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Message-Id: <20220318143016.124387-6-jiangshanlai@gmail.com>
Date: Fri, 18 Mar 2022 22:30:14 +0800
From: Lai Jiangshan <jiangshanlai@...il.com>
To: linux-kernel@...r.kernel.org
Cc: Borislav Petkov <bp@...en8.de>,
Peter Zijlstra <peterz@...radead.org>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Andy Lutomirski <luto@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
Lai Jiangshan <jiangshan.ljs@...group.com>,
Ingo Molnar <mingo@...hat.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH V4 5/7] x86/entry: Don't call error_entry for XENPV
From: Lai Jiangshan <jiangshan.ljs@...group.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@...group.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
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