x86/fred: Add a machine check entry stub for FRED
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 the FRED machine check entry stub doesn't do stack switch. Signed-off-by: Xin Li <xin3.li@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Tested-by: Shan Kang <shan.kang@intel.com> Link: https://lore.kernel.org/r/20231205105030.8698-26-xin3.li@intel.com
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@ -46,6 +46,7 @@
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#include <linux/hardirq.h>
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#include <linux/kexec.h>
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#include <asm/fred.h>
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#include <asm/intel-family.h>
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#include <asm/processor.h>
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#include <asm/traps.h>
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@ -2166,6 +2167,31 @@ DEFINE_IDTENTRY_MCE_USER(exc_machine_check)
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exc_machine_check_user(regs);
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local_db_restore(dr7);
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}
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#ifdef CONFIG_X86_FRED
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/*
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* When occurred on different ring level, i.e., from user or kernel
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* context, #MCE needs to be handled on different stack: User #MCE
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* on current task stack, while kernel #MCE on a dedicated stack.
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*
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* This is exactly how FRED event delivery invokes an exception
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* handler: ring 3 event on level 0 stack, i.e., current task stack;
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* ring 0 event on the #MCE dedicated stack specified in the
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* IA32_FRED_STKLVLS MSR. So unlike IDT, the FRED machine check entry
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* stub doesn't do stack switch.
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*/
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DEFINE_FREDENTRY_MCE(exc_machine_check)
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{
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unsigned long dr7;
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dr7 = local_db_save();
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if (user_mode(regs))
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exc_machine_check_user(regs);
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else
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exc_machine_check_kernel(regs);
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local_db_restore(dr7);
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}
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#endif
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#else
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/* 32bit unified entry point */
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DEFINE_IDTENTRY_RAW(exc_machine_check)
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