The msr_filter_deny test covers the FILTER and UNKNOWN MSR exit reasons, but nothing exercises KVM_MSR_EXIT_REASON_INVAL.
Have the guest write a non-canonical value to FS_BASE and verify that the write exits to userspace with KVM_MSR_EXIT_REASON_INVAL along with the attempted value. FS_BASE writes are passed through to hardware, i.e. a plain WRMSR takes #GP directly without exiting, so use forced emulation to route the write through KVM. Signed-off-by: Tharit Tangkijwanichakul <[email protected]> --- v2: - Use a write of non-canonical to FS_BASE value instead of reserved EFER bit 63 because writing non-canonical can't become valid without massive architectural changes unlike EFER reserved bit (suggested by Sean). Tested on Intel Core i5-10210U (VMX). Not tested on AMD. --- .../kvm/x86/userspace_msr_exit_test.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/kvm/x86/userspace_msr_exit_test.c b/tools/testing/selftests/kvm/x86/userspace_msr_exit_test.c index 2808ce727e5f..40b084cba2c0 100644 --- a/tools/testing/selftests/kvm/x86/userspace_msr_exit_test.c +++ b/tools/testing/selftests/kvm/x86/userspace_msr_exit_test.c @@ -309,6 +309,14 @@ static void guest_msr_calls(bool trapped) /* Invalid MSR, should always be handled by user space exit */ GUEST_ASSERT(rdmsr(0xdeadbeef) == 0xdeadbeef); wrmsr(0xdeadbeef, 0x1234); + + /* + * Writing a non-canonical value to FS_BASE is rejected by KVM, but + * FS_BASE writes are passed through to hardware, so force emulation + * to route the write through KVM and get an INVAL exit. + */ + if (is_forced_emulation_enabled) + test_em_wrmsr(MSR_FS_BASE, NONCANONICAL); } static void guest_code_filter_deny(void) @@ -627,6 +635,13 @@ static void handle_wrmsr(struct kvm_run *run) TEST_ASSERT(run->msr.reason == KVM_MSR_EXIT_REASON_UNKNOWN, "deadbeef trap w/o inval fault"); } + + if (run->msr.index == MSR_FS_BASE) { + TEST_ASSERT(run->msr.data == NONCANONICAL, + "MSR_FS_BASE data is not NONCANONICAL"); + TEST_ASSERT(run->msr.reason == KVM_MSR_EXIT_REASON_INVAL, + "MSR_FS_BASE trap w/o inval fault"); + } } KVM_ONE_VCPU_TEST(user_msr, msr_filter_deny, guest_code_filter_deny) @@ -667,7 +682,9 @@ KVM_ONE_VCPU_TEST(user_msr, msr_filter_deny, guest_code_filter_deny) done: TEST_ASSERT(msr_reads == 4, "Handled 4 rdmsr in user space"); - TEST_ASSERT(msr_writes == 3, "Handled 3 wrmsr in user space"); + TEST_ASSERT(msr_writes == (is_forced_emulation_enabled ? 5 : 3), + "Handled %u wrmsr in user space, expected %u", + msr_writes, is_forced_emulation_enabled ? 5 : 3); } KVM_ONE_VCPU_TEST(user_msr, msr_permission_bitmap, guest_code_permission_bitmap) -- 2.53.0
