  	return ((id_aa64isar0_el1 >> ID_AA64ISAR0_EL1_RNDR_SHIFT) & 0xf) != 0;
>>  }
>>  
>> +static inline bool system_supports_wfxt(void)
>> +{
>> +	u64 id_aa64isar2_el1 = read_sysreg_s(ID_AA64ISAR2_EL1);
>> +
>> +	return ((id_aa64isar2_el1 >> ID_AA64ISAR2_EL1_WFxT_SHIFT) & 0xf) != 0;
>> +}
>> +
>>  #endif /* !__ASSEMBLER__ */
>>  #endif /* _ASMARM64_PROCESSOR_H_ */
>> diff --git a/lib/arm64/asm/sysreg.h b/lib/arm64/asm/sysreg.h
>> index f2d05018..cb96a649 100644
>> --- a/lib/arm64/asm/sysreg.h
>> +++ b/lib/arm64/asm/sysreg.h
>> @@ -77,6 +77,9 @@ asm(
>>  #define ID_AA64ISAR0_EL1_RNDR_SHIFT	60
>>  #define ID_AA64PFR1_EL1_MTE_SHIFT	8
>>  
>> +#define ID_AA64ISAR2_EL1		sys_reg(3, 0, 0, 6, 2)
>> +#define ID_AA64ISAR2_EL1_WFxT_SHIFT	0
>> +
>>  #define ID_AA64MMFR0_EL1_FGT_SHIFT	56
>>  #define ID_AA64MMFR0_EL1_FGT_FGT2	0x2
>>  
>> diff --git a/arm/wfx.c b/arm/wfx.c
>> new file mode 100644
>> index 00000000..912e50e6
>> --- /dev/null
>> +++ b/arm/wfx.c
>> @@ -0,0 +1,137 @@
>> +/*
>> + * WFX Instructions Test (WFI, WFE, WFIT, WFET)
>> + *
>> + * Copyright (c) 2026 Linaro Ltd
>> + *
>> + * SPDX-License-Identifier: GPL-2.0-or-later
>> + */
>> +
>> +#include <libcflat.h>
>> +#include <asm/processor.h>
>> +#include <asm/gic.h>
>> +#include <asm/timer.h>
>> +#include <asm/io.h>
>> +
>> +#define TIMEOUT 200000
>
> Instead of a hardcoded TIMEOUT, what about something similar to arm/timer.c:
>
> 	u64 time_10ms = read_sysreg(cntfrq_el0) / 100;

ok

>
>> +
>> +#define sev() asm volatile("sev" : : : "memory")
>> +#define sevl() asm volatile("sevl" : : : "memory")
>> +#define wfi() asm volatile("wfi" : : : "memory")
>> +#define wfe() asm volatile("wfe" : : : "memory")
>> +
>> +#define wfit(reg) \
>> +	asm volatile(".arch armv8.7-a\n\twfit %0" : : "r" (reg) : "memory")
>> +#define wfet(reg) \
>> +	asm volatile(".arch armv8.7-a\n\twfet %0" : : "r" (reg) : "memory")
>> +
>> +static void timer_handler(struct pt_regs *regs)
>> +{
>> +	/* Disable timer to stop IRQ from re-firing */
>> +	write_sysreg(0, cntv_ctl_el0);
>> +}
>> +
>> +static bool check_elapsed(uint64_t start, uint64_t threshold, const char *test, bool more)
>> +{
>> +	uint64_t end = read_sysreg(cntvct_el0);
>> +	uint64_t elapsed = end - start;
>> +	bool pass = more ? elapsed >= threshold : elapsed <= threshold;
>> +
>> +	report(pass, "%s (%ld ticks)", test, elapsed);
>> +
>> +	if (!pass) {
>> +		report_info("%s %s", test, more ? "woke too early" : "slept despite SEV");
>> +	}
>> +	return pass;
>> +}
>> +
>> +static void test_wfi(void)
>> +{
>> +	uint64_t start;
>> +
>> +	report_info("Testing WFI...");
>> +
>> +	start = read_sysreg(cntvct_el0);
>> +	write_sysreg(TIMEOUT, cntv_tval_el0);
>> +	write_sysreg(1, cntv_ctl_el0); /* Enable timer, no mask */
>> +	isb();
>> +
>> +	local_irq_enable();
>> +	wfi();
>> +	local_irq_disable();
>> +
>> +	check_elapsed(start, TIMEOUT, "WFI", true);
>> +}
>> +
>> +static void test_wfe(void)
>> +{
>> +	uint64_t start;
>> +
>
> I think a comment here would be good, just to say it's testing that a wfe
> doesn't sleep for a 'long' period with no pending events, or something like
> that?

