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    SubjectRe: [tip:x86/pti] x86/retpoline: Fill return stack buffer on vmexit
    On Sun, 14 Jan 2018, Borislav Petkov wrote:

    > On Fri, Jan 12, 2018 at 03:37:49AM -0800, tip-bot for David Woodhouse wrote:
    > > Commit-ID: 117cc7a908c83697b0b737d15ae1eb5943afe35b
    > > Gitweb: https://git.kernel.org/tip/117cc7a908c83697b0b737d15ae1eb5943afe35b
    > > Author: David Woodhouse <dwmw@amazon.co.uk>
    > > AuthorDate: Fri, 12 Jan 2018 11:11:27 +0000
    > > Committer: Thomas Gleixner <tglx@linutronix.de>
    > > CommitDate: Fri, 12 Jan 2018 12:33:37 +0100
    > >
    > > x86/retpoline: Fill return stack buffer on vmexit
    >
    > ...
    >
    > > + /*
    > > + * A simpler FILL_RETURN_BUFFER macro. Don't make people use the CPP
    > > + * monstrosity above, manually.
    > > + */
    > > +.macro FILL_RETURN_BUFFER reg:req nr:req ftr:req
    > > +#ifdef CONFIG_RETPOLINE
    > > + ANNOTATE_NOSPEC_ALTERNATIVE
    > > + ALTERNATIVE "jmp .Lskip_rsb_\@", \
    > > + __stringify(__FILL_RETURN_BUFFER(\reg,\nr,%_ASM_SP)) \
    > > + \ftr
    > > +.Lskip_rsb_\@:
    > > +#endif
    > > +.endm
    >
    > Looks unused to me. Was it ever gound to be used? If not:

    It's for the outstanding RSB fill after context switch.

    Thanks,

    tglx

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