2022-10-13 10:18:33

by Vitaly Kuznetsov

[permalink] [raw]
Subject: [PATCH v5 0/7] KVM: x86: Hyper-V invariant TSC control feature

Changes since v4:
- s,HV_INVARIANT_TSC_EXPOSED,HV_EXPOSE_INVARIANT_TSC, [Michael]
- Add Michael's R-b to PATCH1
- Use 'KVM-only' instead of 'scattered' in PATCH2's subject [Sean, Jim]
- Do not set CPUID_8000_0007_EDX to 'NCAPINTS + 1' explicitly [Sean]
- Use the opportunity and switch to 'true'/'false' for 'msr->write'/
'msr->fault_exepected' in 'hyperv_features' test [Sean]
- Fix HVCALL_NOTIFY_LONG_SPIN_WAIT test breakage by setting
HYPERV_CPUID_ENLIGHTMENT_INFO.EBX.
- "KVM: selftests: Test that values written to Hyper-V MSRs are
preserved" patch added [Sean]

Original description:

Normally, genuine Hyper-V doesn't expose architectural invariant TSC
(CPUID.80000007H:EDX[8]) to its guests by default. A special PV MSR
(HV_X64_MSR_TSC_INVARIANT_CONTROL, 0x40000118) and corresponding CPUID
feature bit (CPUID.0x40000003.EAX[15]) were introduced. When bit 0 of the
PV MSR is set, invariant TSC bit starts to show up in CPUID. When the
feature is exposed to Hyper-V guests, reenlightenment becomes unneeded.

Note: strictly speaking, KVM doesn't have to have the feature as exposing
raw invariant TSC bit (CPUID.80000007H:EDX[8]) also seems to work for
modern Windows versions. The feature is, however, tiny and straitforward
and gives additional flexibility so why not.

Vitaly Kuznetsov (7):
x86/hyperv: Add HV_EXPOSE_INVARIANT_TSC define
KVM: x86: Add a KVM-only leaf for CPUID_8000_0007_EDX
KVM: x86: Hyper-V invariant TSC control
KVM: selftests: Rename 'msr->available' to 'msr->fault_exepected' in
hyperv_features test
KVM: selftests: Convert hyperv_features test to using
KVM_X86_CPU_FEATURE()
KVM: selftests: Test that values written to Hyper-V MSRs are preserved
KVM: selftests: Test Hyper-V invariant TSC control

arch/x86/include/asm/hyperv-tlfs.h | 3 +
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kernel/cpu/mshyperv.c | 2 +-
arch/x86/kvm/cpuid.c | 11 +-
arch/x86/kvm/hyperv.c | 19 +
arch/x86/kvm/hyperv.h | 27 ++
arch/x86/kvm/reverse_cpuid.h | 7 +
arch/x86/kvm/x86.c | 4 +-
.../selftests/kvm/include/x86_64/hyperv.h | 144 +++++---
.../selftests/kvm/include/x86_64/processor.h | 1 +
.../selftests/kvm/x86_64/hyperv_features.c | 330 +++++++++++-------
11 files changed, 366 insertions(+), 183 deletions(-)

--
2.37.3


2022-10-13 10:18:38

by Vitaly Kuznetsov

[permalink] [raw]
Subject: [PATCH v5 1/7] x86/hyperv: Add HV_EXPOSE_INVARIANT_TSC define

Avoid open coding BIT(0) of HV_X64_MSR_TSC_INVARIANT_CONTROL by adding
a dedicated define. While there's only one user at this moment, the
upcoming KVM implementation of Hyper-V Invariant TSC feature will need
to use it as well.

