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    SubjectRe: [PATCH v7 8/8] x86/tlb: just do tlb flush on one of siblings of SMT
    On 05/24/2012 11:03 PM, H. Peter Anvin wrote:

    > On 05/24/2012 07:32 AM, Alex Shi wrote:
    >>>
    >>> the TLB pool is shared as physical resource (dynamic or static, that
    >>> depends), but each tlb entry will be tagged for which of the two HT
    >>> pairs it's for, and on a logical level, they are completely separate as
    >>> a result (as they should be)
    >>
    >> But, why just flush part of SMT doesn't crash kernel on many benchmarks
    >> testing? Does it means flush tlb without PCID (doesn't enable in current
    >> kernel) will flush both of 'TLB pool'?
    >>
    >> Oh, lots of questions of the TLB pool details. :) Could you like share
    >> the URL of related documents?
    >>
    >
    > Hang on here... there is a huge difference between what a particular CPU
    > implementation does and what is architecturally guaranteed.
    >
    > Both wearing my Linux x86 maintainer hat, and wearing my Intel employee
    > hat, I want to categorically state that Linux cannot rely on behavior
    > that isn't architecturally guaranteed. Unless we can get an
    > architectural guarantee that this elision is safe, it cannot go in. It
    > doesn't work the other way -- the burden of proof is to prove that the
    > change is safe, not that the change cannot be proven unsafe.


    Understand and thanks for all of your time!

    >
    > -hpa
    >




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