linux-kernel - [tip: x86/entry] x86/entry: Change exit path of xen_failsafe

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Message-ID: <159056711406.17951.18444151600925271077.tip-bot2@tip-bot2>
Date:   Wed, 27 May 2020 08:11:54 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Andy Lutomirski <luto@...nel.org>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: x86/entry] x86/entry: Change exit path of xen_failsafe_callback

The following commit has been merged into the x86/entry branch of tip:

Commit-ID:     c8af31cbb0650b2be9b6a2a9cdb3a2a0770d7417
Gitweb:        https://git.kernel.org/tip/c8af31cbb0650b2be9b6a2a9cdb3a2a0770d7417
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Thu, 21 May 2020 22:05:30 +02:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Tue, 26 May 2020 19:06:28 +02:00

x86/entry: Change exit path of xen_failsafe_callback

xen_failsafe_callback() is invoked from XEN for two cases:

  1. Fault while reloading DS, ES, FS or GS
  2. Fault while executing IRET

 #1 retries the IRET after XEN has fixed up the segments.
 #2 injects a #GP which kills the task

For #1 there is no reason to go through the full exception return path
because the tasks TIF state is still the same. So just going straight to
the IRET path is good enough.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Acked-by: Andy Lutomirski <luto@...nel.org>
Link: https://lore.kernel.org/r/20200521202118.423224507@linutronix.de
---
 arch/x86/entry/entry_32.S | 2 +-
 arch/x86/entry/entry_64.S | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 8b29330..bd25706 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -1352,7 +1352,7 @@ SYM_FUNC_START(xen_failsafe_callback)
 5:	pushl	$-1				/* orig_ax = -1 => not a system call */
 	SAVE_ALL
 	ENCODE_FRAME_POINTER
-	jmp	ret_from_exception
+	jmp	handle_exception_return
 
 .section .fixup, "ax"
 6:	xorl	%eax, %eax
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 2e476f4..a526fb5 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1175,7 +1175,7 @@ SYM_CODE_START(xen_failsafe_callback)
 	pushq	$-1 /* orig_ax = -1 => not a system call */
 	PUSH_AND_CLEAR_REGS
 	ENCODE_FRAME_POINTER
-	jmp	error_exit
+	jmp	error_return
 SYM_CODE_END(xen_failsafe_callback)
 #endif /* CONFIG_XEN_PV */