A long time ago, Linux cleared IA32_MCG_STATUS at the very end of machine
check processing.
Then we added some fancy recovery and IST manipulation in:
commit d4812e169de4 ("x86, mce: Get rid of TIF_MCE_NOTIFY and associated mce
tricks")
and clearing IA32_MCG_STATUS was pulled earlier in the function.
Next change moved the actual recovery out of do_machine_check() and just
used task_work_add() to schedule it later (before returning to the user):
commit 5567d11c21a1 ("x86/mce: Send #MC singal from task work")
Most recently the fancy IST footwork was removed as no longer needed:
commit b052df3da821 ("x86/entry: Get rid of ist_begin/end_non_atomic()")
At this point there is no reason remaining to clear IA32_MCG_STATUS early.
It can move back to the very end of the function.
Also moved sync_core(). The comments for this function say that it should
only be called when instructions have been changed/re-mapped. Recovery for
an instruction fetch may change the physical address. But that doesn't happen
until the scheduled work runs (which could be on another CPU).
Reported-by: Gabriele Paoloni <gabriele.paol...@intel.com>
Signed-off-by: Tony Luck <tony.l...@intel.com>
---
arch/x86/kernel/cpu/mce/core.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index f43a78bde670..0ba24dfffdb2 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1190,6 +1190,7 @@ static void kill_me_maybe(struct callback_head *cb)
if (!memory_failure(p->mce_addr >> PAGE_SHIFT, flags)) {
set_mce_nospec(p->mce_addr >> PAGE_SHIFT, p->mce_whole_page);
+ sync_core();
return;
}
@@ -1330,12 +1331,8 @@ noinstr void do_machine_check(struct pt_regs *regs)
if (worst > 0)
irq_work_queue(&mce_irq_work);
- mce_wrmsrl(MSR_IA32_MCG_STATUS, 0);
-
- sync_core();
-
if (worst != MCE_AR_SEVERITY && !kill_it)
- return;
+ goto out;
/* Fault was in user mode and we need to take some action */
if ((m.cs & 3) == 3) {
@@ -1364,6 +1361,8 @@ noinstr void do_machine_check(struct pt_regs *regs)
mce_panic("Failed kernel mode recovery", &m,
msg);
}
}
+out:
+ mce_wrmsrl(MSR_IA32_MCG_STATUS, 0);
}
EXPORT_SYMBOL_GPL(do_machine_check);
--
2.21.1
