From b9635930f0a73c1ef7b465121896c3fb2e3b77cd Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 2 Nov 2022 11:46:52 -0700 Subject: [PATCH] KVM: selftests: Provide error code as a KVM_ASM_SAFE() output Provide the error code on a fault in KVM_ASM_SAFE(), e.g. to allow tests to assert that #PF generates the correct error code without needing to manually install a #PF handler. Use r10 as the scratch register for the error code, as it's already clobbered by the asm blob (loaded with the RIP of the to-be-executed instruction). Deliberately load the output "error_code" even in the non-faulting path so that error_code is always initialized with deterministic data (the aforementioned RIP), i.e to ensure a selftest won't end up with uninitialized consumption regardless of how KVM_ASM_SAFE() is used. Don't clear r10 in the non-faulting case and instead load error code with the RIP (see above). The error code is valid if and only if an exception occurs, and '0' isn't necessarily a better "invalid" value, e.g. '0' could result in false passes for a buggy test. Signed-off-by: Sean Christopherson Signed-off-by: David Matlack Link: https://lore.kernel.org/r/20221102184654.282799-9-dmatlack@google.com --- .../selftests/kvm/include/x86_64/processor.h | 39 +++++++++++++++------- tools/testing/selftests/kvm/lib/x86_64/processor.c | 1 + .../testing/selftests/kvm/x86_64/hyperv_features.c | 3 +- 3 files changed, 30 insertions(+), 13 deletions(-) diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h index 6f4c727..6093d0d 100644 --- a/tools/testing/selftests/kvm/include/x86_64/processor.h +++ b/tools/testing/selftests/kvm/include/x86_64/processor.h @@ -786,6 +786,7 @@ void vm_install_exception_handler(struct kvm_vm *vm, int vector, * * REGISTER OUTPUTS: * r9 = exception vector (non-zero) + * r10 = error code */ #define KVM_ASM_SAFE(insn) \ "mov $" __stringify(KVM_EXCEPTION_MAGIC) ", %%r9\n\t" \ @@ -794,29 +795,43 @@ void vm_install_exception_handler(struct kvm_vm *vm, int vector, "1: " insn "\n\t" \ "xor %%r9, %%r9\n\t" \ "2:\n\t" \ - "mov %%r9b, %[vector]\n\t" + "mov %%r9b, %[vector]\n\t" \ + "mov %%r10, %[error_code]\n\t" -#define KVM_ASM_SAFE_OUTPUTS(v) [vector] "=qm"(v) +#define KVM_ASM_SAFE_OUTPUTS(v, ec) [vector] "=qm"(v), [error_code] "=rm"(ec) #define KVM_ASM_SAFE_CLOBBERS "r9", "r10", "r11" -#define kvm_asm_safe(insn, inputs...) \ -({ \ - uint8_t vector; \ - \ - asm volatile(KVM_ASM_SAFE(insn) \ - : KVM_ASM_SAFE_OUTPUTS(vector) \ - : inputs \ - : KVM_ASM_SAFE_CLOBBERS); \ - vector; \ +#define kvm_asm_safe(insn, inputs...) \ +({ \ + uint64_t ign_error_code; \ + uint8_t vector; \ + \ + asm volatile(KVM_ASM_SAFE(insn) \ + : KVM_ASM_SAFE_OUTPUTS(vector, ign_error_code) \ + : inputs \ + : KVM_ASM_SAFE_CLOBBERS); \ + vector; \ +}) + +#define kvm_asm_safe_ec(insn, error_code, inputs...) \ +({ \ + uint8_t vector; \ + \ + asm volatile(KVM_ASM_SAFE(insn) \ + : KVM_ASM_SAFE_OUTPUTS(vector, error_code) \ + : inputs \ + : KVM_ASM_SAFE_CLOBBERS); \ + vector; \ }) static inline uint8_t rdmsr_safe(uint32_t msr, uint64_t *val) { + uint64_t error_code; uint8_t vector; uint32_t a, d; asm volatile(KVM_ASM_SAFE("rdmsr") - : "=a"(a), "=d"(d), KVM_ASM_SAFE_OUTPUTS(vector) + : "=a"(a), "=d"(d), KVM_ASM_SAFE_OUTPUTS(vector, error_code) : "c"(msr) : KVM_ASM_SAFE_CLOBBERS); diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c index 9995761..4623874 100644 --- a/tools/testing/selftests/kvm/lib/x86_64/processor.c +++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c @@ -1068,6 +1068,7 @@ static bool kvm_fixup_exception(struct ex_regs *regs) regs->rip = regs->r11; regs->r9 = regs->vector; + regs->r10 = regs->error_code; return true; } diff --git a/tools/testing/selftests/kvm/x86_64/hyperv_features.c b/tools/testing/selftests/kvm/x86_64/hyperv_features.c index 05b32e5..2b6d455 100644 --- a/tools/testing/selftests/kvm/x86_64/hyperv_features.c +++ b/tools/testing/selftests/kvm/x86_64/hyperv_features.c @@ -18,6 +18,7 @@ static inline uint8_t hypercall(u64 control, vm_vaddr_t input_address, vm_vaddr_t output_address, uint64_t *hv_status) { + uint64_t error_code; uint8_t vector; /* Note both the hypercall and the "asm safe" clobber r9-r11. */ @@ -25,7 +26,7 @@ static inline uint8_t hypercall(u64 control, vm_vaddr_t input_address, KVM_ASM_SAFE("vmcall") : "=a" (*hv_status), "+c" (control), "+d" (input_address), - KVM_ASM_SAFE_OUTPUTS(vector) + KVM_ASM_SAFE_OUTPUTS(vector, error_code) : [output_address] "r"(output_address), "a" (-EFAULT) : "cc", "memory", "r8", KVM_ASM_SAFE_CLOBBERS); -- 2.7.4