[Xen-changelog] [xen master] x86/idle: Clear SPEC_CTRL while idle

[patchbot@xxxxxxx]

*** New tip has no discernable common ancestor with previous history ***
    Previously reported histories end at:
        e01fa4e223fc077e18936d890dbd4813c3e7c9b1
        3a28f760508fb35c430edac17a9efde5aff6d1d5
        123c7793797502b222300eb710cd3873dcca41ee
        c40317f11b3f05e7c06a2213560c8471081f2662
        a6f2cdb633bf519244a16674031b8034b581ba7f
        8e4b2676685f50bc26f03b5f62d8b7aea8e69dbf
        2f5af2c962c05b789bdd65b46c74711e903f86d0
        695bb5f504ab48c1d546446f104c1b6c0ead126d
        9053a74c08fd6abf43bb45ff932b4386de7e8510
        16b1414de91b5a82a0996c67f6db3af7d7e32873
        572a78190403e5f2acbd01fa72c35fafe9700169
        e871e80c38547d9faefc6604532ba3e985e65873

commit 4c7e478d597b0346eef3a256cfd6794ac778b608
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Fri Nov 3 16:43:02 2017 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Fri Jan 26 14:10:21 2018 +0000

    x86/idle: Clear SPEC_CTRL while idle
    
    On contemporary hardware, setting IBRS/STIBP has a performance impact on
    adjacent hyperthreads.  It is therefore recommended to clear the setting
    before becoming idle, to avoid an idle core preventing adjacent userspace
    execution from running at full performance.
    
    Care must be taken to ensure there are no ret or indirect branch 
instructions
    between spec_ctrl_{enter,exit}_idle() invocations, which are forced always
    inline.  Care must also be taken to avoid using spec_ctrl_enter_idle() 
between
    flushing caches and becoming idle, in cases where that matters.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
--
generated by git-patchbot for /home/xen/git/xen.git#master

_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/xen-changelog