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    SubjectRE: Fw: [PATCH] ia64: race flushing icache in do_no_page path
     Hi Hugh,

    -----Original Message-----
    From: Hugh Dickins []
    Sent: Friday, April 27, 2007 10:34 PM
    To: Rohit Seth
    Cc: Nick Piggin; Mike Stroyan; Andrew Morton; Luck, Tony;;
    Subject: Re: Fw: [PATCH] ia64: race flushing icache in do_no_page path

    On Fri, 27 Apr 2007, Rohit Seth wrote:

    > lazy_mmu_prot_update was added specifically for notifying change in
    > protection. So, in a way it is closer to update_mmu_cache (Which is
    > for change in mappings itself). Though for ia64 implementation, this
    > ends up flushing the icaches when needed.

    >The ia64 implementation is the only one which has any use for it,

    Even Itanium didn't need it for almost 5 years :) Though I think archs that
    have incoherent I & D caches could be (theoritically) exposed to same
    (original) mprotect code path bug that triggered this API.

    >it's only interested when it's executable i.e. "lazy_mmu_prot_update"
    >is a name concealing some overdesign.

    You are right that ia64 is only interested in whne the execute permissions
    kick in (and FWIW ia64 used to use update_mmu_cache API to do what it is now
    doing lazy_mmu_prot_update). Though the idea was to design an API that any
    arch can use to know when ever there is change in protections on a mapping.


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