[PATCH v2] x86/tsc: Disable clocksource watchdog for TSC on recent UV

[Dimitri Sivanich <sivanich@hpe.com>]

Disable clocksource watchdog checking on recent and future UV platforms
to avoid false positives.

Commits 'b50db7095fe0 ("x86/tsc: Disable clocksource watchdog for TSC on
qualified platforms")' and '233756a640be ("Extend watchdog check exemption
to 4-Sockets platform")' were introduced to avoid an issue where the TSC
is falsely declared unstable by exempting qualified platforms of up to
4-sockets from TSC clocksource watchdog checking.  Extend that exemption
to include recent and future UV platforms.

Signed-off-by: Dimitri Sivanich <sivanich@hpe.com>
---

Version 2:  Fixes a build error that occurs when UV is not configured.

 arch/x86/include/asm/uv/uv_hub.h | 8 ++++++++
 arch/x86/kernel/tsc.c            | 4 ++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/uv/uv_hub.h b/arch/x86/include/asm/uv/uv_hub.h
index ea877fd83114..0ac079e820b0 100644
--- a/arch/x86/include/asm/uv/uv_hub.h
+++ b/arch/x86/include/asm/uv/uv_hub.h
@@ -26,6 +26,7 @@
 #include <asm/irq_vectors.h>
 #include <asm/io_apic.h>
 
+#ifdef CONFIG_X86_UV
 
 /*
  * Addressing Terminology
@@ -785,5 +786,12 @@ static inline int uv_get_min_hub_revision_id(void)
 	return uv_hub_info->hub_revision;
 }
 
+#else /* !X86_UV */
+
+static inline int is_uvx_hub(void) { return 0; }
+static inline int is_uvy_hub(void) { return 0; }
+static inline int is_uv_hub(void) { return 0; }
+
+#endif /* X86_UV */
 #endif /* CONFIG_X86_64 */
 #endif /* _ASM_X86_UV_UV_HUB_H */
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 87e749106dda..23727d7214e6 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -31,7 +31,7 @@
 #include <asm/i8259.h>
 #include <asm/msr.h>
 #include <asm/topology.h>
-#include <asm/uv/uv.h>
+#include <asm/uv/uv_hub.h>
 #include <asm/sev.h>
 
 unsigned int __read_mostly cpu_khz;	/* TSC clocks / usec, not used here */
@@ -1261,7 +1261,7 @@ static void __init check_system_tsc_reliable(void)
 	if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) &&
 	    boot_cpu_has(X86_FEATURE_NONSTOP_TSC) &&
 	    boot_cpu_has(X86_FEATURE_TSC_ADJUST) &&
-	    topology_max_packages() <= 4)
+	    (topology_max_packages() <= 4 || is_uvy_hub()))
 		tsc_disable_clocksource_watchdog();
 }
 
-- 
2.43.0