This is a note to let you know that I've just added the patch titled
x86/mce: Mark fatal MCE's page as poison to avoid panic in the kdump kernel
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-mce-mark-fatal-mce-s-page-as-poison-to-avoid-pan.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 0da0082f6ac3d647fb27848fcdbd4b83dc6b5243
Author: Zhiquan Li <zhiquan1.li@xxxxxxxxx>
Date: Thu Oct 26 08:39:03 2023 +0800
x86/mce: Mark fatal MCE's page as poison to avoid panic in the kdump kernel
[ Upstream commit 9f3b130048bfa2e44a8cfb1b616f826d9d5d8188 ]
Memory errors don't happen very often, especially fatal ones. However,
in large-scale scenarios such as data centers, that probability
increases with the amount of machines present.
When a fatal machine check happens, mce_panic() is called based on the
severity grading of that error. The page containing the error is not
marked as poison.
However, when kexec is enabled, tools like makedumpfile understand when
pages are marked as poison and do not touch them so as not to cause
a fatal machine check exception again while dumping the previous
kernel's memory.
Therefore, mark the page containing the error as poisoned so that the
kexec'ed kernel can avoid accessing the page.
[ bp: Rewrite commit message and comment. ]
Co-developed-by: Youquan Song <youquan.song@xxxxxxxxx>
Signed-off-by: Youquan Song <youquan.song@xxxxxxxxx>
Signed-off-by: Zhiquan Li <zhiquan1.li@xxxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Reviewed-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Link: https://lore.kernel.org/r/20231014051754.3759099-1-zhiquan1.li@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 9b98a7d8ac60..84c0e5c2518c 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -42,6 +42,7 @@
#include <linux/export.h>
#include <linux/jump_label.h>
#include <linux/set_memory.h>
+#include <linux/kexec.h>
#include <asm/intel-family.h>
#include <asm/processor.h>
@@ -315,6 +316,7 @@ static noinstr void mce_panic(const char *msg, struct mce *final, char *exp)
struct llist_node *pending;
struct mce_evt_llist *l;
int apei_err = 0;
+ struct page *p;
/*
* Allow instrumentation around external facilities usage. Not that it
@@ -370,6 +372,20 @@ static noinstr void mce_panic(const char *msg, struct mce *final, char *exp)
if (!fake_panic) {
if (panic_timeout == 0)
panic_timeout = mca_cfg.panic_timeout;
+
+ /*
+ * Kdump skips the poisoned page in order to avoid
+ * touching the error bits again. Poison the page even
+ * if the error is fatal and the machine is about to
+ * panic.
+ */
+ if (kexec_crash_loaded()) {
+ if (final && (final->status & MCI_STATUS_ADDRV)) {
+ p = pfn_to_online_page(final->addr >> PAGE_SHIFT);
+ if (p)
+ SetPageHWPoison(p);
+ }
+ }
panic(msg);
} else
pr_emerg(HW_ERR "Fake kernel panic: %s\n", msg);
