On 6/20/25 16:08, Andrew Cooper wrote: >> But, the resulting code is wonky. It needs to do something more like this: >> >> if ((error_code & (X86_PF_WRITE | X86_PF_USER)) != X86_PF_USER) >> return false; >> >> if (error_code & X86_PF_INSTR)) >> return __emulate_vsyscall(regs, address); > To do this, LASS needs a proper interlink against NX || SMEP. > > If neither NX nor SMEP are active, the CPU does not report X86_PF_INSTR, > meaning that fetches are reported as plain reads. Interesting point. I think the easiest way to do this is just make a cpuid_deps[] entry for LASS and NX. If there's a CPU where LASS is available but where NX isn't available, we have much bigger problems on our hands.
