x86/ras: Flip the TSC-adding logic

Add the TSC value to the MCE record only when the MCE being logged is
precise, i.e., it is logged as an exception or an MCE-related interrupt.

So it doesn't look particularly easy to do without touching/changing a
bunch of places. That's why I'm trying tricks first.

For example, the mce-apei.c case I'm addressing by setting ->tsc only
for errors of panic severity. The idea there is, that, panic errors will
have raised an #MC and not polled.

And then instead of propagating a flag to mce_setup(), it seems
easier/less code to set ->tsc depending on the call sites, i.e.,
are we polling or are we preparing an MCE record in an exception
handler/thresholding interrupt.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Yazen Ghannam <Yazen.Ghannam@amd.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Link: http://lkml.kernel.org/r/20170123183514.13356-5-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

3 files changed, 9 insertions, 11 deletions

diff --git a/arch/x86/kernel/cpu/mcheck/mce-apei.c b/arch/x86/kernel/cpu/mcheck/mce-apei.c
index 83f1a98d37db..2eee85379689 100644
--- a/arch/x86/kernel/cpu/mcheck/mce-apei.c
+++ b/arch/x86/kernel/cpu/mcheck/mce-apei.c
@@ -52,8 +52,11 @@ void apei_mce_report_mem_error(int severity, struct cper_sec_mem_err *mem_err)
 
         if (severity >= GHES_SEV_RECOVERABLE)
                 m.status |= MCI_STATUS_UC;
-        if (severity >= GHES_SEV_PANIC)
+
+        if (severity >= GHES_SEV_PANIC) {
                 m.status |= MCI_STATUS_PCC;
+                m.tsc = rdtsc();
+        }
 
         m.addr = mem_err->physical_addr;
         mce_log(&m);
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 6eef6fde0f02..ca15a7e1f97d 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -128,7 +128,6 @@ void mce_setup(struct mce *m)
 {
         memset(m, 0, sizeof(struct mce));
         m->cpu = m->extcpu = smp_processor_id();
-        m->tsc = rdtsc();
         /* We hope get_seconds stays lockless */
         m->time = get_seconds();
         m->cpuvendor = boot_cpu_data.x86_vendor;
@@ -710,14 +709,8 @@ bool machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
 
         mce_gather_info(&m, NULL);
 
-        /*
-         * m.tsc was set in mce_setup(). Clear it if not requested.
-         *
-         * FIXME: Propagate @flags to mce_gather_info/mce_setup() to avoid
-         *        that dance.
-         */
-        if (!(flags & MCP_TIMESTAMP))
-                m.tsc = 0;
+        if (flags & MCP_TIMESTAMP)
+                m.tsc = rdtsc();
 
         for (i = 0; i < mca_cfg.banks; i++) {
                 if (!mce_banks[i].ctl || !test_bit(i, *b))
@@ -1156,6 +1149,7 @@ void do_machine_check(struct pt_regs *regs, long error_code)
                 goto out;
 
         mce_gather_info(&m, regs);
+        m.tsc = rdtsc();
 
         final = this_cpu_ptr(&mces_seen);
         *final = m;
diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c b/arch/x86/kernel/cpu/mcheck/mce_amd.c
index 776379e4a39c..9e5427df3243 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
@@ -778,7 +778,8 @@ __log_error(unsigned int bank, bool deferred_err, bool threshold_err, u64 misc)
         mce_setup(&m);
 
         m.status = status;
-        m.bank = bank;
+        m.bank   = bank;
+        m.tsc    = rdtsc();
 
         if (threshold_err)
                 m.misc = misc;