[PATCH 06/13] KVM: arm64: selftests: Alias EL1 registers to EL2 counterparts

Oliver Upton
2025-09-17T21:21:34Z

FEAT_VHE has the somewhat nice property of implicitly redirecting EL1
register aliases to their corresponding EL2 representations when E2H=1.
Unfortunately, there's no such abstraction for userspace and EL2
registers are always accessed by their canonical encoding.

Introduce a helper that applies EL2 redirections to sysregs and use
aggressive inlining to catch misuse at compile time. Go a little past
the architectural definition for ease of use for test authors (e.g. the
stack pointer).

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
.../selftests/kvm/arm64/vpmu_counter_access.c | 4 +-
.../selftests/kvm/include/arm64/processor.h | 54 +++++++++++++++++++
.../testing/selftests/kvm/include/kvm_util.h | 3 ++
.../selftests/kvm/lib/arm64/processor.c | 19 +++----
4 files changed, 69 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c b/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c
index 4a7e8e85a1b8..36a3a8b4e0b5 100644
--- a/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c
+++ b/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c
@@ -517,7 +517,7 @@ static void run_access_test(uint64_t pmcr_n)
vcpu = vpmu_vm.vcpu;

/* Save the initial sp to restore them later to run the guest again */
- sp = vcpu_get_reg(vcpu, ARM64_CORE_REG(sp_el1));
+ sp = vcpu_get_reg(vcpu, ctxt_reg_alias(vcpu, SYS_SP_EL1));

run_vcpu(vcpu, pmcr_n);

@@ -529,7 +529,7 @@ static void run_access_test(uint64_t pmcr_n)
init.features[0] |= (1 << KVM_ARM_VCPU_PMU_V3);
aarch64_vcpu_setup(vcpu, &init);
vcpu_init_descriptor_tables(vcpu);
- vcpu_set_reg(vcpu, ARM64_CORE_REG(sp_el1), sp);
+ vcpu_set_reg(vcpu, ctxt_reg_alias(vcpu, SYS_SP_EL1), sp);
vcpu_set_reg(vcpu, ARM64_CORE_REG(regs.pc), (uint64_t)guest_code);

run_vcpu(vcpu, pmcr_n);
diff --git a/tools/testing/selftests/kvm/include/arm64/processor.h b/tools/testing/selftests/kvm/include/arm64/processor.h
index 8c066ba1deb5..5a4b29c1b965 100644
--- a/tools/testing/selftests/kvm/include/arm64/processor.h
+++ b/tools/testing/selftests/kvm/include/arm64/processor.h
@@ -303,4 +303,58 @@ void wfi(void);
void test_wants_mte(void);
void test_disable_default_vgic(void);

+static bool vcpu_has_el2(struct kvm_vcpu *vcpu)
+{
+ return vcpu->init.features[0] & BIT(KVM_ARM_VCPU_HAS_EL2);
+}
+
+#define MAPPED_EL2_SYSREG(el2, el1) \
+ case SYS_##el1: \
+ if (vcpu_has_el2(vcpu)) \
+ alias = SYS_##el2; \
+ break
+
+
+static __always_inline u64 ctxt_reg_alias(struct kvm_vcpu *vcpu, u32 encoding)
+{
+ u32 alias = encoding;
+
+ BUILD_BUG_ON(!__builtin_constant_p(encoding));
+
+ switch (encoding) {
+ MAPPED_EL2_SYSREG(SCTLR_EL2, SCTLR_EL1);
+ MAPPED_EL2_SYSREG(CPTR_EL2, CPACR_EL1);
+ MAPPED_EL2_SYSREG(TTBR0_EL2, TTBR0_EL1);
+ MAPPED_EL2_SYSREG(TTBR1_EL2, TTBR1_EL1);
+ MAPPED_EL2_SYSREG(TCR_EL2, TCR_EL1);
+ MAPPED_EL2_SYSREG(VBAR_EL2, VBAR_EL1);
+ MAPPED_EL2_SYSREG(AFSR0_EL2, AFSR0_EL1);
+ MAPPED_EL2_SYSREG(AFSR1_EL2, AFSR1_EL1);
+ MAPPED_EL2_SYSREG(ESR_EL2, ESR_EL1);
+ MAPPED_EL2_SYSREG(FAR_EL2, FAR_EL1);
+ MAPPED_EL2_SYSREG(MAIR_EL2, MAIR_EL1);
+ MAPPED_EL2_SYSREG(TCR2_EL2, TCR2_EL1);
+ MAPPED_EL2_SYSREG(PIR_EL2, PIR_EL1);
+ MAPPED_EL2_SYSREG(PIRE0_EL2, PIRE0_EL1);
+ MAPPED_EL2_SYSREG(POR_EL2, POR_EL1);
+ MAPPED_EL2_SYSREG(AMAIR_EL2, AMAIR_EL1);
+ MAPPED_EL2_SYSREG(ELR_EL2, ELR_EL1);
+ MAPPED_EL2_SYSREG(SPSR_EL2, SPSR_EL1);
+ MAPPED_EL2_SYSREG(ZCR_EL2, ZCR_EL1);
+ MAPPED_EL2_SYSREG(CONTEXTIDR_EL2, CONTEXTIDR_EL1);
+ MAPPED_EL2_SYSREG(SCTLR2_EL2, SCTLR2_EL1);
+ MAPPED_EL2_SYSREG(CNTHCTL_EL2, CNTKCTL_EL1);
+ case SYS_SP_EL1:
+ if (!vcpu_has_el2(vcpu))
+ return ARM64_CORE_REG(sp_el1);
+
+ alias = SYS_SP_EL2;
+ break;
+ default:
+ BUILD_BUG();
+ }
+
+ return KVM_ARM64_SYS_REG(alias);
+}
+
#endif /* SELFTEST_KVM_PROCESSOR_H */
diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 3ab1fffbc3f2..11b6c5aa3f12 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -63,6 +63,9 @@ struct kvm_vcpu {
struct kvm_run *run;
#ifdef __x86_64__
struct kvm_cpuid2 *cpuid;
+#endif
+#ifdef __aarch64__
+ struct kvm_vcpu_init init;
#endif
struct kvm_binary_stats stats;
struct kvm_dirty_gfn *dirty_gfns;
diff --git a/tools/testing/selftests/kvm/lib/arm64/processor.c b/tools/testing/selftests/kvm/lib/arm64/processor.c
index de77d9a7e0cd..311660a9f655 100644
--- a/tools/testing/selftests/kvm/lib/arm64/processor.c
+++ b/tools/testing/selftests/kvm/lib/arm64/processor.c
@@ -283,15 +283,16 @@ void aarch64_vcpu_setup(struct kvm_vcpu *vcpu, struct kvm_vcpu_init *init)
}

