Re: [PATCH] x86/entry/64: Add an LFENCE after SAVE_AND_SET_GSBASE

> On Aug 20, 2020, at 02:15, Borislav Petkov wrote: > > From: Borislav Petkov > > The FSGSBASE macro to swap current GSBASE with the kernel GSBASE > probably had a speculation-stopping MSR write at some point but not > anymore. No, the macro has not any MSR write ever before. > diff --git a/

[PATCH] x86/entry/64: Add an LFENCE after SAVE_AND_SET_GSBASE

From: Borislav Petkov The FSGSBASE macro to swap current GSBASE with the kernel GSBASE probably had a speculation-stopping MSR write at some point but not anymore. Therefore, a fence is needed to stop speculation. Add it. Fixes: c82965f9e530 ("x86/entry/64: Handle FSGSBASE enabled paranoid ent