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    SubjectRe: [PATCH 12/31] x86/entry/32: Add PTI cr3 switch to non-NMI entry/exit points
    On Thu, Mar 1, 2018 at 10:24 AM, Brian Gerst <brgerst@gmail.com> wrote:
    >
    > The IF flag only affects external maskable interrupts, not traps or
    > faults. You do need to check CR3 because SYSENTER does not clear TF
    > and will immediately cause a debug trap on kernel entry (with user
    > CR3) if set. That is why the code existed before to check for the
    > entry stack for debug/NMI.

    Note that debug traps can happen regardless of TF, Think kgdb etc.
    Arguably kgdb users get what they deserve, but still.. I think root
    can set kernel breakpoints too.

    Linus

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