[PATCH 0/5] KVM: selftests: Fix clocksource requirements in tests

[PATCH 0/5] KVM: selftests: Fix clocksource requirements in tests

[Vitaly Kuznetsov]

It was discovered that 'hyperv_clock' fails miserably when the system is
using an unsupported (by KVM) clocksource, e.g. 'kvm-clock'. The root cause
of the failure is that 'hyperv_clock' doesn't actually check which clocksource
is currently in use. Other tests (kvm_clock_test, vmx_nested_tsc_scaling_test)
have the required check but each test does it on its own.

Generalize clocksource checking infrastructure, make all three clocksource
dependent tests run with 'tsc' and 'hyperv_clocksource_tsc_page', and skip
gracefully when run in an unsupported configuration.

The last patch of the series is a loosely related minor nitpick for KVM
code itself.

Vitaly Kuznetsov (5):
  KVM: selftests: Generalize check_clocksource() from kvm_clock_test
  KVM: selftests: Use generic sys_clocksource_is_tsc() in
    vmx_nested_tsc_scaling_test
  KVM: selftests: Run clocksource dependent tests with
    hyperv_clocksource_tsc_page too
  KVM: selftests: Make hyperv_clock require TSC based system clocksource
  KVM: x86: Make gtod_is_based_on_tsc() return 'bool'

 arch/x86/kvm/x86.c                            |  2 +-
 .../testing/selftests/kvm/include/test_util.h |  2 +
 .../selftests/kvm/include/x86_64/processor.h  |  2 +
 tools/testing/selftests/kvm/lib/test_util.c   | 25 ++++++++++++
 .../selftests/kvm/lib/x86_64/processor.c      | 15 ++++++++
 .../selftests/kvm/x86_64/hyperv_clock.c       |  1 +
 .../selftests/kvm/x86_64/kvm_clock_test.c     | 38 +------------------
 .../kvm/x86_64/vmx_nested_tsc_scaling_test.c  | 19 +---------
 8 files changed, 48 insertions(+), 56 deletions(-)


base-commit: 7f26fea9bc085290e3731501f4f8fc5b82b9d615
-- 
2.43.0

[PATCH 1/5] KVM: selftests: Generalize check_clocksource() from kvm_clock_test

[Vitaly Kuznetsov]

Several existing x86 selftests need to check that the underlying system
clocksource is TSC or based on TSC but every test implements its own
check. As a first step towards unification, extract check_clocksource()
from kvm_clock_test and split it into two functions: arch-neutral
'sys_get_cur_clocksource()' and x86-specific 'sys_clocksource_is_tsc()'.
Fix a couple of pre-existing issues in kvm_clock_test: memory leakage in
check_clocksource() and using TEST_ASSERT() instead of TEST_REQUIRE().
The change also makes the test fail when system clocksource can't be read
from sysfs.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 .../testing/selftests/kvm/include/test_util.h |  2 +
 .../selftests/kvm/include/x86_64/processor.h  |  2 +
 tools/testing/selftests/kvm/lib/test_util.c   | 25 ++++++++++++
 .../selftests/kvm/lib/x86_64/processor.c      | 13 +++++++
 .../selftests/kvm/x86_64/kvm_clock_test.c     | 38 +------------------
 5 files changed, 43 insertions(+), 37 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
index 71a41fa924b7..50a5e31ba8da 100644
--- a/tools/testing/selftests/kvm/include/test_util.h
+++ b/tools/testing/selftests/kvm/include/test_util.h
@@ -195,4 +195,6 @@ __printf(3, 4) int guest_snprintf(char *buf, int n, const char *fmt, ...);
 
 char *strdup_printf(const char *fmt, ...) __attribute__((format(printf, 1, 2), nonnull(1)));
 
+char *sys_get_cur_clocksource(void);
+
 #endif /* SELFTEST_KVM_TEST_UTIL_H */
diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
index a84863503fcb..01eec72e0d3e 100644
--- a/tools/testing/selftests/kvm/include/x86_64/processor.h
+++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
@@ -1271,4 +1271,6 @@ void virt_map_level(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
 #define PFERR_GUEST_PAGE_MASK	BIT_ULL(PFERR_GUEST_PAGE_BIT)
 #define PFERR_IMPLICIT_ACCESS	BIT_ULL(PFERR_IMPLICIT_ACCESS_BIT)
 
+bool sys_clocksource_is_tsc(void);
+
 #endif /* SELFTEST_KVM_PROCESSOR_H */
diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
index 5d7f28b02d73..b8cb20cf61e9 100644
--- a/tools/testing/selftests/kvm/lib/test_util.c
+++ b/tools/testing/selftests/kvm/lib/test_util.c
@@ -392,3 +392,28 @@ char *strdup_printf(const char *fmt, ...)
 