Reviewed-by: Michael Kelley <[email protected]>
Signed-off-by: Vitaly Kuznetsov <[email protected]>
---
arch/x86/include/asm/hyperv-tlfs.h | 3 +++
arch/x86/kernel/cpu/mshyperv.c | 2 +-
2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index 3089ec352743..196a8945bcd7 100644
--- a/arch/x86/include/asm/hyperv-tlfs.h
+++ b/arch/x86/include/asm/hyperv-tlfs.h
@@ -253,6 +253,9 @@ enum hv_isolation_type {
/* TSC invariant control */
#define HV_X64_MSR_TSC_INVARIANT_CONTROL 0x40000118

+/* HV_X64_MSR_TSC_INVARIANT_CONTROL bits */
+#define HV_EXPOSE_INVARIANT_TSC BIT_ULL(0)
+
/* Register name aliases for temporary compatibility */
#define HV_X64_MSR_STIMER0_COUNT HV_REGISTER_STIMER0_COUNT
#define HV_X64_MSR_STIMER0_CONFIG HV_REGISTER_STIMER0_CONFIG
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 831613959a92..e402923800d7 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -388,7 +388,7 @@ static void __init ms_hyperv_init_platform(void)
* setting of this MSR bit should happen before init_intel()
* is called.
*/
- wrmsrl(HV_X64_MSR_TSC_INVARIANT_CONTROL, 0x1);
+ wrmsrl(HV_X64_MSR_TSC_INVARIANT_CONTROL, HV_EXPOSE_INVARIANT_TSC);
setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
}

--
2.37.3

2022-10-13 10:18:40

by Vitaly Kuznetsov

[permalink] [raw]
Subject: [PATCH v5 7/7] KVM: selftests: Test Hyper-V invariant TSC control

Add a test for the newly introduced Hyper-V invariant TSC control feature:
- HV_X64_MSR_TSC_INVARIANT_CONTROL is not available without
HV_ACCESS_TSC_INVARIANT CPUID bit set and available with it.
- BIT(0) of HV_X64_MSR_TSC_INVARIANT_CONTROL controls the filtering of
architectural invariant TSC (CPUID.80000007H:EDX[8]) bit.

Signed-off-by: Vitaly Kuznetsov <[email protected]>
---
.../selftests/kvm/include/x86_64/hyperv.h | 3 ++
.../selftests/kvm/include/x86_64/processor.h | 1 +
.../selftests/kvm/x86_64/hyperv_features.c | 47 +++++++++++++++++++
3 files changed, 51 insertions(+)

diff --git a/tools/testing/selftests/kvm/include/x86_64/hyperv.h b/tools/testing/selftests/kvm/include/x86_64/hyperv.h
index 843748dde1ff..8368d65afbe4 100644
--- a/tools/testing/selftests/kvm/include/x86_64/hyperv.h
+++ b/tools/testing/selftests/kvm/include/x86_64/hyperv.h
@@ -232,4 +232,7 @@
/* hypercall options */
#define HV_HYPERCALL_FAST_BIT BIT(16)

