[PATCH v13 25/35] x86/fred: Add a machine check entry stub for FRED
From: Xin Li <hidden>
Date: 2023-12-05 11:22:51
Also in:
kvm, linux-doc, linux-edac, lkml, xen-devel
Subsystem:
the rest, x86 architecture (32-bit and 64-bit), x86 mce infrastructure · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Tony Luck
Like #DB, when occurred on different ring level, i.e., from user or kernel context, #MCE needs to be handled on different stack: User #MCE on current task stack, while kernel #MCE on a dedicated stack. This is exactly how FRED event delivery invokes an exception handler: ring 3 event on level 0 stack, i.e., current task stack; ring 0 event on the #MCE dedicated stack specified in the IA32_FRED_STKLVLS MSR. So unlike IDT, the FRED machine check entry stub doesn't do stack switch. Tested-by: Shan Kang <redacted> Signed-off-by: Xin Li <redacted> --- Changes since v5: * Disallow #DB inside #MCE for robustness sake (Peter Zijlstra). --- arch/x86/kernel/cpu/mce/core.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+)
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 1642018dd6c9..d524eb87f76c 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c@@ -53,6 +53,7 @@ #include <asm/mce.h> #include <asm/msr.h> #include <asm/reboot.h> +#include <asm/fred.h> #include "internal.h"
@@ -2150,6 +2151,31 @@ DEFINE_IDTENTRY_MCE_USER(exc_machine_check) exc_machine_check_user(regs); local_db_restore(dr7); } + +#ifdef CONFIG_X86_FRED +/* + * When occurred on different ring level, i.e., from user or kernel + * context, #MCE needs to be handled on different stack: User #MCE + * on current task stack, while kernel #MCE on a dedicated stack. + * + * This is exactly how FRED event delivery invokes an exception + * handler: ring 3 event on level 0 stack, i.e., current task stack; + * ring 0 event on the #MCE dedicated stack specified in the + * IA32_FRED_STKLVLS MSR. So unlike IDT, the FRED machine check entry + * stub doesn't do stack switch. + */ +DEFINE_FREDENTRY_MCE(exc_machine_check) +{ + unsigned long dr7; + + dr7 = local_db_save(); + if (user_mode(regs)) + exc_machine_check_user(regs); + else + exc_machine_check_kernel(regs); + local_db_restore(dr7); +} +#endif #else /* 32bit unified entry point */ DEFINE_IDTENTRY_RAW(exc_machine_check)
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2.43.0