 	return str;
 }
+
+#define CLOCKSOURCE_PATH "/sys/devices/system/clocksource/clocksource0/current_clocksource"
+
+char *sys_get_cur_clocksource(void)
+{
+	char *clk_name;
+	struct stat st;
+	FILE *fp;
+
+	fp = fopen(CLOCKSOURCE_PATH, "r");
+	TEST_ASSERT(fp, "failed to open clocksource file, errno: %d", errno);
+
+	TEST_ASSERT(!fstat(fileno(fp), &st), "failed to stat clocksource file, errno: %d",
+		    errno);
+
+	clk_name = malloc(st.st_size);
+	TEST_ASSERT(clk_name, "failed to allocate buffer to read file\n");
+
+	TEST_ASSERT(fgets(clk_name, st.st_size, fp), "failed to read clocksource file: %d",
+		    ferror(fp));
+
+	fclose(fp);
+
+	return clk_name;
+}
diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index d8288374078e..b0c64667803d 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -1299,3 +1299,16 @@ void kvm_selftest_arch_init(void)
 	host_cpu_is_intel = this_cpu_is_intel();
 	host_cpu_is_amd = this_cpu_is_amd();
 }
+
+bool sys_clocksource_is_tsc(void)
+{
+	char *clk_name = sys_get_cur_clocksource();
+	bool ret = false;
+
+	if (!strcmp(clk_name, "tsc\n"))
+		ret = true;
+
+	free(clk_name);
+
+	return ret;
+}
diff --git a/tools/testing/selftests/kvm/x86_64/kvm_clock_test.c b/tools/testing/selftests/kvm/x86_64/kvm_clock_test.c
index 1778704360a6..9deee8556b5c 100644
--- a/tools/testing/selftests/kvm/x86_64/kvm_clock_test.c
+++ b/tools/testing/selftests/kvm/x86_64/kvm_clock_test.c
@@ -132,42 +132,6 @@ static void enter_guest(struct kvm_vcpu *vcpu)
 	}
 }
 
-#define CLOCKSOURCE_PATH "/sys/devices/system/clocksource/clocksource0/current_clocksource"
-
-static void check_clocksource(void)
-{
-	char *clk_name;
-	struct stat st;
-	FILE *fp;
-
-	fp = fopen(CLOCKSOURCE_PATH, "r");
-	if (!fp) {
-		pr_info("failed to open clocksource file: %d; assuming TSC.\n",
-			errno);
-		return;
-	}
-
-	if (fstat(fileno(fp), &st)) {
-		pr_info("failed to stat clocksource file: %d; assuming TSC.\n",
-			errno);
-		goto out;
-	}
-
-	clk_name = malloc(st.st_size);
-	TEST_ASSERT(clk_name, "failed to allocate buffer to read file\n");
-
-	if (!fgets(clk_name, st.st_size, fp)) {
-		pr_info("failed to read clocksource file: %d; assuming TSC.\n",
-			ferror(fp));
-		goto out;
-	}
-
-	TEST_ASSERT(!strncmp(clk_name, "tsc\n", st.st_size),
-		    "clocksource not supported: %s", clk_name);
-out:
-	fclose(fp);
-}
-
 int main(void)
 {
 	struct kvm_vcpu *vcpu;
@@ -179,7 +143,7 @@ int main(void)
 	flags = kvm_check_cap(KVM_CAP_ADJUST_CLOCK);
 	TEST_REQUIRE(flags & KVM_CLOCK_REALTIME);
 
-	check_clocksource();
+	TEST_REQUIRE(sys_clocksource_is_tsc());
 
 	vm = vm_create_with_one_vcpu(&vcpu, guest_main);
 
-- 
2.43.0

Re: [PATCH 1/5] KVM: selftests: Generalize check_clocksource() from kvm_clock_test

[Sean Christopherson]

On Tue, Jan 09, 2024, Vitaly Kuznetsov wrote:
> +bool sys_clocksource_is_tsc(void)
> +{
> +	char *clk_name = sys_get_cur_clocksource();
> +	bool ret = false;
> +
> +	if (!strcmp(clk_name, "tsc\n"))
> +		ret = true;

This can more simply be:

	bool ret = !strcmp(clk_name, "tsc\n");

and then

	bool ret = !strcmp(clk_name, "tsc\n") ||
		   !strcmp(clk_name, "hyperv_clocksource_tsc_page\n");

when the Hyper-V variant comes along.  I'll fixup when applying unless you
violently disagree.

