Cpuid leaf 4 contains information about how the state of the tsc, its
mode, and some additional information. A commit that is queued for
linux would like to use this to determine whether the tsc mode has been
set to 'no emulation' in order to make some decisions about which
clocksource is more reliable.
Expose this information in the public API headers so that they can
subsequently be imported into linux and used there.
Link: https://lore.kernel.org/xen-devel/eda8d9f2-3013-1b68-0df8-64d7f13ee35e@suse.com/
Link: https://lore.kernel.org/xen-devel/0835453d-9617-48d5-b2dc-77a2ac298bad@oracle.com/
Signed-off-by: Krister Johansen <kjlx@templeofstupid.com>
---
v4
- Rename TSC_MODE_NEVER_EMULATE_TSC_AUX to TSC_MODE_PVRDTSCP (feedback from
Jan Buelich)
v3
- Additional formating cleanups (feedback from Jan Buelich)
- Ensure that TSC_MODE #defines match the names of those in time.h (feedback
from Jan Buelich)
v2:
- Fix whitespace between comment and #defines (feedback from Jan Beulich)
- Add tsc mode 3: no emulate TSC_AUX (feedback from Jan Beulich)
---
xen/include/public/arch-x86/cpuid.h | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/xen/include/public/arch-x86/cpuid.h b/xen/include/public/arch-x86/cpuid.h
index 7ecd16ae05..9d02f86564 100644
--- a/xen/include/public/arch-x86/cpuid.h
+++ b/xen/include/public/arch-x86/cpuid.h
@@ -72,6 +72,15 @@
* Sub-leaf 2: EAX: host tsc frequency in kHz
*/
+#define XEN_CPUID_TSC_EMULATED (1u << 0)
+#define XEN_CPUID_HOST_TSC_RELIABLE (1u << 1)
+#define XEN_CPUID_RDTSCP_INSTR_AVAIL (1u << 2)
+
+#define XEN_CPUID_TSC_MODE_DEFAULT (0)
+#define XEN_CPUID_TSC_MODE_ALWAYS_EMULATE (1u)
+#define XEN_CPUID_TSC_MODE_NEVER_EMULATE (2u)
+#define XEN_CPUID_TSC_MODE_PVRDTSCP (3u)
+
/*
* Leaf 5 (0x40000x04)
* HVM-specific features
--
2.25.1