From 70e477d996c88d3915d0a870bada29ecf55e45fc Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Thu, 3 Feb 2022 11:46:17 +0100 Subject: KVM: selftests: nVMX: Add enlightened MSR-Bitmap selftest Introduce a test for enlightened MSR-Bitmap feature (Hyper-V on KVM): - Intercept access to MSR_FS_BASE in L1 and check that this works with enlightened MSR-Bitmap disabled. - Enabled enlightened MSR-Bitmap and check that the intercept still works as expected. - Intercept access to MSR_GS_BASE but don't clear the corresponding bit from 'hv_clean_fields', KVM is supposed to skip updating MSR-Bitmap02 and thus the consequent access to the MSR from L2 will not get intercepted. - Finally, clear the corresponding bit from 'hv_clean_fields' and check that access to MSR_GS_BASE is now intercepted. The test works with the assumption, that access to MSR_FS_BASE/MSR_GS_BASE is not intercepted for L1. If this ever becomes not true the test will fail as nested_vmx_exit_handled_msr() always checks L1's MSR-Bitmap for L2 irrespective of 'hv_clean_fields'. The behavior is correct as enlightened MSR-Bitmap feature is just an optimization, KVM is not obliged to ignore updates when the corresponding bit in 'hv_clean_fields' stays clear. Signed-off-by: Vitaly Kuznetsov Message-Id: <20220203104620.277031-4-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini --- tools/testing/selftests/kvm/x86_64/evmcs_test.c | 59 +++++++++++++++++++++++++ 1 file changed, 59 insertions(+) (limited to 'tools/testing/selftests/kvm/x86_64/evmcs_test.c') diff --git a/tools/testing/selftests/kvm/x86_64/evmcs_test.c b/tools/testing/selftests/kvm/x86_64/evmcs_test.c index 655104051819..d12e043aa2ee 100644 --- a/tools/testing/selftests/kvm/x86_64/evmcs_test.c +++ b/tools/testing/selftests/kvm/x86_64/evmcs_test.c @@ -10,6 +10,7 @@ #include #include #include +#include #include "test_util.h" @@ -32,6 +33,22 @@ static void guest_nmi_handler(struct ex_regs *regs) { } +/* Exits to L1 destroy GRPs! */ +static inline void rdmsr_fs_base(void) +{ + __asm__ __volatile__ ("mov $0xc0000100, %%rcx; rdmsr" : : : + "rax", "rbx", "rcx", "rdx", + "rsi", "rdi", "r8", "r9", "r10", "r11", "r12", + "r13", "r14", "r15"); +} +static inline void rdmsr_gs_base(void) +{ + __asm__ __volatile__ ("mov $0xc0000101, %%rcx; rdmsr" : : : + "rax", "rbx", "rcx", "rdx", + "rsi", "rdi", "r8", "r9", "r10", "r11", "r12", + "r13", "r14", "r15"); +} + void l2_guest_code(void) { GUEST_SYNC(7); @@ -41,6 +58,15 @@ void l2_guest_code(void) /* Forced exit to L1 upon restore */ GUEST_SYNC(9); + vmcall(); + + /* MSR-Bitmap tests */ + rdmsr_fs_base(); /* intercepted */ + rdmsr_fs_base(); /* intercepted */ + rdmsr_gs_base(); /* not intercepted */ + vmcall(); + rdmsr_gs_base(); /* intercepted */ + /* Done, exit to L1 and never come back. */ vmcall(); } @@ -91,6 +117,39 @@ void guest_code(struct vmx_pages *vmx_pages) GUEST_SYNC(10); + GUEST_ASSERT(vmreadz(VM_EXIT_REASON) == EXIT_REASON_VMCALL); + current_evmcs->guest_rip += 3; /* vmcall */ + + /* Intercept RDMSR 0xc0000100 */ + vmwrite(CPU_BASED_VM_EXEC_CONTROL, vmreadz(CPU_BASED_VM_EXEC_CONTROL) | + CPU_BASED_USE_MSR_BITMAPS); + set_bit(MSR_FS_BASE & 0x1fff, vmx_pages->msr + 0x400); + GUEST_ASSERT(!vmresume()); + GUEST_ASSERT(vmreadz(VM_EXIT_REASON) == EXIT_REASON_MSR_READ); + current_evmcs->guest_rip += 2; /* rdmsr */ + + /* Enable enlightened MSR bitmap */ + current_evmcs->hv_enlightenments_control.msr_bitmap = 1; + GUEST_ASSERT(!vmresume()); + GUEST_ASSERT(vmreadz(VM_EXIT_REASON) == EXIT_REASON_MSR_READ); + current_evmcs->guest_rip += 2; /* rdmsr */ + + /* Intercept RDMSR 0xc0000101 without telling KVM about it */ + set_bit(MSR_GS_BASE & 0x1fff, vmx_pages->msr + 0x400); + /* Make sure HV_VMX_ENLIGHTENED_CLEAN_FIELD_MSR_BITMAP is set */ + current_evmcs->hv_clean_fields |= HV_VMX_ENLIGHTENED_CLEAN_FIELD_MSR_BITMAP; + GUEST_ASSERT(!vmresume()); + /* Make sure we don't see EXIT_REASON_MSR_READ here so eMSR bitmap works */ + GUEST_ASSERT(vmreadz(VM_EXIT_REASON) == EXIT_REASON_VMCALL); + current_evmcs->guest_rip += 3; /* vmcall */ + + /* Now tell KVM we've changed MSR-Bitmap */ + current_evmcs->hv_clean_fields &= ~HV_VMX_ENLIGHTENED_CLEAN_FIELD_MSR_BITMAP; + GUEST_ASSERT(!vmresume()); + GUEST_ASSERT(vmreadz(VM_EXIT_REASON) == EXIT_REASON_MSR_READ); + current_evmcs->guest_rip += 2; /* rdmsr */ + + GUEST_ASSERT(!vmresume()); GUEST_ASSERT(vmreadz(VM_EXIT_REASON) == EXIT_REASON_VMCALL); GUEST_SYNC(11); -- cgit v1.2.3-59-g8ed1b