lkml.org 
[lkml]   [2008]   [Jan]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH] [1/9] Handle kernel near memory hole in clear_kernel_mapping
    Date

    This was a long standing obscure problem in the relocatable kernel. The
    AMD GART driver needs to unmap part of the GART in the kernel direct mapping to
    prevent cache corruption. With the relocatable kernel it is in theory possible
    that the separate kernel text mapping straddles that area too.

    Normally it should not happen because GART tends to be >= 2GB, and the kernel
    is normally not loaded that high, but it is possible in theory.

    Teach clear_kernel_mapping() about this case.

    This will become more important once the kernel mapping uses 1GB pages.

    Cc: ebiederm@xmission.com
    Cc: vgoyal@redhat.com

    Signed-off-by: Andi Kleen <ak@suse.de>

    ---
    arch/x86/mm/init_64.c | 25 ++++++++++++++++++++++++-
    1 file changed, 24 insertions(+), 1 deletion(-)

    Index: linux/arch/x86/mm/init_64.c
    ===================================================================
    --- linux.orig/arch/x86/mm/init_64.c
    +++ linux/arch/x86/mm/init_64.c
    @@ -438,7 +438,8 @@ void __init paging_init(void)
    * address and size must be aligned to 2MB boundaries.
    * Does nothing when the mapping doesn't exist.
    */
    -void __init clear_kernel_mapping(unsigned long address, unsigned long size)
    +static void __init
    +__clear_kernel_mapping(unsigned long address, unsigned long size)
    {
    unsigned long end = address + size;

    @@ -475,6 +476,28 @@ void __init clear_kernel_mapping(unsigne
    __flush_tlb_all();
    }

    +#define overlaps(as, ae, bs, be) ((ae) >= (bs) && (as) <= (be))
    +
    +void __init clear_kernel_mapping(unsigned long address, unsigned long size)
    +{
    + int sh = PMD_SHIFT;
    + unsigned long kernel = __pa(__START_KERNEL_map);
    +
    + /*
    + * Note that we cannot unmap the kernel itself because the unmapped
    + * holes here are always at least 2MB aligned.
    + * This just applies to the trailing areas of the 40MB kernel mapping.
    + */
    + if (overlaps(kernel >> sh, (kernel + KERNEL_TEXT_SIZE) >> sh,
    + __pa(address) >> sh, __pa(address + size) >> sh)) {
    + printk(KERN_WARNING
    + "Kernel mapping at %lx within 2MB of memory hole\n",
    + kernel);
    + __clear_kernel_mapping(__START_KERNEL_map+__pa(address), size);
    + }
    + __clear_kernel_mapping(address, size);
    +}
    +
    /*
    * Memory hotplug specific functions
    */

    \
     
     \ /
      Last update: 2008-01-29 06:09    [W:0.023 / U:127.552 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site