+/* HV_X64_MSR_TSC_INVARIANT_CONTROL bits */
+#define HV_INVARIANT_TSC_EXPOSED BIT_ULL(0)
+
#endif /* !SELFTEST_KVM_HYPERV_H */
diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
index e8ca0d8a6a7e..39230e3add69 100644
--- a/tools/testing/selftests/kvm/include/x86_64/processor.h
+++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
@@ -128,6 +128,7 @@ struct kvm_x86_cpu_feature {
#define X86_FEATURE_GBPAGES KVM_X86_CPU_FEATURE(0x80000001, 0, EDX, 26)
#define X86_FEATURE_RDTSCP KVM_X86_CPU_FEATURE(0x80000001, 0, EDX, 27)
#define X86_FEATURE_LM KVM_X86_CPU_FEATURE(0x80000001, 0, EDX, 29)
+#define X86_FEATURE_INVTSC KVM_X86_CPU_FEATURE(0x80000007, 0, EDX, 8)
#define X86_FEATURE_RDPRU KVM_X86_CPU_FEATURE(0x80000008, 0, EBX, 4)
#define X86_FEATURE_AMD_IBPB KVM_X86_CPU_FEATURE(0x80000008, 0, EBX, 12)
#define X86_FEATURE_NPT KVM_X86_CPU_FEATURE(0x8000000A, 0, EDX, 0)
diff --git a/tools/testing/selftests/kvm/x86_64/hyperv_features.c b/tools/testing/selftests/kvm/x86_64/hyperv_features.c
index 0cfab315eb22..42fbd71c6489 100644
--- a/tools/testing/selftests/kvm/x86_64/hyperv_features.c
+++ b/tools/testing/selftests/kvm/x86_64/hyperv_features.c
@@ -82,6 +82,16 @@ static void guest_msr(struct msr_data *msr)
if (msr->write)
GUEST_ASSERT_3(msr_val == msr->write_val, msr->idx,
msr_val, msr->write_val);
+
+ /* Invariant TSC bit appears when TSC invariant control MSR is written to */
+ if (msr->idx == HV_X64_MSR_TSC_INVARIANT_CONTROL) {
+ if (!this_cpu_has(HV_ACCESS_TSC_INVARIANT))
+ GUEST_ASSERT(this_cpu_has(X86_FEATURE_INVTSC));
+ else
+ GUEST_ASSERT(this_cpu_has(X86_FEATURE_INVTSC) ==
+ !!(msr_val & HV_INVARIANT_TSC_EXPOSED));
+ }
+
done:
GUEST_DONE();
}
@@ -137,6 +147,7 @@ static void guest_test_msrs_access(void)
int stage = 0;
vm_vaddr_t msr_gva;
struct msr_data *msr;
+ bool has_invtsc = kvm_cpu_has(X86_FEATURE_INVTSC);

while (true) {
vm = vm_create_with_one_vcpu(&vcpu, guest_msr);
@@ -454,6 +465,42 @@ static void guest_test_msrs_access(void)
break;

case 44:
+ /* MSR is not available when CPUID feature bit is unset */
+ if (!has_invtsc)
+ continue;
+ msr->idx = HV_X64_MSR_TSC_INVARIANT_CONTROL;
+ msr->write = false;
+ msr->fault_expected = true;
+ break;
+ case 45:
+ /* MSR is vailable when CPUID feature bit is set */
+ if (!has_invtsc)
+ continue;
+ vcpu_set_cpuid_feature(vcpu, HV_ACCESS_TSC_INVARIANT);
+ msr->idx = HV_X64_MSR_TSC_INVARIANT_CONTROL;
+ msr->write = false;
+ msr->fault_expected = false;
+ break;
+ case 46:
+ /* Writing bits other than 0 is forbidden */
+ if (!has_invtsc)
+ continue;
+ msr->idx = HV_X64_MSR_TSC_INVARIANT_CONTROL;
+ msr->write = true;
+ msr->write_val = 0xdeadbeef;
+ msr->fault_expected = true;
+ break;
+ case 47:
+ /* Setting bit 0 enables the feature */
+ if (!has_invtsc)
+ continue;
+ msr->idx = HV_X64_MSR_TSC_INVARIANT_CONTROL;
+ msr->write = true;
+ msr->write_val = 1;
+ msr->fault_expected = false;
+ break;
+
+ default:
kvm_vm_free(vm);
return;
}
--
2.37.3

2022-10-13 10:40:17

by Vitaly Kuznetsov

[permalink] [raw]
Subject: [PATCH v5 4/7] KVM: selftests: Rename 'msr->available' to 'msr->fault_exepected' in hyperv_features test

It may not be clear what 'msr->available' means. The test actually
checks that accessing the particular MSR doesn't cause #GP, rename
the variable accordingly.

While on it, use 'true'/'false' instead of '1'/'0' for 'write'/
'fault_expected' as these are boolean.

