releases/3.14.16/x86-espfix-xen-fix-allocation-of-pages-for-paravirt-page-tables.patch

   1 From 8762e5092828c4dc0f49da5a47a644c670df77f3 Mon Sep 17 00:00:00 2001
   2 From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
   3 Date: Wed, 9 Jul 2014 13:18:18 -0400
   4 Subject: x86/espfix/xen: Fix allocation of pages for paravirt page tables
   5
   6 From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
   7
   8 commit 8762e5092828c4dc0f49da5a47a644c670df77f3 upstream.
   9
  10 init_espfix_ap() is currently off by one level when informing hypervisor
  11 that allocated pages will be used for ministacks' page tables.
  12
  13 The most immediate effect of this on a PV guest is that if
  14 'stack_page = __get_free_page()' returns a non-zeroed-out page the hypervisor
  15 will refuse to use it for a page table (which it shouldn't be anyway). This will
  16 result in warnings by both Xen and Linux.
  17
  18 More importantly, a subsequent write to that page (again, by a PV guest) is
  19 likely to result in fatal page fault.
  20
  21 Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
  22 Link: http://lkml.kernel.org/r/1404926298-5565-1-git-send-email-boris.ostrovsky@oracle.com
  23 Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
  24 Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
  25 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  26
  27 ---
  28  arch/x86/kernel/espfix_64.c |    5 ++---
  29  1 file changed, 2 insertions(+), 3 deletions(-)
  30
  31 --- a/arch/x86/kernel/espfix_64.c
  32 +++ b/arch/x86/kernel/espfix_64.c
  33 @@ -175,7 +175,7 @@ void init_espfix_ap(void)
  34         if (!pud_present(pud)) {
  35                 pmd_p = (pmd_t *)__get_free_page(PGALLOC_GFP);
  36                 pud = __pud(__pa(pmd_p) | (PGTABLE_PROT & ptemask));
  37 -               paravirt_alloc_pud(&init_mm, __pa(pmd_p) >> PAGE_SHIFT);
  38 +               paravirt_alloc_pmd(&init_mm, __pa(pmd_p) >> PAGE_SHIFT);
  39                 for (n = 0; n < ESPFIX_PUD_CLONES; n++)
  40                         set_pud(&pud_p[n], pud);
  41         }
  42 @@ -185,7 +185,7 @@ void init_espfix_ap(void)
  43         if (!pmd_present(pmd)) {
  44                 pte_p = (pte_t *)__get_free_page(PGALLOC_GFP);
  45                 pmd = __pmd(__pa(pte_p) | (PGTABLE_PROT & ptemask));
  46 -               paravirt_alloc_pmd(&init_mm, __pa(pte_p) >> PAGE_SHIFT);
  47 +               paravirt_alloc_pte(&init_mm, __pa(pte_p) >> PAGE_SHIFT);
  48                 for (n = 0; n < ESPFIX_PMD_CLONES; n++)
  49                         set_pmd(&pmd_p[n], pmd);
  50         }
  51 @@ -193,7 +193,6 @@ void init_espfix_ap(void)
  52         pte_p = pte_offset_kernel(&pmd, addr);
  53         stack_page = (void *)__get_free_page(GFP_KERNEL);
  54         pte = __pte(__pa(stack_page) | (__PAGE_KERNEL_RO & ptemask));
  55 -       paravirt_alloc_pte(&init_mm, __pa(stack_page) >> PAGE_SHIFT);
  56         for (n = 0; n < ESPFIX_PTE_CLONES; n++)
  57                 set_pte(&pte_p[n*PTE_STRIDE], pte);
  58