[PATCH 5/5] x86/platform/UV: Add check of TSC state set by UV BIOS

[mike.travis]

Insert a check early in UV system startup that checks whether BIOS was
able to obtain satisfactory TSC Sync stability.  If not, it usually
is caused by an error in the external TSC clock generation source.
In this case the best fallback is to use the builtin hardware RTC
as the kernel will not be able to set an accurate TSC sync either.

Signed-off-by: Mike Travis <mike.travis@xxxxxxx>
Reviewed-by: Dimitri Sivanich <dimitri.sivanich@xxxxxxx>
Reviewed-by: Russ Anderson <russ.anderson@xxxxxxx>
Reviewed-by: Andrew Banman <andrew.abanman@xxxxxxx>
---
v2: Patches merged against 4.14.0-rc4
---
 arch/x86/include/asm/uv/uv_hub.h   |   23 +++++++++++++++----
 arch/x86/kernel/apic/x2apic_uv_x.c |   43 +++++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+), 5 deletions(-)

--- linux.orig/arch/x86/include/asm/uv/uv_hub.h
+++ linux/arch/x86/include/asm/uv/uv_hub.h
@@ -776,23 +776,36 @@ static inline int uv_num_possible_blades
 extern void uv_nmi_setup(void);
 extern void uv_nmi_setup_hubless(void);
 
+/* BIOS/Kernel flags exchange MMR */
+#define UVH_BIOS_KERNEL_MMR		UVH_SCRATCH5
+#define UVH_BIOS_KERNEL_MMR_ALIAS	UVH_SCRATCH5_ALIAS
+#define UVH_BIOS_KERNEL_MMR_ALIAS_2	UVH_SCRATCH5_ALIAS_2
+
+/* TSC sync valid, set by BIOS */
+#define UVH_TSC_SYNC_MMR	UVH_BIOS_KERNEL_MMR
+#define UVH_TSC_SYNC_SHIFT	10
+#define UVH_TSC_SYNC_SHIFT_UV2K	16	/* UV2/3k have different bits */
+#define UVH_TSC_SYNC_MASK	3	/* 0011 */
+#define UVH_TSC_SYNC_VALID	3	/* 0011 */
+#define UVH_TSC_SYNC_INVALID	2	/* 0010 */
+
 /* BMC sets a bit this MMR non-zero before sending an NMI */
-#define UVH_NMI_MMR		UVH_SCRATCH5
-#define UVH_NMI_MMR_CLEAR	UVH_SCRATCH5_ALIAS
+#define UVH_NMI_MMR		UVH_BIOS_KERNEL_MMR
+#define UVH_NMI_MMR_CLEAR	UVH_BIOS_KERNEL_MMR_ALIAS
 #define UVH_NMI_MMR_SHIFT	63
-#define	UVH_NMI_MMR_TYPE	"SCRATCH5"
+#define UVH_NMI_MMR_TYPE	"SCRATCH5"
 
 /* Newer SMM NMI handler, not present in all systems */
 #define UVH_NMI_MMRX		UVH_EVENT_OCCURRED0
 #define UVH_NMI_MMRX_CLEAR	UVH_EVENT_OCCURRED0_ALIAS
 #define UVH_NMI_MMRX_SHIFT	UVH_EVENT_OCCURRED0_EXTIO_INT0_SHFT
-#define	UVH_NMI_MMRX_TYPE	"EXTIO_INT0"
+#define UVH_NMI_MMRX_TYPE	"EXTIO_INT0"
 
 /* Non-zero indicates newer SMM NMI handler present */
 #define UVH_NMI_MMRX_SUPPORTED	UVH_EXTIO_INT0_BROADCAST
 
 /* Indicates to BIOS that we want to use the newer SMM NMI handler */
-#define UVH_NMI_MMRX_REQ	UVH_SCRATCH5_ALIAS_2
+#define UVH_NMI_MMRX_REQ	UVH_BIOS_KERNEL_MMR_ALIAS_2
 #define UVH_NMI_MMRX_REQ_SHIFT	62
 
 struct uv_hub_nmi_s {
--- linux.orig/arch/x86/kernel/apic/x2apic_uv_x.c
+++ linux/arch/x86/kernel/apic/x2apic_uv_x.c
@@ -154,6 +154,48 @@ static int __init early_get_pnodeid(void
 	return pnode;
 }
 
+static void uv_tsc_check_sync(void)
+{
+	u64 mmr;
+	int sync_state;
+	int mmr_shift;
+	char *state;
+	bool valid;
+
+	/* Accommodate different UV arch BIOSes */
+	mmr = uv_early_read_mmr(UVH_TSC_SYNC_MMR);
+	mmr_shift =
+		is_uv1_hub() ? 0 :
+		is_uv2_hub() ? UVH_TSC_SYNC_SHIFT_UV2K : UVH_TSC_SYNC_SHIFT;
+	if (mmr_shift)
+		sync_state = (mmr >> mmr_shift) & UVH_TSC_SYNC_MASK;
+	else
+		sync_state = 0;
+
+	switch (sync_state) {
+	case UVH_TSC_SYNC_VALID:
+		state = "in sync";
+		valid = true;
+		break;
+
+	case UVH_TSC_SYNC_INVALID:
+		state = "unstable";
+		valid = false;
+		break;
+	default:
+		state = "unknown: assuming valid";
+		valid = true;
+		break;
+	}
+	pr_info("UV: TSC sync state from BIOS:0%d(%s)\n", sync_state, state);
+
+	/* Mark flag that says TSC != 0 is valid for socket 0 */
+	if (valid)
+		mark_tsc_async_resets("UV BIOS");
+	else
+		mark_tsc_unstable("UV BIOS");
+}
+
 /* [Copied from arch/x86/kernel/cpu/topology.c:detect_extended_topology()] */
 
 #define SMT_LEVEL			0	/* Leaf 0xb SMT level */
@@ -288,6 +330,7 @@ static int __init uv_acpi_madt_oem_check
 	}
 
 	pr_info("UV: OEM IDs %s/%s, System/HUB Types %d/%d, uv_apic %d\n", oem_id, oem_table_id, uv_system_type, uv_min_hub_revision_id, uv_apic);
+	uv_tsc_check_sync();
 
 	return uv_apic;
 

--