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    SubjectRe: [PATCH v2 06/25] x86/xen: Add ANNOTATE_ENDBR to startup_xen()
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    On 19.04.22 13:57, Peter Zijlstra wrote:
    > On Tue, Apr 19, 2022 at 11:42:12AM +0000, Andrew Cooper wrote:
    >> On 18/04/2022 17:50, Josh Poimboeuf wrote:
    >>> The startup_xen() kernel entry point is referenced by the ".note.Xen"
    >>> section, but is presumably not indirect-branched to.
    >>
    >> It's the real entrypoint of the VM.  It's "got to" by setting %rip
    >> during vcpu setup.
    >>
    >> We could in principle support starting a PV VM with CET active, but that
    >> sounds like an enormous quantity of effort for very little gain.  CET
    >> for Xen PV requires paravirt anyway (because the kernel runs in CPL!=0)
    >> so decisions like this can wait until someone feels like doing the work.
    >>
    >>> Add ANNOTATE_ENDBR
    >>> to silence future objtool warnings.
    >>>
    >>> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
    >>> Cc: Juergen Gross <jgross@suse.com>
    >>> Cc: Stefano Stabellini <sstabellini@kernel.org>
    >>> Cc: xen-devel@lists.xenproject.org
    >>> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
    >>
    >> FWIW, Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>, preferably
    >> with the commit message tweaked to remove the uncertainty.
    >
    > Something like so then?
    >
    > ---
    > Subject: x86/xen: Add ANNOTATE_ENDBR to startup_xen()
    > From: Josh Poimboeuf <jpoimboe@redhat.com>
    > Date: Mon, 18 Apr 2022 09:50:25 -0700
    >
    > From: Josh Poimboeuf <jpoimboe@redhat.com>
    >
    > The startup_xen() kernel entry point is referenced by the ".note.Xen"
    > section, and is the real entry point of the VM. It *will* be
    > indirectly branched to, *however* currently Xen doesn't support PV VM
    > with CET active.

    Hmm, Xen will always use IRET to activate the guest.


    Juergen
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