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-rw-r--r--arch/x86/kernel/cpu/mcheck/mce.c43
1 files changed, 43 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 6dde0497efc7..3b413065c613 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -51,6 +51,7 @@
#include <asm/mce.h>
#include <asm/msr.h>
#include <asm/reboot.h>
+#include <asm/set_memory.h>
#include "mce-internal.h"
@@ -1051,6 +1052,48 @@ static int do_memory_failure(struct mce *m)
return ret;
}
+#if defined(arch_unmap_kpfn) && defined(CONFIG_MEMORY_FAILURE)
+
+void arch_unmap_kpfn(unsigned long pfn)
+{
+ unsigned long decoy_addr;
+
+ /*
+ * Unmap this page from the kernel 1:1 mappings to make sure
+ * we don't log more errors because of speculative access to
+ * the page.
+ * We would like to just call:
+ * set_memory_np((unsigned long)pfn_to_kaddr(pfn), 1);
+ * but doing that would radically increase the odds of a
+ * speculative access to the posion page because we'd have
+ * the virtual address of the kernel 1:1 mapping sitting
+ * around in registers.
+ * Instead we get tricky. We create a non-canonical address
+ * that looks just like the one we want, but has bit 63 flipped.
+ * This relies on set_memory_np() not checking whether we passed
+ * a legal address.
+ */
+
+/*
+ * Build time check to see if we have a spare virtual bit. Don't want
+ * to leave this until run time because most developers don't have a
+ * system that can exercise this code path. This will only become a
+ * problem if/when we move beyond 5-level page tables.
+ *
+ * Hard code "9" here because cpp doesn't grok ilog2(PTRS_PER_PGD)
+ */
+#if PGDIR_SHIFT + 9 < 63
+ decoy_addr = (pfn << PAGE_SHIFT) + (PAGE_OFFSET ^ BIT(63));
+#else
+#error "no unused virtual bit available"
+#endif
+
+ if (set_memory_np(decoy_addr, 1))
+ pr_warn("Could not invalidate pfn=0x%lx from 1:1 map\n", pfn);
+
+}
+#endif
+
/*
* The actual machine check handler. This only handles real
* exceptions when something got corrupted coming in through int 18.