Signed-off-by: Vitaly Kuznetsov <[email protected]>
---
.../selftests/kvm/x86_64/hyperv_features.c | 184 +++++++++---------
1 file changed, 92 insertions(+), 92 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86_64/hyperv_features.c b/tools/testing/selftests/kvm/x86_64/hyperv_features.c
index 05b32e550a80..3a93e0eb7c6e 100644
--- a/tools/testing/selftests/kvm/x86_64/hyperv_features.c
+++ b/tools/testing/selftests/kvm/x86_64/hyperv_features.c
@@ -34,7 +34,7 @@ static inline uint8_t hypercall(u64 control, vm_vaddr_t input_address,

struct msr_data {
uint32_t idx;
- bool available;
+ bool fault_expected;
bool write;
u64 write_val;
};
@@ -57,10 +57,10 @@ static void guest_msr(struct msr_data *msr)
else
vector = wrmsr_safe(msr->idx, msr->write_val);

- if (msr->available)
- GUEST_ASSERT_2(!vector, msr->idx, vector);
- else
+ if (msr->fault_expected)
GUEST_ASSERT_2(vector == GP_VECTOR, msr->idx, vector);
+ else
+ GUEST_ASSERT_2(!vector, msr->idx, vector);
GUEST_DONE();
}

@@ -153,13 +153,13 @@ static void guest_test_msrs_access(void)
* Only available when Hyper-V identification is set
*/
msr->idx = HV_X64_MSR_GUEST_OS_ID;
- msr->write = 0;
- msr->available = 0;
+ msr->write = false;
+ msr->fault_expected = true;
break;
case 1:
msr->idx = HV_X64_MSR_HYPERCALL;
- msr->write = 0;
- msr->available = 0;
+ msr->write = false;
+ msr->fault_expected = true;
break;
case 2:
feat->eax |= HV_MSR_HYPERCALL_AVAILABLE;
@@ -168,118 +168,118 @@ static void guest_test_msrs_access(void)
* HV_X64_MSR_HYPERCALL available.
*/
msr->idx = HV_X64_MSR_GUEST_OS_ID;
- msr->write = 1;
+ msr->write = true;
msr->write_val = LINUX_OS_ID;
- msr->available = 1;
+ msr->fault_expected = false;
break;
case 3:
msr->idx = HV_X64_MSR_GUEST_OS_ID;
- msr->write = 0;
- msr->available = 1;
+ msr->write = false;
+ msr->fault_expected = false;
break;
case 4:
msr->idx = HV_X64_MSR_HYPERCALL;
- msr->write = 0;
- msr->available = 1;
+ msr->write = false;
+ msr->fault_expected = false;
break;

case 5:
msr->idx = HV_X64_MSR_VP_RUNTIME;
- msr->write = 0;
- msr->available = 0;
+ msr->write = false;
+ msr->fault_expected = true;
break;
case 6:
feat->eax |= HV_MSR_VP_RUNTIME_AVAILABLE;
msr->idx = HV_X64_MSR_VP_RUNTIME;
- msr->write = 0;
- msr->available = 1;
+ msr->write = false;
+ msr->fault_expected = false;
break;
case 7:
/* Read only */
msr->idx = HV_X64_MSR_VP_RUNTIME;
- msr->write = 1;
+ msr->write = true;
msr->write_val = 1;
- msr->available = 0;
+ msr->fault_expected = true;
break;

case 8:
msr->idx = HV_X64_MSR_TIME_REF_COUNT;
- msr->write = 0;
- msr->available = 0;
+ msr->write = false;
+ msr->fault_expected = true;
break;
case 9:
feat->eax |= HV_MSR_TIME_REF_COUNT_AVAILABLE;
msr->idx = HV_X64_MSR_TIME_REF_COUNT;
- msr->write = 0;
- msr->available = 1;
+ msr->write = false;
+ msr->fault_expected = false;
break;
case 10:
/* Read only */
msr->idx = HV_X64_MSR_TIME_REF_COUNT;
- msr->write = 1;
+ msr->write = true;
msr->write_val = 1;
- msr->available = 0;
+ msr->fault_expected = true;
break;