[PATCH 2/5] KVM: selftests: Use generic sys_clocksource_is_tsc() in vmx_nested_tsc_scaling_test

[Vitaly Kuznetsov]

Despite its name, system_has_stable_tsc() just checks that system
clocksource is 'tsc'; this can now be done with generic
sys_clocksource_is_tsc().

No functional change intended.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 .../kvm/x86_64/vmx_nested_tsc_scaling_test.c  | 19 +------------------
 1 file changed, 1 insertion(+), 18 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c b/tools/testing/selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c
index e710b6e7fb38..93b0a850a240 100644
--- a/tools/testing/selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c
+++ b/tools/testing/selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c
@@ -116,23 +116,6 @@ static void l1_guest_code(struct vmx_pages *vmx_pages)
 	GUEST_DONE();
 }
 
-static bool system_has_stable_tsc(void)
-{
-	bool tsc_is_stable;
-	FILE *fp;
-	char buf[4];
-
-	fp = fopen("/sys/devices/system/clocksource/clocksource0/current_clocksource", "r");
-	if (fp == NULL)
-		return false;
-
-	tsc_is_stable = fgets(buf, sizeof(buf), fp) &&
-			!strncmp(buf, "tsc", sizeof(buf));
-
-	fclose(fp);
-	return tsc_is_stable;
-}
-
 int main(int argc, char *argv[])
 {
 	struct kvm_vcpu *vcpu;
@@ -148,7 +131,7 @@ int main(int argc, char *argv[])
 
 	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_VMX));
 	TEST_REQUIRE(kvm_has_cap(KVM_CAP_TSC_CONTROL));
-	TEST_REQUIRE(system_has_stable_tsc());
+	TEST_REQUIRE(sys_clocksource_is_tsc());
 
 	/*
 	 * We set L1's scale factor to be a random number from 2 to 10.
-- 
2.43.0

[PATCH 3/5] KVM: selftests: Run clocksource dependent tests with hyperv_clocksource_tsc_page too

[Vitaly Kuznetsov]

KVM's 'gtod_is_based_on_tsc()' recognizes two clocksources: 'tsc' and
'hyperv_clocksource_tsc_page' and enables kvmclock in 'masterclock'
mode when either is in use. Transform 'sys_clocksource_is_tsc()' into
'sys_clocksource_is_based_on_tsc()' to support the later. This affects
two tests: kvm_clock_test and vmx_nested_tsc_scaling_test, both seem
to work well when system clocksource is 'hyperv_clocksource_tsc_page'.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 tools/testing/selftests/kvm/include/x86_64/processor.h        | 2 +-
 tools/testing/selftests/kvm/lib/x86_64/processor.c            | 4 +++-
 tools/testing/selftests/kvm/x86_64/kvm_clock_test.c           | 2 +-
 .../selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c        | 2 +-
 4 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
index 01eec72e0d3e..5bca8c947c82 100644
--- a/tools/testing/selftests/kvm/include/x86_64/processor.h
+++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
@@ -1271,6 +1271,6 @@ void virt_map_level(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
 #define PFERR_GUEST_PAGE_MASK	BIT_ULL(PFERR_GUEST_PAGE_BIT)
 #define PFERR_IMPLICIT_ACCESS	BIT_ULL(PFERR_IMPLICIT_ACCESS_BIT)
 
-bool sys_clocksource_is_tsc(void);
+bool sys_clocksource_is_based_on_tsc(void);
 
 #endif /* SELFTEST_KVM_PROCESSOR_H */
diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index b0c64667803d..70969d374e5b 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -1300,13 +1300,15 @@ void kvm_selftest_arch_init(void)
 	host_cpu_is_amd = this_cpu_is_amd();
 }
 
-bool sys_clocksource_is_tsc(void)
+bool sys_clocksource_is_based_on_tsc(void)
 {
 	char *clk_name = sys_get_cur_clocksource();
 	bool ret = false;
 
 	if (!strcmp(clk_name, "tsc\n"))
 		ret = true;
+	else if (!strcmp(clk_name, "hyperv_clocksource_tsc_page\n"))
+		ret = true;
 
 	free(clk_name);
 
diff --git a/tools/testing/selftests/kvm/x86_64/kvm_clock_test.c b/tools/testing/selftests/kvm/x86_64/kvm_clock_test.c
index 9deee8556b5c..eb1c12fb7656 100644
--- a/tools/testing/selftests/kvm/x86_64/kvm_clock_test.c
+++ b/tools/testing/selftests/kvm/x86_64/kvm_clock_test.c
@@ -143,7 +143,7 @@ int main(void)
 	flags = kvm_check_cap(KVM_CAP_ADJUST_CLOCK);
 	TEST_REQUIRE(flags & KVM_CLOCK_REALTIME);
 
