From f138258565d18f0f9a8d07f04162c68eee997ce6 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Fri, 10 Mar 2023 16:46:09 -0800 Subject: [PATCH] KVM: selftests: Verify KVM preserves userspace writes to "durable" MSRs Assert that KVM provides "read what you wrote" semantics for all "durable" MSRs (for lack of a better name). The extra coverage is cheap from a runtime performance perspective, and verifying the behavior in the common helper avoids gratuitous copy+paste in individual tests. Note, this affects all tests that set MSRs from userspace! Link: https://lore.kernel.org/r/20230311004618.920745-13-seanjc@google.com Signed-off-by: Sean Christopherson --- tools/testing/selftests/kvm/include/x86_64/processor.h | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h index 293a9085311d..e1d65d933310 100644 --- a/tools/testing/selftests/kvm/include/x86_64/processor.h +++ b/tools/testing/selftests/kvm/include/x86_64/processor.h @@ -945,12 +945,27 @@ do { \ } \ } while (0) +/* + * Returns true if KVM should return the last written value when reading an MSR + * from userspace, e.g. the MSR isn't a command MSR, doesn't emulate state that + * is changing, etc. This is NOT an exhaustive list! The intent is to filter + * out MSRs that are not durable _and_ that a selftest wants to write. + */ +static inline bool is_durable_msr(uint32_t msr) +{ + return msr != MSR_IA32_TSC; +} + #define vcpu_set_msr(vcpu, msr, val) \ do { \ - uint64_t v = val; \ + uint64_t r, v = val; \ \ TEST_ASSERT_MSR(_vcpu_set_msr(vcpu, msr, v) == 1, \ "KVM_SET_MSRS failed on %s, value = 0x%lx", msr, #msr, v); \ + if (!is_durable_msr(msr)) \ + break; \ + r = vcpu_get_msr(vcpu, msr); \ + TEST_ASSERT_MSR(r == v, "Set %s to '0x%lx', got back '0x%lx'", msr, #msr, v, r);\ } while (0) void kvm_get_cpu_address_width(unsigned int *pa_bits, unsigned int *va_bits); -- 2.11.0