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    SubjectRe: [PATCH 24/35] arm64: mte: Switch GCR_EL1 in kernel entry and exit
    On Tue, Sep 08, 2020 at 03:58:07PM +0200, Andrey Konovalov wrote:
    > On Thu, Aug 27, 2020 at 12:38 PM Catalin Marinas
    > <catalin.marinas@arm.com> wrote:
    > >
    > > On Fri, Aug 14, 2020 at 07:27:06PM +0200, Andrey Konovalov wrote:
    > > > @@ -957,6 +984,7 @@ SYM_FUNC_START(cpu_switch_to)
    > > > mov sp, x9
    > > > msr sp_el0, x1
    > > > ptrauth_keys_install_kernel x1, x8, x9, x10
    > > > + mte_restore_gcr 1, x1, x8, x9
    > > > scs_save x0, x8
    > > > scs_load x1, x8
    > > > ret
    > >
    > > Since we set GCR_EL1 on exception entry and return, why is this needed?
    > > We don't have a per-kernel thread GCR_EL1, it's global to all threads,
    > > so I think cpu_switch_to() should not be touched.
    >
    > Dropping this line from the diff leads to many false-positives... I'll
    > leave this to Vincenzo.

    I wouldn't expect this to have any effect but maybe the
    mte_thread_switch() code still touches GCR_EL1 (it does this in the
    user-space support, Vincenzo's patches should move that to exception
    entry/return).

    --
    Catalin

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