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    SubjectRe: [Xen-devel] Re: [PATCH 0/6] xen: don't call vmalloc_sync_all() when mapping foreign pages
    On Wed, 21 Sep 2011, Jeremy Fitzhardinge wrote:
    > On 09/21/2011 03:42 AM, Stefano Stabellini wrote:
    > > On Thu, 15 Sep 2011, Jeremy Fitzhardinge wrote:
    > >> This series is relying on regular ram mappings are already synced to all
    > >> tasks, but I'm not sure that's necessarily guaranteed (for example, if
    > >> you hotplug new memory into the domain, the new pages won't be mapped
    > >> into every mm unless they're synced).
    > > the series is using GFP_KERNEL, so this problem shouldn't occur, right?
    > What properties do you think GFP_KERNEL guarantees?

    That the memory is below 4G and always mapped in the kernel 1:1 region.

    Regarding memory hotplug it looks like that x86_32 is mapping new memory
    ZONE_HIGHMEM, therefore avoiding any problems with GFP_KERNEL allocations.
    On the other hand x86_64 is mapping the memory ZONE_NORMAL and calling
    init_memory_mapping on the new range right away. AFAICT changes to
    the 1:1 mapping in init_mm are automatically synced across all mm's
    because the pgd is shared?

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      Last update: 2011-09-22 13:09    [W:0.019 / U:38.496 seconds]
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