On 3/29/21 2:55 PM, Kuppuswamy, Sathyanarayanan wrote: >> >> MONITOR is a privileged instruction, right? So we can only end up in >> here if the kernel screws up and isn't reading CPUID correctly, right? >> >> That dosen't seem to me like something we want to suppress. This needs >> a warning, at least. I assume that having a MONITOR instruction >> immediately return doesn't do any harm. > Agree. Since we are not supposed to come here, I will use BUG.
"This is unexpected" is a WARN()able offense. "This is unexpected and might be corrupting data" is where we want to use BUG(). Does broken MONITOR risk data corruption? >>> + case EXIT_REASON_MWAIT_INSTRUCTION: >>> + /* MWAIT is supressed, not supposed to reach here. */ >>> + WARN(1, "MWAIT unexpected #VE Exception\n"); >>> + return -EFAULT; >> >> How is MWAIT "supppressed"? > I am clearing the MWAIT feature flag in early init code. We should also > disable this feature in firmware. setup_clear_cpu_cap(X86_FEATURE_MWAIT); I'd be more explicit about that. Maybe even reference the code that clears the X86_FEATURE.