ok

>
>> +	report_info("Testing WFE/SEV...");
>> +	sev();
>> +	start = read_sysreg(cntvct_el0);
>> +	wfe();
>> +	check_elapsed(start, TIMEOUT, "WFE/SEV", false);
>> +
>> +	report_info("Testing WFE/SEVL...");
>> +	sevl();
>> +	start = read_sysreg(cntvct_el0);
>> +	wfe();
>> +	check_elapsed(start, TIMEOUT, "WFE/SEVL", false);
>> +}
>> +
>> +static void test_wfit(void)
>> +{
>> +	uint64_t start, timeout;
>> +
>> +	report_info("Testing WFIT...");
>> +	start = read_sysreg(cntvct_el0);
>> +	timeout = start + TIMEOUT;
>> +	wfit(timeout);
>> +	check_elapsed(start, TIMEOUT, "WFIT", true);
>> +}
>> +
>> +static void test_wfet(void)
>> +{
>> +	uint64_t start, timeout;
>> +
>> +	report_info("Testing WFET...");
>> +	/* Ensure no pending events */
>> +	sev();
>
> Could this just be sevl here? Not that it really matters.

it could be - ideally I would extend the test case to work with -smp so
we can properly exercise that code path as well.

>
>> +	wfe();
>> +
>> +	start = read_sysreg(cntvct_el0);
>> +	timeout = start + TIMEOUT;
>> +	wfet(timeout);
>> +	check_elapsed(start, TIMEOUT, "WFET", true);
>> +}
>> +
>> +int main(void)
>> +{
>> +
>> +	if (gic_init() < 0) {
>> +		report_abort("GIC init failed");
>> +		return 1;
>> +	}
>> +
>> +	/* Install timer handler for WFI wake-up */
>> +	install_irq_handler(EL1H_IRQ, timer_handler);
>> +	gic_enable_defaults();
>> +
>> +	/* Enable Virtual Timer PPI */
>> +	gic_irq_set_clr_enable(27, true);
>
> Instead of hardcoding 27 here, you can use:
>
> 	u32 irq = current_level() == CurrentEL_EL1 ? TIMER_VTIMER_IRQ : TIMER_HVTIMER_IRQ;                                                                     
> 	gic_irq_set_clr_enable(irq, true);
>
> Which also allows the test to run at EL2.

sounds good.

>
>> +
>> +	report_prefix_push("WFx");
>> +	test_wfi();
>> +	test_wfe();
>> +	report_prefix_pop();
>> +
>> +	if (system_supports_wfxt()) {
>> +		report_prefix_push("WFxT");
>> +		test_wfit();
>> +		test_wfet();
>> +	} else {
>> +		report_skip("WFxT instructions not supported");
>> +	}
>> +
>> +	return report_summary();
>> +}
>> diff --git a/arm/unittests.cfg b/arm/unittests.cfg
>> index 12fc4468..7adf96f2 100644
>> --- a/arm/unittests.cfg
>> +++ b/arm/unittests.cfg
>> @@ -339,3 +339,8 @@ groups = mte
>>  test_args = asymm
>>  qemu_params = -machine mte=on
>>  arch = arm64
>> +
>> +[wfx]
>> +file = wfx.flat
>> +groups = wfx
>> +arch = arm64
>
> Thanks,
> Joey

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro