On Tue, Feb 27, 2024 at 09:19:13AM +0100, Jiri Slaby wrote: > On 27. 02. 24, 9:00, Pawan Gupta wrote: > > commit baf8361e54550a48a7087b603313ad013cc13386 upstream. > ... > > --- a/arch/x86/include/asm/nospec-branch.h > > +++ b/arch/x86/include/asm/nospec-branch.h > > @@ -194,6 +194,17 @@ > > #endif > > .endm > > +/* > > + * Macro to execute VERW instruction that mitigate transient data sampling > > + * attacks such as MDS. On affected systems a microcode update overloaded VERW > > + * instruction to also clear the CPU buffers. VERW clobbers CFLAGS.ZF. > > + * > > + * Note: Only the memory operand variant of VERW clears the CPU buffers. > > + */ > > +.macro CLEAR_CPU_BUFFERS > > + ALTERNATIVE "", __stringify(verw mds_verw_sel), X86_FEATURE_CLEAR_CPU_BUF > > The same here. Except 6.1 (I didn't check stable-6.1) does not have: > commit 270a69c4485d7d07516d058bcc0473c90ee22185 > Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Date: Wed Feb 8 18:10:52 2023 +0100 > > x86/alternative: Support relocations in alternatives > > yet. You likely need to backport that too. I will backport this patch too if rip-relative turns out to be a must. At this point, I am not sure if VERW buffer clearing behavior will be impacted by fixed addressing.