case 11:
msr->idx = HV_X64_MSR_VP_INDEX;
- msr->write = 0;
- msr->available = 0;
+ msr->write = false;
+ msr->fault_expected = true;
break;
case 12:
feat->eax |= HV_MSR_VP_INDEX_AVAILABLE;
msr->idx = HV_X64_MSR_VP_INDEX;
- msr->write = 0;
- msr->available = 1;
+ msr->write = false;
+ msr->fault_expected = false;
break;
case 13:
/* Read only */
msr->idx = HV_X64_MSR_VP_INDEX;
- msr->write = 1;
+ msr->write = true;
msr->write_val = 1;
- msr->available = 0;
+ msr->fault_expected = true;
break;

case 14:
msr->idx = HV_X64_MSR_RESET;
- msr->write = 0;
- msr->available = 0;
+ msr->write = false;
+ msr->fault_expected = true;
break;
case 15:
feat->eax |= HV_MSR_RESET_AVAILABLE;
msr->idx = HV_X64_MSR_RESET;
- msr->write = 0;
- msr->available = 1;
+ msr->write = false;
+ msr->fault_expected = false;
break;
case 16:
msr->idx = HV_X64_MSR_RESET;
- msr->write = 1;
+ msr->write = true;
msr->write_val = 0;
- msr->available = 1;
+ msr->fault_expected = false;
break;

case 17:
msr->idx = HV_X64_MSR_REFERENCE_TSC;
- msr->write = 0;
- msr->available = 0;
+ msr->write = false;
+ msr->fault_expected = true;
break;
case 18:
feat->eax |= HV_MSR_REFERENCE_TSC_AVAILABLE;
msr->idx = HV_X64_MSR_REFERENCE_TSC;
- msr->write = 0;
- msr->available = 1;
+ msr->write = false;
+ msr->fault_expected = false;
break;
case 19:
msr->idx = HV_X64_MSR_REFERENCE_TSC;
- msr->write = 1;
+ msr->write = true;
msr->write_val = 0;
- msr->available = 1;
+ msr->fault_expected = false;
break;

case 20:
msr->idx = HV_X64_MSR_EOM;
- msr->write = 0;
- msr->available = 0;
+ msr->write = false;
+ msr->fault_expected = true;
break;
case 21:
/*
@@ -287,146 +287,146 @@ static void guest_test_msrs_access(void)
* capability enabled and guest visible CPUID bit unset.
*/
msr->idx = HV_X64_MSR_EOM;
- msr->write = 0;
- msr->available = 0;
+ msr->write = false;
+ msr->fault_expected = true;
break;
case 22:
feat->eax |= HV_MSR_SYNIC_AVAILABLE;
msr->idx = HV_X64_MSR_EOM;
- msr->write = 0;
- msr->available = 1;
+ msr->write = false;
+ msr->fault_expected = false;
break;
case 23:
msr->idx = HV_X64_MSR_EOM;
- msr->write = 1;
+ msr->write = true;
msr->write_val = 0;
- msr->available = 1;
+ msr->fault_expected = false;
break;

case 24:
msr->idx = HV_X64_MSR_STIMER0_CONFIG;
- msr->write = 0;
- msr->available = 0;
+ msr->write = false;
+ msr->fault_expected = true;
break;
case 25:
feat->eax |= HV_MSR_SYNTIMER_AVAILABLE;
msr->idx = HV_X64_MSR_STIMER0_CONFIG;
- msr->write = 0;
- msr->available = 1;
+ msr->write = false;
+ msr->fault_expected = false;
break;
case 26:
msr->idx = HV_X64_MSR_STIMER0_CONFIG;
- msr->write = 1;
+ msr->write = true;
msr->write_val = 0;
- msr->available = 1;
+ msr->fault_expected = false;
break;
case 27:
/* Direct mode test */
msr->idx = HV_X64_MSR_STIMER0_CONFIG;
- msr->write = 1;
+ msr->write = true;
msr->write_val = 1 << 12;
- msr->available = 0;
+ msr->fault_expected = true;
break;
case 28:
feat->edx |= HV_STIMER_DIRECT_MODE_AVAILABLE;
msr->idx = HV_X64_MSR_STIMER0_CONFIG;
- msr->write = 1;
+ msr->write = true;
msr->write_val = 1 << 12;
- msr->available = 1;
+ msr->fault_expected = false;
break;

