linux-kernel - [PATCH 4.1 32/65] kaiser: fix regs to do_nmi() ifndef CONFIG

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Message-Id: <20180306002538.1761-33-pasha.tatashin@oracle.com>
Date:   Mon,  5 Mar 2018 19:25:05 -0500
From:   Pavel Tatashin <pasha.tatashin@...cle.com>
To:     steven.sistare@...cle.com, daniel.m.jordan@...cle.com,
        linux-kernel@...r.kernel.org, Alexander.Levin@...rosoft.com,
        dan.j.williams@...el.com, sathyanarayanan.kuppuswamy@...el.com,
        pankaj.laxminarayan.bharadiya@...el.com, akuster@...sta.com,
        cminyard@...sta.com, pasha.tatashin@...cle.com,
        gregkh@...uxfoundation.org, stable@...r.kernel.org
Subject: [PATCH 4.1 32/65] kaiser: fix regs to do_nmi() ifndef CONFIG_KAISER

From: Hugh Dickins <hughd@...gle.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@...gle.com>
Acked-by: Jiri Kosina <jkosina@...e.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
(cherry picked from commit 487f0b73d82611a2dc48d7d78409e2e9d994006a)
Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>

Conflicts:
	arch/x86/entry/entry_64.S (not in this tree)
	arch/x86/kernel/entry_64.S (patched instead of that)
---
 arch/x86/kernel/entry_64.S | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 1bda5ebd1013..8e4056d4b1d6 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1547,12 +1547,12 @@ 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
@@ -1772,6 +1772,8 @@ 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 */
@@ -1785,16 +1787,13 @@ end_repeat_nmi:
 	DEFAULT_FRAME 0				/* XXX: Do we need this? */
 
 	/* 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
-- 
2.16.2