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    SubjectRe: [PATCH v2 1/4] x86/hyper-v: move synic/stimer control structures definitions to hyperv-tlfs.h
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    On 27/11/18 19:48, Roman Kagan wrote:
    > On Tue, Nov 27, 2018 at 02:10:49PM +0100, Vitaly Kuznetsov wrote:
    >> Roman Kagan <rkagan@virtuozzo.com> writes:
    >>> On Mon, Nov 26, 2018 at 04:47:29PM +0100, Vitaly Kuznetsov wrote:
    >>> I personally tend to prefer masks over bitfields, so I'd rather do the
    >>> consolidation in the opposite direction: use the definitions in
    >>> hyperv-tlfs.h and replace those unions/bitfields elsewhere. (I vaguely
    >>> remember posting such a patchset a couple of years ago but I lacked the
    >>> motivation to complete it).
    >>
    >> Are there any known advantages of using masks over bitfields or the
    >> resulting binary code is the same?
    >
    > Strictly speaking bitwise ops are portable while bitfields are not, but
    > I guess this is not much of an issue with gcc which is dependable to
    > produce the right thing.
    >
    > I came to dislike the bitfields for the false feeling of atomicity of
    > assignment while most of the time they are read-modify-write operations.
    >
    > And no, I don't feel strong about it, so if nobody backs me on this I
    > give up :)

    I agree, but I am deferring to the Hyper-V maintainers. KVM is mostly
    reading these structs.

    Paolo

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