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

Marc Zyngier
2024-08-21T11:17:13Z

On Wed, 21 Aug 2024 01:10:23 +0100,
Oliver Upton <oliver.upton@linux.dev> wrote:
>
> 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?

Ah, not a bad idea. I'll add that.

Thanks,

M.

--
Without deviation from the norm, progress is not possible.