The following commit has been merged into the x86/cc branch of tip:
Commit-ID: 3f3d80f505f3d7273f374935558db5188acdd162
Gitweb: https://git.kernel.org/tip/3f3d80f505f3d7273f374935558db5188acdd162
Author: Nikolay Borisov <nik.borisov@xxxxxxxx>
AuthorDate: Wed, 29 May 2024 18:28:50 +03:00
Committer: Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Wed, 29 May 2024 17:53:57 +02:00
x86/kexec: Remove spurious unconditional JMP from from identity_mapped()
This seemingly straightforward JMP was introduced in the initial version
of the the 64bit kexec code without any explanation.
It turns out (check accompanying Link) it's likely a copy/paste artefact
from 32-bit code, where such a JMP could be used as a serializing
instruction for the 486's prefetch queue. On x86_64 that's not needed
because there's already a preceding write to cr4 which itself is
a serializing operation.
[ bp: Typos. Let's try this and see what cries out. If it does,
reverting it is trivial. ]
Signed-off-by: Nikolay Borisov <nik.borisov@xxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Link: https://lore.kernel.org/all/55bc0649-c017-49ab-905d-212f140a403f@xxxxxxxxxx/
---
arch/x86/kernel/relocate_kernel_64.S | 3 ---
1 file changed, 3 deletions(-)
diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
index 56cab1b..54e6200 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -153,9 +153,6 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
1:
movq %rax, %cr4
- jmp 1f
-1:
-
/* Flush the TLB (needed?) */
movq %r9, %cr3
|