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    SubjectRe: [PATCH 3/16] read/write_crX, clts and wbinvd for 64-bit paravirt
    Glauber de Oliveira Costa wrote:
    > I in fact have seen bugs with mixed reads and writes to the same cr,
    > (cr4), but adding the volatile
    > flag to the read function seemed to fix it.

    Well, volatile will make a read be repeated rather than caching the
    previous value, but it has no effect on ordering.

    > Yet, I agree with you that
    > the theorectical problem exists for the reorder, and your proposed fix
    > seems fine (although if we're really desperate about memory usage, we
    > can use a char instead a int and save 3 bytes!)

    Sure. Ideally the compiler would never even generate a reference to it,
    and it could just be extern, but in practice the compiler will generate
    references sometimes.

    J
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