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    SubjectRe: [RFC][PATCH resend 8/12] asm-generic: bitops: introduce le bit offset macro
    On Tue, 04 May 2010 19:08:23 +0300
    Avi Kivity <> wrote:

    > On 05/04/2010 06:03 PM, Arnd Bergmann wrote:
    > > On Tuesday 04 May 2010, Takuya Yoshikawa wrote:
    > >> So let us use the le bit offset calculation part by defining it as a new
    > >> macro: generic_le_bit_offset() .
    > >>
    > > Does this work correctly if your user space is 32 bits (i.e. unsigned long
    > > is different size in user space and kernel) in both big- and little-endian
    > > systems?
    > >
    > > I'm not sure about all the details, but I think you cannot in general share
    > > bitmaps between user space and kernel because of this.
    > >
    > That's why the bitmaps are defined as little endian u64 aligned, even on
    > big endian 32-bit systems. Little endian bitmaps are wordsize agnostic,
    > and u64 alignment ensures we can use long-sized bitops on mixed size
    > systems.

    There was a suggestion to propose set_le_bit_user() kind of macros.
    But what I thought was these have a constraint you two explained and seemed to be
    a little bit specific to some area, like KVM.

    So I decided to propose just the offset calculation macro.

    Thanks, Takuya

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