This is a note to let you know that I've just added the patch titled
x86/entry: Don't call error_entry() for XENPV
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-entry-don-t-call-error_entry-for-xenpv.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Tue Jul 12 05:06:57 PM CEST 2022
From: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx>
Date: Tue, 3 May 2022 11:21:06 +0800
Subject: x86/entry: Don't call error_entry() for XENPV
From: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx>
commit 64cbd0acb58203fb769ed2f4eab526d43e243847 upstream.
XENPV guests enter already on the task stack and they can't fault for
native_iret() nor native_load_gs_index() since they use their own pvop
for IRET and load_gs_index(). A CR3 switch is not needed either.
So there is no reason to call error_entry() in XENPV.
[ bp: Massage commit message. ]
Signed-off-by: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
Link: https://lore.kernel.org/r/20220503032107.680190-6-jiangshanlai@xxxxxxxxx
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/entry/entry_64.S | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -333,8 +333,17 @@ 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
Patches currently in stable-queue which might be from jiangshan.ljs@xxxxxxxxxxxx are
queue-5.15/x86-entry-move-push_and_clear_regs-out-of-error_entry.patch
queue-5.15/x86-entry-switch-the-stack-after-error_entry-returns.patch
queue-5.15/x86-entry-don-t-call-error_entry-for-xenpv.patch
queue-5.15/x86-traps-use-pt_regs-directly-in-fixup_bad_iret.patch