case 29:
msr->idx = HV_X64_MSR_EOI;
- msr->write = 0;
- msr->available = 0;
+ msr->write = false;
+ msr->fault_expected = true;
break;
case 30:
feat->eax |= HV_MSR_APIC_ACCESS_AVAILABLE;
msr->idx = HV_X64_MSR_EOI;
- msr->write = 1;
+ msr->write = true;
msr->write_val = 1;
- msr->available = 1;
+ msr->fault_expected = false;
break;

case 31:
msr->idx = HV_X64_MSR_TSC_FREQUENCY;
- msr->write = 0;
- msr->available = 0;
+ msr->write = false;
+ msr->fault_expected = true;
break;
case 32:
feat->eax |= HV_ACCESS_FREQUENCY_MSRS;
msr->idx = HV_X64_MSR_TSC_FREQUENCY;
- msr->write = 0;
- msr->available = 1;
+ msr->write = false;
+ msr->fault_expected = false;
break;
case 33:
/* Read only */
msr->idx = HV_X64_MSR_TSC_FREQUENCY;
- msr->write = 1;
+ msr->write = true;
msr->write_val = 1;
- msr->available = 0;
+ msr->fault_expected = true;
break;

case 34:
msr->idx = HV_X64_MSR_REENLIGHTENMENT_CONTROL;
- msr->write = 0;
- msr->available = 0;
+ msr->write = false;
+ msr->fault_expected = true;
break;
case 35:
feat->eax |= HV_ACCESS_REENLIGHTENMENT;
msr->idx = HV_X64_MSR_REENLIGHTENMENT_CONTROL;
- msr->write = 0;
- msr->available = 1;
+ msr->write = false;
+ msr->fault_expected = false;
break;
case 36:
msr->idx = HV_X64_MSR_REENLIGHTENMENT_CONTROL;
- msr->write = 1;
+ msr->write = true;
msr->write_val = 1;
- msr->available = 1;
+ msr->fault_expected = false;
break;
case 37:
/* Can only write '0' */
msr->idx = HV_X64_MSR_TSC_EMULATION_STATUS;
- msr->write = 1;
+ msr->write = true;
msr->write_val = 1;
- msr->available = 0;
+ msr->fault_expected = true;
break;

case 38:
msr->idx = HV_X64_MSR_CRASH_P0;
- msr->write = 0;
- msr->available = 0;
+ msr->write = false;
+ msr->fault_expected = true;
break;
case 39:
feat->edx |= HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE;
msr->idx = HV_X64_MSR_CRASH_P0;
- msr->write = 0;
- msr->available = 1;
+ msr->write = false;
+ msr->fault_expected = false;
break;
case 40:
msr->idx = HV_X64_MSR_CRASH_P0;
- msr->write = 1;
+ msr->write = true;
msr->write_val = 1;
- msr->available = 1;
+ msr->fault_expected = false;
break;

case 41:
msr->idx = HV_X64_MSR_SYNDBG_STATUS;
- msr->write = 0;
- msr->available = 0;
+ msr->write = false;
+ msr->fault_expected = true;
break;
case 42:
feat->edx |= HV_FEATURE_DEBUG_MSRS_AVAILABLE;
dbg->eax |= HV_X64_SYNDBG_CAP_ALLOW_KERNEL_DEBUGGING;
msr->idx = HV_X64_MSR_SYNDBG_STATUS;
- msr->write = 0;
- msr->available = 1;
+ msr->write = false;
+ msr->fault_expected = false;
break;
case 43:
msr->idx = HV_X64_MSR_SYNDBG_STATUS;
- msr->write = 1;
+ msr->write = true;
msr->write_val = 0;
- msr->available = 1;
+ msr->fault_expected = false;
break;