-	TEST_REQUIRE(sys_clocksource_is_tsc());
+	TEST_REQUIRE(sys_clocksource_is_based_on_tsc());
 
 	vm = vm_create_with_one_vcpu(&vcpu, guest_main);
 
diff --git a/tools/testing/selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c b/tools/testing/selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c
index 93b0a850a240..1759fa5cb3f2 100644
--- a/tools/testing/selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c
+++ b/tools/testing/selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c
@@ -131,7 +131,7 @@ int main(int argc, char *argv[])
 
 	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_VMX));
 	TEST_REQUIRE(kvm_has_cap(KVM_CAP_TSC_CONTROL));
-	TEST_REQUIRE(sys_clocksource_is_tsc());
+	TEST_REQUIRE(sys_clocksource_is_based_on_tsc());
 
 	/*
 	 * We set L1's scale factor to be a random number from 2 to 10.
-- 
2.43.0

[PATCH 4/5] KVM: selftests: Make hyperv_clock require TSC based system clocksource

[Vitaly Kuznetsov]

KVM sets up Hyper-V TSC page clocksource for its guests when system
clocksource is 'based on TSC' (see gtod_is_based_on_tsc()), running
hyperv_clock with any other clocksource leads to imminent failure.

Add the missing requirement to make the test skip gracefully.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 tools/testing/selftests/kvm/x86_64/hyperv_clock.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/testing/selftests/kvm/x86_64/hyperv_clock.c b/tools/testing/selftests/kvm/x86_64/hyperv_clock.c
index f5e1e98f04f9..02cc3c560566 100644
--- a/tools/testing/selftests/kvm/x86_64/hyperv_clock.c
+++ b/tools/testing/selftests/kvm/x86_64/hyperv_clock.c
@@ -212,6 +212,7 @@ int main(void)
 	int stage;
 
 	TEST_REQUIRE(kvm_has_cap(KVM_CAP_HYPERV_TIME));
+	TEST_REQUIRE(sys_clocksource_is_based_on_tsc());
 
 	vm = vm_create_with_one_vcpu(&vcpu, guest_main);
 
-- 
2.43.0

[PATCH 5/5] KVM: x86: Make gtod_is_based_on_tsc() return 'bool'

[Vitaly Kuznetsov]

gtod_is_based_on_tsc() is boolean in nature, i.e. it returns '1' for good
clocksources and '0' otherwise. Moreover, its result is used raw by
kvm_get_time_and_clockread()/kvm_get_walltime_and_clockread() which are
'bool'.

No functional change intended.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 arch/x86/kvm/x86.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 27e23714e960..2aba11eb58ac 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2507,7 +2507,7 @@ static u64 compute_guest_tsc(struct kvm_vcpu *vcpu, s64 kernel_ns)
 }
 
 #ifdef CONFIG_X86_64
-static inline int gtod_is_based_on_tsc(int mode)
+static inline bool gtod_is_based_on_tsc(int mode)
 {
 	return mode == VDSO_CLOCKMODE_TSC || mode == VDSO_CLOCKMODE_HVCLOCK;
 }
-- 
2.43.0

Re: [PATCH 0/5] KVM: selftests: Fix clocksource requirements in tests

[Vitaly Kuznetsov]

Vitaly Kuznetsov <vkuznets@redhat.com> writes:

> It was discovered that 'hyperv_clock' fails miserably when the system is
> using an unsupported (by KVM) clocksource, e.g. 'kvm-clock'. The root cause
> of the failure is that 'hyperv_clock' doesn't actually check which clocksource
> is currently in use. Other tests (kvm_clock_test, vmx_nested_tsc_scaling_test)
> have the required check but each test does it on its own.
>
> Generalize clocksource checking infrastructure, make all three clocksource
> dependent tests run with 'tsc' and 'hyperv_clocksource_tsc_page', and skip
> gracefully when run in an unsupported configuration.
>
> The last patch of the series is a loosely related minor nitpick for KVM
> code itself.
>
> Vitaly Kuznetsov (5):
>   KVM: selftests: Generalize check_clocksource() from kvm_clock_test
>   KVM: selftests: Use generic sys_clocksource_is_tsc() in
>     vmx_nested_tsc_scaling_test
>   KVM: selftests: Run clocksource dependent tests with
>     hyperv_clocksource_tsc_page too
>   KVM: selftests: Make hyperv_clock require TSC based system clocksource
>   KVM: x86: Make gtod_is_based_on_tsc() return 'bool'

Ping)

