From 0b2c605fa4ee3117c00b97b7af67791576b28f88 Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Thu, 20 Aug 2020 11:10:15 +0200 Subject: [PATCH] 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 Link: https://lkml.kernel.org/r/20200821090710.GE12181@zn.tnic --- 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 70dea9337816..bf78de4de7f0 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