vcpu_ioctl(vcpu, KVM_ARM_VCPU_INIT, init);
+ vcpu->init = *init;

/*
* Enable FP/ASIMD to avoid trapping when accessing Q0-Q15
* registers, which the variable argument list macros do.
*/
- vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_CPACR_EL1), 3 << 20);
+ vcpu_set_reg(vcpu, ctxt_reg_alias(vcpu, SYS_CPACR_EL1), 3 << 20);

- sctlr_el1 = vcpu_get_reg(vcpu, KVM_ARM64_SYS_REG(SYS_SCTLR_EL1));
- tcr_el1 = vcpu_get_reg(vcpu, KVM_ARM64_SYS_REG(SYS_TCR_EL1));
+ sctlr_el1 = vcpu_get_reg(vcpu, ctxt_reg_alias(vcpu, SYS_SCTLR_EL1));
+ tcr_el1 = vcpu_get_reg(vcpu, ctxt_reg_alias(vcpu, SYS_TCR_EL1));

/* Configure base granule size */
switch (vm->mode) {
@@ -358,10 +359,10 @@ void aarch64_vcpu_setup(struct kvm_vcpu *vcpu, struct kvm_vcpu_init *init)
if (use_lpa2_pte_format(vm))
tcr_el1 |= TCR_DS;

- vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_SCTLR_EL1), sctlr_el1);
- vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_TCR_EL1), tcr_el1);
- vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_MAIR_EL1), DEFAULT_MAIR_EL1);
- vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_TTBR0_EL1), ttbr0_el1);
+ vcpu_set_reg(vcpu, ctxt_reg_alias(vcpu, SYS_SCTLR_EL1), sctlr_el1);
+ vcpu_set_reg(vcpu, ctxt_reg_alias(vcpu, SYS_TCR_EL1), tcr_el1);
+ vcpu_set_reg(vcpu, ctxt_reg_alias(vcpu, SYS_MAIR_EL1), DEFAULT_MAIR_EL1);
+ vcpu_set_reg(vcpu, ctxt_reg_alias(vcpu, SYS_TTBR0_EL1), ttbr0_el1);
vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_TPIDR_EL1), vcpu->id);
}

@@ -396,7 +397,7 @@ static struct kvm_vcpu *__aarch64_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id,

aarch64_vcpu_setup(vcpu, init);

- vcpu_set_reg(vcpu, ARM64_CORE_REG(sp_el1), stack_vaddr + stack_size);
+ vcpu_set_reg(vcpu, ctxt_reg_alias(vcpu, SYS_SP_EL1), stack_vaddr + stack_size);
return vcpu;
}

@@ -466,7 +467,7 @@ void vcpu_init_descriptor_tables(struct kvm_vcpu *vcpu)
{
extern char vectors;

- vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_VBAR_EL1), (uint64_t)&vectors);
+ vcpu_set_reg(vcpu, ctxt_reg_alias(vcpu, SYS_VBAR_EL1), (uint64_t)&vectors);
}

void route_exception(struct ex_regs *regs, int vector)
--
2.47.3