Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[sfrench/cifs-2.6.git] / arch / x86 / kernel / head64.c

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 29ffa495bd1cb7333b77e33aa80a055ec0ec6d69..206a4b6144c2e1d9a0780a82424c4817bf390d7d 100644 (file)
--- 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