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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@linutronix.de>
AuthorDate: Thu, 21 May 2020 22:05:30 +02:00
Committer: Ingo Molnar <mingo@kernel.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@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Andy Lutomirski <luto@kernel.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 */

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