[PATCH] x86/mce: Set PG_hwpoison page flag to avoid the capture kernel panic

[Tony Luck]

From: Zhiquan Li <zhiquan1.li@xxxxxxxxx>

Kdump can exclude the HWPosion page to avoid touch the error page
again, the prerequisite is the PG_hwpoison page flag is set.
However, for some MCE fatal error cases, there are no opportunity
to queue a task for calling memory_failure(), as a result,
the capture kernel touches the error page again and panics.

Add function mce_set_page_hwpoison_now() which mark a page as
HWPoison before kernel panic() for MCE error, so that the dump
program can check and skip the error page and prevent the capture
kernel panic.

[Tony: Changed TestSetPageHWPoison() to SetPageHWPoison()]

Co-developedd-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: Tony Luck <tony.luck@xxxxxxxxx>
---
 arch/x86/kernel/cpu/mce/core.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 2c8ec5c71712..0630999c6311 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -162,6 +162,24 @@ void mce_unregister_decode_chain(struct notifier_block *nb)
 }
 EXPORT_SYMBOL_GPL(mce_unregister_decode_chain);
 
+/*
+ * Kdump can exclude the HWPosion page to avoid touch the error page again,
+ * the prerequisite is the PG_hwpoison page flag is set. However, for some
+ * MCE fatal error cases, there are no opportunity to queue a task
+ * for calling memory_failure(), as a result, the capture kernel panic.
+ * This function mark the page as HWPoison before kernel panic() for MCE.
+ */
+static void mce_set_page_hwpoison_now(unsigned long pfn)
+{
+	struct page *p;
+
+	/* TODO: need to handle other sort of page, like SGX, PMEM and
+	 * HugeTLB pages*/
+	p = pfn_to_online_page(pfn);
+	if (p)
+		SetPageHWPoison(p);
+}
+
 static void __print_mce(struct mce *m)
 {
 	pr_emerg(HW_ERR "CPU %d: Machine Check%s: %Lx Bank %d: %016Lx\n",
@@ -292,6 +310,8 @@ 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;
+		if (final && (final->status & MCI_STATUS_ADDRV))
+			 mce_set_page_hwpoison_now(final->addr >> PAGE_SHIFT);
 		panic(msg);
 	} else
 		pr_emerg(HW_ERR "Fake kernel panic: %s\n", msg);
-- 
2.39.1