The following commit has been merged into the x86/fsgsbase branch of tip:
Commit-ID: 0b2c605fa4ee3117c00b97b7af67791576b28f88
Gitweb: https://git.kernel.org/tip/0b2c605fa4ee3117c00b97b7af67791576b28f88
Author: Borislav Petkov <bp@xxxxxxx>
AuthorDate: Thu, 20 Aug 2020 11:10:15 +02:00
Committer: Borislav Petkov <bp@xxxxxxx>
CommitterDate: Mon, 24 Aug 2020 10:23:40 +02:00
x86/entry/64: Correct the comment over SAVE_AND_SET_GSBASE
Add the proper explanation why an LFENCE is not needed in the FSGSBASE
case.
Fixes: c82965f9e530 ("x86/entry/64: Handle FSGSBASE enabled paranoid entry/exit")
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Link: https://lkml.kernel.org/r/20200821090710.GE12181@xxxxxxx
---
arch/x86/entry/entry_64.S | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 70dea93..bf78de4 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -840,8 +840,9 @@ SYM_CODE_START_LOCAL(paranoid_entry)
* retrieve and set the current CPUs kernel GSBASE. The stored value
* has to be restored in paranoid_exit unconditionally.
*
- * The MSR write ensures that no subsequent load is based on a
- * mispredicted GSBASE. No extra FENCE required.
+ * The unconditional write to GS base below ensures that no subsequent
+ * loads based on a mispredicted GS base can happen, therefore no LFENCE
+ * is needed here.
*/
SAVE_AND_SET_GSBASE scratch_reg=%rax save_reg=%rbx
ret
|