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    Subject[PATCH 4.9 10/39] kaiser: fix regs to do_nmi() ifndef CONFIG_KAISER
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Hugh Dickins <hughd@google.com>


    pjt has observed that nmi's second (nmi_from_kernel) call to do_nmi()
    adjusted the %rdi regs arg, rightly when CONFIG_KAISER, but wrongly
    when not CONFIG_KAISER.

    Although the minimal change is to add an #ifdef CONFIG_KAISER around
    the addq line, that looks cluttered, and I prefer how the first call
    to do_nmi() handled it: prepare args in %rdi and %rsi before getting
    into the CONFIG_KAISER block, since it does not touch them at all.

    And while we're here, place the "#ifdef CONFIG_KAISER" that follows
    each, to enclose the "Unconditionally restore CR3" comment: matching
    how the "Unconditionally use kernel CR3" comment above is enclosed.

    Signed-off-by: Hugh Dickins <hughd@google.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/x86/entry/entry_64.S | 11 ++++++-----
    1 file changed, 6 insertions(+), 5 deletions(-)

    --- a/arch/x86/entry/entry_64.S
    +++ b/arch/x86/entry/entry_64.S
    @@ -1323,12 +1323,13 @@ ENTRY(nmi)
    movq %rax, %cr3
    #endif
    call do_nmi
    +
    +#ifdef CONFIG_KAISER
    /*
    * Unconditionally restore CR3. I know we return to
    * kernel code that needs user CR3, but do we ever return
    * to "user mode" where we need the kernel CR3?
    */
    -#ifdef CONFIG_KAISER
    popq %rax
    mov %rax, %cr3
    #endif
    @@ -1552,6 +1553,8 @@ end_repeat_nmi:
    SWAPGS
    xorl %ebx, %ebx
    1:
    + movq %rsp, %rdi
    + movq $-1, %rsi
    #ifdef CONFIG_KAISER
    /* Unconditionally use kernel CR3 for do_nmi() */
    /* %rax is saved above, so OK to clobber here */
    @@ -1564,16 +1567,14 @@ end_repeat_nmi:
    #endif

    /* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */
    - movq %rsp, %rdi
    - addq $8, %rdi /* point %rdi at ptregs, fixed up for CR3 */
    - movq $-1, %rsi
    call do_nmi
    +
    +#ifdef CONFIG_KAISER
    /*
    * Unconditionally restore CR3. We might be returning to
    * kernel code that needs user CR3, like just just before
    * a sysret.
    */
    -#ifdef CONFIG_KAISER
    popq %rax
    mov %rax, %cr3
    #endif

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