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Hence use stac and clac instructions >> around access to the address to avoid triggering a >> LASS #GP fault. >> > > It seems we are implicitly relying on the on stac() and clac() calls > that are added for SMAP. Have you tried running with SMAP disabled  i.e > "clearcpuid=smap"? > Yes, I tested with clearcpuid=smap. > I believe there needs to be a dependency between LASS and SMAP. > Yes, In kernel mode, LASS depends on SMAP to work. And in user mode, it doesn't, so the dependency description in following may miss user space effect. > diff --git a/arch/x86/kernel/cpu/cpuid-deps.c > b/arch/x86/kernel/cpu/cpuid-deps.c > index d95221117129..00bc7e4a65d2 100644 > --- a/arch/x86/kernel/cpu/cpuid-deps.c > +++ b/arch/x86/kernel/cpu/cpuid-deps.c > @@ -79,6 +79,7 @@ static const struct cpuid_dep cpuid_deps[] = { >      { X86_FEATURE_XFD,            X86_FEATURE_XSAVES    }, >      { X86_FEATURE_XFD,            X86_FEATURE_XGETBV1   }, >      { X86_FEATURE_AMX_TILE,            X86_FEATURE_XFD       }, > +    { X86_FEATURE_LASS,            X86_FEATURE_SMAP      }, >      {} >  }; Thanks, Yian