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-rw-r--r--arch/x86/kernel/head64.c22
1 files changed, 20 insertions, 2 deletions
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 29ffa495bd1c..206a4b6144c2 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -222,13 +222,31 @@ unsigned long __head __startup_64(unsigned long physaddr,
* we might write invalid pmds, when the kernel is relocated
* cleanup_highmap() fixes this up along with the mappings
* beyond _end.
+ *
+ * Only the region occupied by the kernel image has so far
+ * been checked against the table of usable memory regions
+ * provided by the firmware, so invalidate pages outside that
+ * region. A page table entry that maps to a reserved area of
+ * memory would allow processor speculation into that area,
+ * and on some hardware (particularly the UV platform) even
+ * speculative access to some reserved areas is caught as an
+ * error, causing the BIOS to halt the system.
*/
pmd = fixup_pointer(level2_kernel_pgt, physaddr);
- for (i = 0; i < PTRS_PER_PMD; i++) {
+
+ /* invalidate pages before the kernel image */
+ for (i = 0; i < pmd_index((unsigned long)_text); i++)
+ pmd[i] &= ~_PAGE_PRESENT;
+
+ /* fixup pages that are part of the kernel image */
+ for (; i <= pmd_index((unsigned long)_end); i++)
if (pmd[i] & _PAGE_PRESENT)
pmd[i] += load_delta;
- }
+
+ /* invalidate pages after the kernel image */
+ for (; i < PTRS_PER_PMD; i++)
+ pmd[i] &= ~_PAGE_PRESENT;
/*
* Fixup phys_base - remove the memory encryption mask to obtain