x86/platform/UV: Add check of TSC state set by UV BIOS

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@hpe.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Dimitri Sivanich <dimitri.sivanich@hpe.com>
Reviewed-by: Russ Anderson <russ.anderson@hpe.com>
Reviewed-by: Andrew Banman <andrew.abanman@hpe.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Andrew Banman <andrew.banman@hpe.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Bin Gao <bin.gao@linux.intel.com>
Link: https://lkml.kernel.org/r/20171012163202.406294490@stormcage.americas.sgi.com

2 files changed, 61 insertions, 5 deletions

diff --git a/arch/x86/include/asm/uv/uv_hub.h b/arch/x86/include/asm/uv/uv_hub.h
index 9cffb44a3cf5..036e26d63d9a 100644
--- a/arch/x86/include/asm/uv/uv_hub.h
+++ b/arch/x86/include/asm/uv/uv_hub.h
@@ -776,23 +776,36 @@ static inline int uv_num_possible_blades(void)
 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 {
diff --git a/arch/x86/kernel/apic/x2apic_uv_x.c b/arch/x86/kernel/apic/x2apic_uv_x.c
index 0d57bb9079c9..440825478bbd 100644
--- a/arch/x86/kernel/apic/x2apic_uv_x.c
+++ b/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(char *oem_id, char *oem_table_id)
         }
 
         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;