Re: [PATCH v2 2/3] x86/entry/64: Use the TSS sp2 slot for SYSCALL/SYSRET scratch space

[Borislav Petkov]

On Mon, Sep 03, 2018 at 03:59:43PM -0700, Andy Lutomirski wrote:
> In the non-trampoline SYSCALL64 path, we use a percpu variable to
> temporarily store the user RSP value.  Instead of a separate
> variable, use the otherwise unused sp2 slot in the TSS.  This will
> improve cache locality, as the sp1 slot is already used in the same
> code to find the kernel stack.  It will also simplify a future
> change to make the non-trampoline path work in PTI mode.
> 
> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
> ---
>  arch/x86/entry/entry_64.S        | 16 +++++++++-------
>  arch/x86/include/asm/processor.h |  6 ++++++
>  arch/x86/kernel/asm-offsets.c    |  3 ++-
>  arch/x86/kernel/process_64.c     |  2 --
>  arch/x86/xen/xen-asm_64.S        |  8 +++++---
>  5 files changed, 22 insertions(+), 13 deletions(-)

Reviewed-by: Borislav Petkov <bp@xxxxxxx>

-- 
Regards/Gruss,
    Boris.

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