[PATCH 2/2] x86/MCE: Don't call kill_me_now() directly

From: Yazen Ghannam <yazen.ghannam@amd.com>

Always call kill_me_maybe() in order to attempt memory recovery. This
ensures that any memory associated with the error is properly marked as
poison.

This is needed for errors that occur on memory, but that do not have
MCG_STATUS[RIPV] set. One example is data poison consumption through the
instruction fetch units on AMD Zen-based systems.

The MF_MUST_KILL flag is passed to memory_failure() when
MCG_STATUS[RIPV] is not set. So the associated process will still be
killed.

Cc: <redacted>
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
---
 arch/x86/kernel/cpu/mce/core.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 308fb644b94a..9040d45ed997 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c

@@ -1285,10 +1285,7 @@ static void queue_task_work(struct mce *m, int kill_current_task)
 	current->mce_ripv = !!(m->mcgstatus & MCG_STATUS_RIPV);
 	current->mce_whole_page = whole_page(m);
 
-	if (kill_current_task)
-		current->mce_kill_me.func = kill_me_now;
-	else
-		current->mce_kill_me.func = kill_me_maybe;
+	current->mce_kill_me.func = kill_me_maybe;
 
 	task_work_add(current, &current->mce_kill_me, TWA_RESUME);
 }

-- 
2.25.1

On Tue, May 04, 2021 at 05:47:12PM +0000, Yazen Ghannam wrote:

Could we just get rid of kill_me_now() at the same time? It's only
one line, and with this change only called in one place (from
kill_me_maybe()) ... just put the force_sig(SIGBUS); inline?

-Tony

On Tue, May 04, 2021 at 11:07:34AM -0700, Luck, Tony wrote:

On Tue, May 04, 2021 at 05:47:12PM +0000, Yazen Ghannam wrote:

...

quoted

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 308fb644b94a..9040d45ed997 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c

@@ -1285,10 +1285,7 @@ static void queue_task_work(struct mce *m, int kill_current_task)
 	current->mce_ripv = !!(m->mcgstatus & MCG_STATUS_RIPV);
 	current->mce_whole_page = whole_page(m);
 
-	if (kill_current_task)
-		current->mce_kill_me.func = kill_me_now;
-	else
-		current->mce_kill_me.func = kill_me_maybe;
+	current->mce_kill_me.func = kill_me_maybe;
 
 	task_work_add(current, &current->mce_kill_me, TWA_RESUME);
 }

Could we just get rid of kill_me_now() at the same time? It's only
one line, and with this change only called in one place (from
kill_me_maybe()) ... just put the force_sig(SIGBUS); inline?

Okay, will do.

Thanks,
Yazen