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Commit dad1743e authored by Tony Luck's avatar Tony Luck
Browse files

x86/mce: Only restart instruction after machine check recovery if it is safe 



Section 15.3.1.2 of the software developer manual has this to say about the
RIPV bit in the IA32_MCG_STATUS register:

  RIPV (restart IP valid) flag, bit 0 — Indicates (when set) that program
  execution can be restarted reliably at the instruction pointed to by the
  instruction pointer pushed on the stack when the machine-check exception
  is generated.  When clear, the program cannot be reliably restarted at
  the pushed instruction pointer.

We need to save the state of this bit in do_machine_check() and use it
in mce_notify_process() to force a signal; even if memory_failure() says
it made a complete recovery ... e.g. replaced a clean LRU page.

Acked-by: default avatarBorislav Petkov <bp@amd64.org>
Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
parent d48b97b4

arch/x86/kernel/cpu/mcheck/mce.c

+11 −3
Original line number Diff line number Diff line
@@ -945,9 +945,10 @@ struct mce_info { 
	atomic_t		inuse;

	struct task_struct	*t;

	__u64			paddr;

	int			restartable;

} mce_info[MCE_INFO_MAX];



static void mce_save_info(__u64 addr)

static void mce_save_info(__u64 addr, int c)

{

	struct mce_info *mi;
@@ -955,6 +956,7 @@ static void mce_save_info(__u64 addr) 
		if (atomic_cmpxchg(&mi->inuse, 0, 1) == 0) {

			mi->t = current;

			mi->paddr = addr;

			mi->restartable = c;

			return;

		}

	}
@@ -1130,7 +1132,7 @@ void do_machine_check(struct pt_regs *regs, long error_code) 
			mce_panic("Fatal machine check on current CPU", &m, msg);

		if (worst == MCE_AR_SEVERITY) {

			/* schedule action before return to userland */

			mce_save_info(m.addr);

			mce_save_info(m.addr, m.mcgstatus & MCG_STATUS_RIPV);

			set_thread_flag(TIF_MCE_NOTIFY);

		} else if (kill_it) {

			force_sig(SIGBUS, current);
@@ -1179,7 +1181,13 @@ void mce_notify_process(void) 


	pr_err("Uncorrected hardware memory error in user-access at %llx",

		 mi->paddr);

	if (memory_failure(pfn, MCE_VECTOR, MF_ACTION_REQUIRED) < 0) {

	/*

	 * We must call memory_failure() here even if the current process is

	 * doomed. We still need to mark the page as poisoned and alert any

	 * other users of the page.

	 */

	if (memory_failure(pfn, MCE_VECTOR, MF_ACTION_REQUIRED) < 0 ||

			   mi->restartable == 0) {

		pr_err("Memory error not recovered");

		force_sig(SIGBUS, current);

	}