Commit 0b2c605f authored by Borislav Petkov's avatar Borislav Petkov
Browse files

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: c82965f9 ("x86/entry/64: Handle FSGSBASE enabled paranoid entry/exit")
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200821090710.GE12181@zn.tnic
parent d012a719

arch/x86/entry/entry_64.S

+3 −2
Original line number Diff line number Diff line
@@ -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

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