6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Zhiquan Li zhiquan1.li@intel.com
[ 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@intel.com Signed-off-by: Youquan Song youquan.song@intel.com Signed-off-by: Zhiquan Li zhiquan1.li@intel.com Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Reviewed-by: Naoya Horiguchi naoya.horiguchi@nec.com Link: https://lore.kernel.org/r/20231014051754.3759099-1-zhiquan1.li@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kernel/cpu/mce/core.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c index 6f35f724cc14..20ab11aec60b 100644 --- a/arch/x86/kernel/cpu/mce/core.c +++ b/arch/x86/kernel/cpu/mce/core.c @@ -44,6 +44,7 @@ #include <linux/sync_core.h> #include <linux/task_work.h> #include <linux/hardirq.h> +#include <linux/kexec.h>
#include <asm/intel-family.h> #include <asm/processor.h> @@ -233,6 +234,7 @@ 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 @@ -286,6 +288,20 @@ 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);