case 44:
--
2.37.3

2022-10-13 10:47:40

by Vitaly Kuznetsov

[permalink] [raw]
Subject: [PATCH v5 6/7] KVM: selftests: Test that values written to Hyper-V MSRs are preserved

Enhance 'hyperv_features' selftest by adding a check that KVM
preserves values written to PV MSRs. Two MSRs are, however, 'special':
- HV_X64_MSR_EOI as it is a 'write-only' MSR,
- HV_X64_MSR_RESET as it always reads as '0'.
The later doesn't require any special handling right now because the
test never writes anything besides '0' to the MSR, leave a TODO node
about the fact.

Suggested-by: Sean Christopherson <[email protected]>
Signed-off-by: Vitaly Kuznetsov <[email protected]>
---
.../selftests/kvm/x86_64/hyperv_features.c | 36 ++++++++++++++-----
1 file changed, 28 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86_64/hyperv_features.c b/tools/testing/selftests/kvm/x86_64/hyperv_features.c
index d4549830c9d6..0cfab315eb22 100644
--- a/tools/testing/selftests/kvm/x86_64/hyperv_features.c
+++ b/tools/testing/selftests/kvm/x86_64/hyperv_features.c
@@ -53,22 +53,36 @@ struct hcall_data {
bool ud_expected;
};

+static bool is_write_only_msr(uint32_t msr)
+{
+ return msr == HV_X64_MSR_EOI;
+}
+
static void guest_msr(struct msr_data *msr)
{
- uint64_t ignored;
- uint8_t vector;
+ uint8_t vector = 0;
+ uint64_t msr_val = 0;

GUEST_ASSERT(msr->idx);

- if (!msr->write)
- vector = rdmsr_safe(msr->idx, &ignored);
- else
+ if (msr->write)
vector = wrmsr_safe(msr->idx, msr->write_val);

+ if (!vector && (!msr->write || !is_write_only_msr(msr->idx)))
+ vector = rdmsr_safe(msr->idx, &msr_val);
+
if (msr->fault_expected)
- GUEST_ASSERT_2(vector == GP_VECTOR, msr->idx, vector);
+ GUEST_ASSERT_3(vector == GP_VECTOR, msr->idx, vector, GP_VECTOR);
else
- GUEST_ASSERT_2(!vector, msr->idx, vector);
+ GUEST_ASSERT_3(!vector, msr->idx, vector, 0);
+
+ if (vector || is_write_only_msr(msr->idx))
+ goto done;
+
+ if (msr->write)
+ GUEST_ASSERT_3(msr_val == msr->write_val, msr->idx,
+ msr_val, msr->write_val);
+done:
GUEST_DONE();
}

@@ -258,6 +272,12 @@ static void guest_test_msrs_access(void)
case 16:
msr->idx = HV_X64_MSR_RESET;
msr->write = true;
+ /*
+ * TODO: the test only writes '0' to HV_X64_MSR_RESET
+ * at the moment, writing some other value there will
+ * trigger real vCPU reset and the code is not prepared
+ * to handle it yet.
+ */
msr->write_val = 0;
msr->fault_expected = false;
break;
@@ -452,7 +472,7 @@ static void guest_test_msrs_access(void)

switch (get_ucall(vcpu, &uc)) {
case UCALL_ABORT:
- REPORT_GUEST_ASSERT_2(uc, "MSR = %lx, vector = %lx");
+ REPORT_GUEST_ASSERT_3(uc, "MSR = %lx, arg1 = %lx, arg2 = %lx");
return;
case UCALL_DONE:
break;
--
2.37.3

