From 0792c71c1c94964952339f3251818b6dcf66c19b Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 10 Jun 2025 15:57:37 -0700 Subject: [PATCH] KVM: selftests: Verify KVM disable interception (for userspace) on filter change Re-read MSR_{FS,GS}_BASE after restoring the "allow everything" userspace MSR filter to verify that KVM stops forwarding exits to userspace. This can also be used in conjunction with manual verification (e.g. printk) to ensure KVM is correctly updating the MSR bitmaps consumed by hardware. Tested-by: Dapeng Mi Tested-by: Manali Shukla Link: https://lore.kernel.org/r/20250610225737.156318-33-seanjc@google.com Signed-off-by: Sean Christopherson --- tools/testing/selftests/kvm/x86/userspace_msr_exit_test.c | 8 ++++++++ 1 file changed, 8 insertions(+) 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 32b2794b78fec..8463a99564105 100644 --- a/tools/testing/selftests/kvm/x86/userspace_msr_exit_test.c +++ b/tools/testing/selftests/kvm/x86/userspace_msr_exit_test.c @@ -343,6 +343,12 @@ static void guest_code_permission_bitmap(void) data = test_rdmsr(MSR_GS_BASE); GUEST_ASSERT(data == MSR_GS_BASE); + /* Access the MSRs again to ensure KVM has disabled interception.*/ + data = test_rdmsr(MSR_FS_BASE); + GUEST_ASSERT(data != MSR_FS_BASE); + data = test_rdmsr(MSR_GS_BASE); + GUEST_ASSERT(data != MSR_GS_BASE); + GUEST_DONE(); } @@ -682,6 +688,8 @@ KVM_ONE_VCPU_TEST(user_msr, msr_permission_bitmap, guest_code_permission_bitmap) "Expected ucall state to be UCALL_SYNC."); vm_ioctl(vm, KVM_X86_SET_MSR_FILTER, &filter_gs); run_guest_then_process_rdmsr(vcpu, MSR_GS_BASE); + + vm_ioctl(vm, KVM_X86_SET_MSR_FILTER, &filter_allow); run_guest_then_process_ucall_done(vcpu); } -- 2.47.2