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    SubjectRe: [Xen-devel] [PATCH] xen: grant-table: Check truncation when giving access to a frame
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    Hi David,

    On 13/06/16 11:57, David Vrabel wrote:
    > On 13/06/16 11:50, Julien Grall wrote:
    >> The version 1 of the grant-table protocol only supports frame encoded on
    >> 32-bit.
    >>
    >> When the platform is supporting 48-bit physical address, the frame will
    >> be encoded on 36-bit which will lead a truncation and give access to
    >> the wrong frame.
    >>
    >> On ARM Xen will always allow the guest to use all the physical address,
    >> although today the RAM is always located under 40-bits (see
    >> xen/include/public/arch-arm.h).
    >>
    >> Add a truncation check in gnttab_update_entry_v1 to prevent the guest to
    >> give access to the wrong frame.
    >
    > In hindsight, we shouldn't have dropped the V2 support from Linux.
    > Should we reinstate it?

    What were the reasons to drop the v2 support from Linux? More
    importantly why people did choose to stay on v1?

    Cheers,

    --
    Julien Grall

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