Re: [PATCH 12/12] KVM: arm64: Add selftest checking how the absence of GICv3 is handled

[Oliver Upton <oliver.upton@linux.dev>]

On Tue, Aug 20, 2024 at 11:03:49AM +0100, Marc Zyngier wrote:
> Given how tortuous and fragile the whole lack-of-GICv3 story is,
> add a selftest checking that we don't regress it.
> 
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  tools/testing/selftests/kvm/Makefile          |   1 +
>  .../selftests/kvm/aarch64/no-vgic-v3.c        | 170 ++++++++++++++++++
>  2 files changed, 171 insertions(+)
>  create mode 100644 tools/testing/selftests/kvm/aarch64/no-vgic-v3.c
> 
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 48d32c5aa3eb..f66b37acc0b0 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -163,6 +163,7 @@ TEST_GEN_PROGS_aarch64 += aarch64/vgic_init
>  TEST_GEN_PROGS_aarch64 += aarch64/vgic_irq
>  TEST_GEN_PROGS_aarch64 += aarch64/vgic_lpi_stress
>  TEST_GEN_PROGS_aarch64 += aarch64/vpmu_counter_access
> +TEST_GEN_PROGS_aarch64 += aarch64/no-vgic-v3
>  TEST_GEN_PROGS_aarch64 += access_tracking_perf_test
>  TEST_GEN_PROGS_aarch64 += arch_timer
>  TEST_GEN_PROGS_aarch64 += demand_paging_test
> diff --git a/tools/testing/selftests/kvm/aarch64/no-vgic-v3.c b/tools/testing/selftests/kvm/aarch64/no-vgic-v3.c
> new file mode 100644
> index 000000000000..27169afc94c6
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/aarch64/no-vgic-v3.c
> @@ -0,0 +1,170 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +// Check that, on a GICv3 system, not configuring GICv3 correctly
> +// results in all of the sysregs generating an UNDEF exception.
> +
> +#include <test_util.h>
> +#include <kvm_util.h>
> +#include <processor.h>
> +
> +static volatile bool handled;
> +
> +#define __check_sr_read(r)					\
> +	do {							\
> +		uint64_t val;					\
> +								\
> +		handled = false;				\
> +		dsb(sy);					\
> +		val = read_sysreg_s(SYS_ ## r);			\
> +		(void)val;					\
> +	} while(0)
> +
> +#define __check_sr_write(r)					\
> +	do {							\
> +		handled = false;				\
> +		dsb(sy);					\
> +		write_sysreg_s(0, SYS_ ## r);			\
> +		isb();						\
> +	} while(0)
> +
> +/* Fatal checks */
> +#define check_sr_read(r)					\
> +	do {							\
> +		__check_sr_read(r);				\
> +		__GUEST_ASSERT(handled, #r " no read trap");	\
> +	} while(0)
> +
> +#define check_sr_write(r)					\
> +	do {							\
> +		__check_sr_write(r);				\
> +		__GUEST_ASSERT(handled, #r " no write trap");	\
> +	} while(0)
> +
> +#define check_sr_rw(r)				\
> +	do {					\
> +		check_sr_read(r);		\
> +		check_sr_write(r);		\
> +	} while(0)
> +
> +/* Non-fatal checks */
> +#define check_sr_read_maybe(r)						\
> +	do {								\
> +		__check_sr_read(r);					\
> +		if (!handled)						\
> +			GUEST_PRINTF(#r " read not trapping (OK)\n");	\
> +	} while(0)
> +
> +#define check_sr_write_maybe(r)						\
> +	do {								\
> +		__check_sr_write(r);					\
> +		if (!handled)						\
> +			GUEST_PRINTF(#r " write not trapping (OK)\n");	\
> +	} while(0)
> +
> +static void guest_code(void)
> +{
> +	/*
> +	 * Check that we advertise that ID_AA64PFR0_EL1.GIC == 0, having
> +	 * hidden the feature at runtime without any other userspace action.
> +	 */
> +	__GUEST_ASSERT(FIELD_GET(ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_GIC),
> +				 read_sysreg(id_aa64pfr0_el1)) == 0,
> +		       "GICv3 wrongly advertised");
> +
> +	/*
> +	 * Access all GICv3 registers, and fail if we don't get an UNDEF.
> +	 * Note that we happily access all the APxRn registers without
> +	 * checking their existance, as all we want to see is a failure.
> +	 */
> +	check_sr_rw(ICC_PMR_EL1);
> +	check_sr_read(ICC_IAR0_EL1);
> +	check_sr_write(ICC_EOIR0_EL1);
> +	check_sr_rw(ICC_HPPIR0_EL1);
> +	check_sr_rw(ICC_BPR0_EL1);
> +	check_sr_rw(ICC_AP0R0_EL1);
> +	check_sr_rw(ICC_AP0R1_EL1);
> +	check_sr_rw(ICC_AP0R2_EL1);
> +	check_sr_rw(ICC_AP0R3_EL1);
> +	check_sr_rw(ICC_AP1R0_EL1);
> +	check_sr_rw(ICC_AP1R1_EL1);
> +	check_sr_rw(ICC_AP1R2_EL1);
> +	check_sr_rw(ICC_AP1R3_EL1);
> +	check_sr_write(ICC_DIR_EL1);
> +	check_sr_read(ICC_RPR_EL1);
> +	check_sr_write(ICC_SGI1R_EL1);
> +	check_sr_write(ICC_ASGI1R_EL1);
> +	check_sr_write(ICC_SGI0R_EL1);
> +	check_sr_read(ICC_IAR1_EL1);
> +	check_sr_write(ICC_EOIR1_EL1);
> +	check_sr_rw(ICC_HPPIR1_EL1);
> +	check_sr_rw(ICC_BPR1_EL1);
> +	check_sr_rw(ICC_CTLR_EL1);
> +	check_sr_rw(ICC_IGRPEN0_EL1);
> +	check_sr_rw(ICC_IGRPEN1_EL1);
> +
> +	/*
> +	 * ICC_SRE_EL1 may not be trappable, as ICC_SRE_EL2.Enable can
> +	 * be RAO/WI
> +	 */
> +	check_sr_read_maybe(ICC_SRE_EL1);
> +	check_sr_write_maybe(ICC_SRE_EL1);

In the case that a write does not UNDEF, should we check that
ICC_SRE_EL1.SRE is also RAO/WI?

-- 
Thanks,
Oliver