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    Subject[tip:x86/pti] x86/entry/32: Unshare NMI return path
    Commit-ID:  8e676ced31e9d1448d3ffc4159586a259cc67f30
    Gitweb: https://git.kernel.org/tip/8e676ced31e9d1448d3ffc4159586a259cc67f30
    Author: Joerg Roedel <jroedel@suse.de>
    AuthorDate: Wed, 18 Jul 2018 11:40:42 +0200
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitDate: Fri, 20 Jul 2018 01:11:36 +0200

    x86/entry/32: Unshare NMI return path

    NMI will no longer use most of the shared return path, because NMI needs
    special handling when the CR3 switches for PTI are added. Prepare for that
    change.

    Signed-off-by: Joerg Roedel <jroedel@suse.de>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Tested-by: Pavel Machek <pavel@ucw.cz>
    Cc: "H . Peter Anvin" <hpa@zytor.com>
    Cc: linux-mm@kvack.org
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Dave Hansen <dave.hansen@intel.com>
    Cc: Josh Poimboeuf <jpoimboe@redhat.com>
    Cc: Juergen Gross <jgross@suse.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Jiri Kosina <jkosina@suse.cz>
    Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
    Cc: Brian Gerst <brgerst@gmail.com>
    Cc: David Laight <David.Laight@aculab.com>
    Cc: Denys Vlasenko <dvlasenk@redhat.com>
    Cc: Eduardo Valentin <eduval@amazon.com>
    Cc: Greg KH <gregkh@linuxfoundation.org>
    Cc: Will Deacon <will.deacon@arm.com>
    Cc: aliguori@amazon.com
    Cc: daniel.gruss@iaik.tugraz.at
    Cc: hughd@google.com
    Cc: keescook@google.com
    Cc: Andrea Arcangeli <aarcange@redhat.com>
    Cc: Waiman Long <llong@redhat.com>
    Cc: "David H . Gutteridge" <dhgutteridge@sympatico.ca>
    Cc: joro@8bytes.org
    Link: https://lkml.kernel.org/r/1531906876-13451-6-git-send-email-joro@8bytes.org

    ---
    arch/x86/entry/entry_32.S | 8 ++++++--
    1 file changed, 6 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
    index ef7d65315e8e..43641310b6e3 100644
    --- a/arch/x86/entry/entry_32.S
    +++ b/arch/x86/entry/entry_32.S
    @@ -1017,7 +1017,7 @@ ENTRY(nmi)

    /* Not on SYSENTER stack. */
    call do_nmi
    - jmp .Lrestore_all_notrace
    + jmp .Lnmi_return

    .Lnmi_from_sysenter_stack:
    /*
    @@ -1028,7 +1028,11 @@ ENTRY(nmi)
    movl PER_CPU_VAR(cpu_current_top_of_stack), %esp
    call do_nmi
    movl %ebx, %esp
    - jmp .Lrestore_all_notrace
    +
    +.Lnmi_return:
    + CHECK_AND_APPLY_ESPFIX
    + RESTORE_REGS 4
    + jmp .Lirq_return

    #ifdef CONFIG_X86_ESPFIX32
    .Lnmi_espfix_stack:
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