lkml.org 
[lkml]   [2014]   [Sep]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Date
    Subject[PATCH 3.2 130/131] x86/espfix/xen: Fix allocation of pages for paravirt page tables
    3.2.63-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Boris Ostrovsky <boris.ostrovsky@oracle.com>

    commit 8762e5092828c4dc0f49da5a47a644c670df77f3 upstream.

    init_espfix_ap() is currently off by one level when informing hypervisor
    that allocated pages will be used for ministacks' page tables.

    The most immediate effect of this on a PV guest is that if
    'stack_page = __get_free_page()' returns a non-zeroed-out page the hypervisor
    will refuse to use it for a page table (which it shouldn't be anyway). This will
    result in warnings by both Xen and Linux.

    More importantly, a subsequent write to that page (again, by a PV guest) is
    likely to result in fatal page fault.

    Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
    Link: http://lkml.kernel.org/r/1404926298-5565-1-git-send-email-boris.ostrovsky@oracle.com
    Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    arch/x86/kernel/espfix_64.c | 5 ++---
    1 file changed, 2 insertions(+), 3 deletions(-)

    --- a/arch/x86/kernel/espfix_64.c
    +++ b/arch/x86/kernel/espfix_64.c
    @@ -175,7 +175,7 @@ void init_espfix_ap(void)
    if (!pud_present(pud)) {
    pmd_p = (pmd_t *)__get_free_page(PGALLOC_GFP);
    pud = __pud(__pa(pmd_p) | (PGTABLE_PROT & ptemask));
    - paravirt_alloc_pud(&init_mm, __pa(pmd_p) >> PAGE_SHIFT);
    + paravirt_alloc_pmd(&init_mm, __pa(pmd_p) >> PAGE_SHIFT);
    for (n = 0; n < ESPFIX_PUD_CLONES; n++)
    set_pud(&pud_p[n], pud);
    }
    @@ -185,7 +185,7 @@ void init_espfix_ap(void)
    if (!pmd_present(pmd)) {
    pte_p = (pte_t *)__get_free_page(PGALLOC_GFP);
    pmd = __pmd(__pa(pte_p) | (PGTABLE_PROT & ptemask));
    - paravirt_alloc_pmd(&init_mm, __pa(pte_p) >> PAGE_SHIFT);
    + paravirt_alloc_pte(&init_mm, __pa(pte_p) >> PAGE_SHIFT);
    for (n = 0; n < ESPFIX_PMD_CLONES; n++)
    set_pmd(&pmd_p[n], pmd);
    }
    @@ -193,7 +193,6 @@ void init_espfix_ap(void)
    pte_p = pte_offset_kernel(&pmd, addr);
    stack_page = (void *)__get_free_page(GFP_KERNEL);
    pte = __pte(__pa(stack_page) | (__PAGE_KERNEL_RO & ptemask));
    - paravirt_alloc_pte(&init_mm, __pa(stack_page) >> PAGE_SHIFT);
    for (n = 0; n < ESPFIX_PTE_CLONES; n++)
    set_pte(&pte_p[n*PTE_STRIDE], pte);



    \
     
     \ /
      Last update: 2014-09-11 15:01    [W:4.157 / U:0.688 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site