-- 
Vitaly

Re: [PATCH 0/5] KVM: selftests: Fix clocksource requirements in tests

[Sean Christopherson]

On Tue, 09 Jan 2024 15:11:16 +0100, Vitaly Kuznetsov wrote:
> It was discovered that 'hyperv_clock' fails miserably when the system is
> using an unsupported (by KVM) clocksource, e.g. 'kvm-clock'. The root cause
> of the failure is that 'hyperv_clock' doesn't actually check which clocksource
> is currently in use. Other tests (kvm_clock_test, vmx_nested_tsc_scaling_test)
> have the required check but each test does it on its own.
> 
> Generalize clocksource checking infrastructure, make all three clocksource
> dependent tests run with 'tsc' and 'hyperv_clocksource_tsc_page', and skip
> gracefully when run in an unsupported configuration.
> 
> [...]

Applied to kvm-x86 selftests, thanks!

[1/5] KVM: selftests: Generalize check_clocksource() from kvm_clock_test
      https://github.com/kvm-x86/linux/commit/449d0d6ccf55
[2/5] KVM: selftests: Use generic sys_clocksource_is_tsc() in vmx_nested_tsc_scaling_test
      https://github.com/kvm-x86/linux/commit/a79036441a68
[3/5] KVM: selftests: Run clocksource dependent tests with hyperv_clocksource_tsc_page too
      https://github.com/kvm-x86/linux/commit/436e6e541cb2
[4/5] KVM: selftests: Make hyperv_clock require TSC based system clocksource
      https://github.com/kvm-x86/linux/commit/14fce852a14b
[5/5] KVM: x86: Make gtod_is_based_on_tsc() return 'bool'
      https://github.com/kvm-x86/linux/commit/57cc53712934

--
https://github.com/kvm-x86/linux/tree/next

Re: [PATCH 0/5] KVM: selftests: Fix clocksource requirements in tests

[Sean Christopherson]

On Tue, Jan 30, 2024, Sean Christopherson wrote:
> On Tue, 09 Jan 2024 15:11:16 +0100, Vitaly Kuznetsov wrote:
> > It was discovered that 'hyperv_clock' fails miserably when the system is
> > using an unsupported (by KVM) clocksource, e.g. 'kvm-clock'. The root cause
> > of the failure is that 'hyperv_clock' doesn't actually check which clocksource
> > is currently in use. Other tests (kvm_clock_test, vmx_nested_tsc_scaling_test)
> > have the required check but each test does it on its own.
> > 
> > Generalize clocksource checking infrastructure, make all three clocksource
> > dependent tests run with 'tsc' and 'hyperv_clocksource_tsc_page', and skip
> > gracefully when run in an unsupported configuration.
> > 
> > [...]
> 
> Applied to kvm-x86 selftests, thanks!
> 
> [1/5] KVM: selftests: Generalize check_clocksource() from kvm_clock_test
>       https://github.com/kvm-x86/linux/commit/449d0d6ccf55
> [2/5] KVM: selftests: Use generic sys_clocksource_is_tsc() in vmx_nested_tsc_scaling_test
>       https://github.com/kvm-x86/linux/commit/a79036441a68
> [3/5] KVM: selftests: Run clocksource dependent tests with hyperv_clocksource_tsc_page too
>       https://github.com/kvm-x86/linux/commit/436e6e541cb2
> [4/5] KVM: selftests: Make hyperv_clock require TSC based system clocksource
>       https://github.com/kvm-x86/linux/commit/14fce852a14b
> [5/5] KVM: x86: Make gtod_is_based_on_tsc() return 'bool'
>       https://github.com/kvm-x86/linux/commit/57cc53712934

FYI, I dropped the xen_shinfo patch, and past me wasn't clever enough to make sure
that patch was applied last.  New hashes are:

[1/5] KVM: selftests: Generalize check_clocksource() from kvm_clock_test
      https://github.com/kvm-x86/linux/commit/e440c5f2e3e6
[2/5] KVM: selftests: Use generic sys_clocksource_is_tsc() in vmx_nested_tsc_scaling_test
      https://github.com/kvm-x86/linux/commit/410cb01ead5b
[3/5] KVM: selftests: Run clocksource dependent tests with hyperv_clocksource_tsc_page too
      https://github.com/kvm-x86/linux/commit/09951bf2cbb3
[4/5] KVM: selftests: Make hyperv_clock require TSC based system clocksource
      https://github.com/kvm-x86/linux/commit/b6831a108be1
[5/5] KVM: x86: Make gtod_is_based_on_tsc() return 'bool'
      https://github.com/kvm-x86/linux/commit/9e62797fd7e8