lkml.org 
[lkml]   [2022]   [Mar]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH V4 5/7] x86/entry: Don't call error_entry for XENPV
Date
From: Lai Jiangshan <jiangshan.ljs@antgroup.com>

When in XENPV, it is already in the task stack, and it can't fault
for native_iret() nor native_load_gs_index() since XENPV uses its own
pvops for iret and load_gs_index(). And it doesn't need to switch CR3.
So there is no reason to call error_entry() in XENPV.

Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
---
arch/x86/entry/entry_64.S | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 8121b9f3fceb..e9fe9f00d17c 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -328,8 +328,17 @@ SYM_CODE_END(ret_from_fork)
PUSH_AND_CLEAR_REGS
ENCODE_FRAME_POINTER

- call error_entry
- movq %rax, %rsp /* switch stack settled by sync_regs() */
+ /*
+ * Call error_entry and switch stack settled by sync_regs().
+ *
+ * When in XENPV, it is already in the task stack, and it can't fault
+ * for native_iret() nor native_load_gs_index() since XENPV uses its
+ * own pvops for iret and load_gs_index(). And it doesn't need to
+ * switch CR3. So it can skip invoking error_entry().
+ */
+ ALTERNATIVE "call error_entry; movq %rax, %rsp", \
+ "", X86_FEATURE_XENPV
+
ENCODE_FRAME_POINTER
UNWIND_HINT_REGS

--
2.19.1.6.gb485710b
\
 
 \ /
  Last update: 2022-09-17 16:18    [W:1.897 / U:0.008 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site