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Subject[PATCH V6 28/49] x86/entry: Call paranoid_exit() in asm_exc_nmi()
Date
From: Lai Jiangshan <laijs@linux.alibaba.com>

The code between "call exc_nmi" and nmi_restore is as the same as
paranoid_exit(), so we can just use paranoid_exit() instead of the open
duplicated code.

No functional change intended.

Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
---
arch/x86/entry/entry_64.S | 34 +++++-----------------------------
1 file changed, 5 insertions(+), 29 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 897892dc563c..9fda034f3e92 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -957,8 +957,7 @@ SYM_CODE_END(paranoid_entry)

/*
* "Paranoid" exit path from exception stack. This is invoked
- * only on return from non-NMI IST interrupts that came
- * from kernel space.
+ * only on return from IST interrupts that came from kernel space.
*
* We may be returning to very strange contexts (e.g. very early
* in syscall entry), so checking for preemption here would
@@ -1306,11 +1305,7 @@ end_repeat_nmi:
pushq $-1 /* ORIG_RAX: no syscall to restart */

/*
- * Use paranoid_entry to handle SWAPGS, but no need to use paranoid_exit
- * as we should not be calling schedule in NMI context.
- * Even with normal interrupts enabled. An NMI should not be
- * setting NEED_RESCHED or anything that normal interrupts and
- * exceptions might do.
+ * Use paranoid_entry to handle SWAPGS and CR3.
*/
call paranoid_entry
UNWIND_HINT_REGS
@@ -1319,31 +1314,12 @@ end_repeat_nmi:
movq $-1, %rsi
call exc_nmi

- /* Always restore stashed CR3 value (see paranoid_entry) */
- RESTORE_CR3 scratch_reg=%r15 save_reg=%r14
-
/*
- * The above invocation of paranoid_entry stored the GSBASE
- * related information in R/EBX depending on the availability
- * of FSGSBASE.
- *
- * If FSGSBASE is enabled, restore the saved GSBASE value
- * unconditionally, otherwise take the conditional SWAPGS path.
+ * Use paranoid_exit to handle SWAPGS and CR3, but no need to use
+ * restore_regs_and_return_to_kernel as we must handle nested NMI.
*/
- ALTERNATIVE "jmp nmi_no_fsgsbase", "", X86_FEATURE_FSGSBASE
-
- wrgsbase %rbx
- jmp nmi_restore
-
-nmi_no_fsgsbase:
- /* EBX == 0 -> invoke SWAPGS */
- testl %ebx, %ebx
- jnz nmi_restore
-
-nmi_swapgs:
- swapgs
+ call paranoid_exit

-nmi_restore:
POP_REGS

/*
--
2.19.1.6.gb485710b
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