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Subject[PATCH V7 5/6] 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 the CR3.

So there is no reason to call error_entry() in XENPV.

Cc: Juergen Gross <jgross@suse.com>
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 ab6ab6d3dab5..062aa9d95961 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -336,8 +336,17 @@ SYM_CODE_END(push_and_clear_regs)
call push_and_clear_regs
UNWIND_HINT_REGS

- call error_entry
- movq %rax, %rsp /* switch to the task stack if from userspace */
+ /*
+ * Call error_entry() and switch to the task stack if from userspace.
+ *
+ * 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 the 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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