kaiser: fix regs to do_nmi() ifndef CONFIG_KAISER

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>
Gbp-Pq: Topic features/all/kpti
Gbp-Pq: Name kaiser-fix-regs-to-do_nmi-ifndef-config_kaiser.patch

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 5874e3280135b47480924f99c80e92149fd4bb98..2f9eb09210a3fe237444a80809c427b363ad4e66 100644 (file)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1337,12 +1337,13 @@ 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
@@ -1566,6 +1567,8 @@ 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 */
@@ -1578,16 +1581,14 @@ 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