On Tue, Mar 01, 2016 at 04:45:41PM -0800, Dave Hansen wrote: > >>> + WARN_ONCE((xfeatures_mask & XFEATURE_MASK_SUPERVISOR), > >>> + "x86/fpu: XSAVES supervisor states are not yet implemented.\n"); > >>> + > >>> cr4_set_bits(X86_CR4_OSXSAVE); > >>> xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask); > >>> } > >> > >> Let's also do a: > >> > >> xfeatures_mask &= ~XFEATURE_MASK_SUPERVISOR; > >> > >> Otherwise, we have a broken system at the moment. > >> > > Currently, if anyone sets any supervisor state in xfeatures_mask, the > > kernel prints out the warning then goes into a protection fault. > > That is a very strong indication to the user. Do we want to mute it? > > By "goes into a protection fault", do you mean that it doesn't boot? > > I'd just rather we put the kernel in a known-safe configuration (masking > supervisor state out of xfeatures_mask) rather than rely on the general > protection fault continuing to be generated by whatever is generating it. > Ok.
Yu-cheng
