x86/mce: Simplify AMD severity grading logic

The MCE handler needs to understand the severity of the machine errors to
act accordingly. Simplify the AMD grading logic following a logic that
closely resembles the descriptions of the public PPR documents. This will
help include more fine-grained grading of errors in the future.

  [ bp: Touchups. ]

Signed-off-by: Carlos Bilbao <carlos.bilbao@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Yazen Ghannam <yazen.ghannam@amd.com>
Link: https://lore.kernel.org/r/20220405183212.354606-2-carlos.bilbao@amd.com

diff --git a/arch/x86/kernel/cpu/mce/severity.c b/arch/x86/kernel/cpu/mce/severity.c
index 1add869353497d690dc4cf0ca6054b41823f8b5a..d842148f9c390b0e5a5ec57961782763f9863ffe 100644 (file)
--- a/arch/x86/kernel/cpu/mce/severity.c
+++ b/arch/x86/kernel/cpu/mce/severity.c
@@ -301,85 +301,56 @@ static noinstr int error_context(struct mce *m, struct pt_regs *regs)
        }
 }
 
-static __always_inline int mce_severity_amd_smca(struct mce *m, enum context err_ctx)
+/* See AMD PPR(s) section Machine Check Error Handling. */
+static noinstr int mce_severity_amd(struct mce *m, struct pt_regs *regs, char **msg, bool is_excp)
 {
-       u64 mcx_cfg;
+       int ret;
 
        /*
-        * We need to look at the following bits:
-        * - "succor" bit (data poisoning support), and
-        * - TCC bit (Task Context Corrupt)
-        * in MCi_STATUS to determine error severity.
+        * Default return value: Action required, the error must be handled
+        * immediately.
         */
-       if (!mce_flags.succor)
-               return MCE_PANIC_SEVERITY;
-
-       mcx_cfg = mce_rdmsrl(MSR_AMD64_SMCA_MCx_CONFIG(m->bank));
-
-       /* TCC (Task context corrupt). If set and if IN_KERNEL, panic. */
-       if ((mcx_cfg & MCI_CONFIG_MCAX) &&
-           (m->status & MCI_STATUS_TCC) &&
-           (err_ctx == IN_KERNEL))
-               return MCE_PANIC_SEVERITY;
-
-        /* ...otherwise invoke hwpoison handler. */
-       return MCE_AR_SEVERITY;
-}
-
-/*
- * See AMD Error Scope Hierarchy table in a newer BKDG. For example
- * 49125_15h_Models_30h-3Fh_BKDG.pdf, section "RAS Features"
- */
-static noinstr int mce_severity_amd(struct mce *m, struct pt_regs *regs, char **msg, bool is_excp)
-{
-       enum context ctx = error_context(m, regs);
+       ret = MCE_AR_SEVERITY;
 
        /* Processor Context Corrupt, no need to fumble too much, die! */
-       if (m->status & MCI_STATUS_PCC)
-               return MCE_PANIC_SEVERITY;
-
-       if (m->status & MCI_STATUS_UC) {
-
-               if (ctx == IN_KERNEL)
-                       return MCE_PANIC_SEVERITY;
+       if (m->status & MCI_STATUS_PCC) {
+               ret = MCE_PANIC_SEVERITY;
+               goto out;
+       }
 
-               /*
-                * On older systems where overflow_recov flag is not present, we
-                * should simply panic if an error overflow occurs. If
-                * overflow_recov flag is present and set, then software can try
-                * to at least kill process to prolong system operation.
-                */
-               if (mce_flags.overflow_recov) {
-                       if (mce_flags.smca)
-                               return mce_severity_amd_smca(m, ctx);
-
-                       /* kill current process */
-                       return MCE_AR_SEVERITY;
-               } else {
-                       /* at least one error was not logged */
-                       if (m->status & MCI_STATUS_OVER)
-                               return MCE_PANIC_SEVERITY;
-               }
-
-               /*
-                * For any other case, return MCE_UC_SEVERITY so that we log the
-                * error and exit #MC handler.
-                */
-               return MCE_UC_SEVERITY;
+       if (m->status & MCI_STATUS_DEFERRED) {
+               ret = MCE_DEFERRED_SEVERITY;
+               goto out;
        }
 
        /*
-        * deferred error: poll handler catches these and adds to mce_ring so
-        * memory-failure can take recovery actions.
+        * If the UC bit is not set, the system either corrected or deferred
+        * the error. No action will be required after logging the error.
         */
-       if (m->status & MCI_STATUS_DEFERRED)
-               return MCE_DEFERRED_SEVERITY;
+       if (!(m->status & MCI_STATUS_UC)) {
+               ret = MCE_KEEP_SEVERITY;
+               goto out;
+       }
 
        /*
-        * corrected error: poll handler catches these and passes responsibility
-        * of decoding the error to EDAC
+        * On MCA overflow, without the MCA overflow recovery feature the
+        * system will not be able to recover, panic.
         */
-       return MCE_KEEP_SEVERITY;
+       if ((m->status & MCI_STATUS_OVER) && !mce_flags.overflow_recov) {
+               ret = MCE_PANIC_SEVERITY;
+               goto out;
+       }
+
+       if (!mce_flags.succor) {
+               ret = MCE_PANIC_SEVERITY;
+               goto out;
+       }
+
+       if (error_context(m, regs) == IN_KERNEL)
+               ret = MCE_PANIC_SEVERITY;
+
+out:
+       return ret;
 }
 
 static noinstr int mce_severity_intel(struct mce *m, struct pt_regs *regs, char **msg, bool is_excp)