2022-10-14 20:38:59

by Sean Christopherson

[permalink] [raw]
Subject: Re: [PATCH v5 0/7] KVM: x86: Hyper-V invariant TSC control feature

On Thu, Oct 13, 2022, Vitaly Kuznetsov wrote:
> Normally, genuine Hyper-V doesn't expose architectural invariant TSC
> (CPUID.80000007H:EDX[8]) to its guests by default. A special PV MSR
> (HV_X64_MSR_TSC_INVARIANT_CONTROL, 0x40000118) and corresponding CPUID
> feature bit (CPUID.0x40000003.EAX[15]) were introduced. When bit 0 of the
> PV MSR is set, invariant TSC bit starts to show up in CPUID. When the
> feature is exposed to Hyper-V guests, reenlightenment becomes unneeded.
>
> Note: strictly speaking, KVM doesn't have to have the feature as exposing
> raw invariant TSC bit (CPUID.80000007H:EDX[8]) also seems to work for
> modern Windows versions. The feature is, however, tiny and straitforward
> and gives additional flexibility so why not.
>
> Vitaly Kuznetsov (7):
> x86/hyperv: Add HV_EXPOSE_INVARIANT_TSC define
> KVM: x86: Add a KVM-only leaf for CPUID_8000_0007_EDX
> KVM: x86: Hyper-V invariant TSC control
> KVM: selftests: Rename 'msr->available' to 'msr->fault_exepected' in
> hyperv_features test
> KVM: selftests: Convert hyperv_features test to using
> KVM_X86_CPU_FEATURE()
> KVM: selftests: Test that values written to Hyper-V MSRs are preserved
> KVM: selftests: Test Hyper-V invariant TSC control

For the series, in case Paolo ends up grabbing this:

Reviewed-by: Sean Christopherson <[email protected]>

2022-11-22 16:40:58

by Vitaly Kuznetsov

[permalink] [raw]
Subject: Re: [PATCH v5 0/7] KVM: x86: Hyper-V invariant TSC control feature

Sean Christopherson <[email protected]> writes:

> On Thu, Oct 13, 2022, Vitaly Kuznetsov wrote:
>> Normally, genuine Hyper-V doesn't expose architectural invariant TSC
>> (CPUID.80000007H:EDX[8]) to its guests by default. A special PV MSR
>> (HV_X64_MSR_TSC_INVARIANT_CONTROL, 0x40000118) and corresponding CPUID
>> feature bit (CPUID.0x40000003.EAX[15]) were introduced. When bit 0 of the
>> PV MSR is set, invariant TSC bit starts to show up in CPUID. When the
>> feature is exposed to Hyper-V guests, reenlightenment becomes unneeded.
>>
>> Note: strictly speaking, KVM doesn't have to have the feature as exposing
>> raw invariant TSC bit (CPUID.80000007H:EDX[8]) also seems to work for
>> modern Windows versions. The feature is, however, tiny and straitforward
>> and gives additional flexibility so why not.
>>
>> Vitaly Kuznetsov (7):
>> x86/hyperv: Add HV_EXPOSE_INVARIANT_TSC define
>> KVM: x86: Add a KVM-only leaf for CPUID_8000_0007_EDX
>> KVM: x86: Hyper-V invariant TSC control
>> KVM: selftests: Rename 'msr->available' to 'msr->fault_exepected' in
>> hyperv_features test
>> KVM: selftests: Convert hyperv_features test to using
>> KVM_X86_CPU_FEATURE()
>> KVM: selftests: Test that values written to Hyper-V MSRs are preserved
>> KVM: selftests: Test Hyper-V invariant TSC control
>
> For the series, in case Paolo ends up grabbing this:
>
> Reviewed-by: Sean Christopherson <[email protected]>
>

I completely forgot about this one! Any chance it can still be queueed
for 6.2? Thanks!

--
Vitaly