On Thu, 2023-09-14 at 02:33 -0400, Yang Weijiang wrote: > fpu_kernel_dynamic_xfeatures now are __ONLY__ enabled by guest kernel and > used for guest fpstate, i.e., none for normal fpstate. The bits are added > when guest fpstate is allocated and fpstate->is_guest set to %true. > > For normal fpstate, the bits should have been removed when init system FPU > settings, WARN_ONCE() if normal fpstate contains kernel dynamic xfeatures > before xsaves is executed. > > Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx> > --- > arch/x86/kernel/fpu/xstate.h | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h > index 9c6e3ca05c5c..c2b33a5db53d 100644 > --- a/arch/x86/kernel/fpu/xstate.h > +++ b/arch/x86/kernel/fpu/xstate.h > @@ -186,6 +186,9 @@ static inline void os_xsave(struct fpstate *fpstate) > WARN_ON_FPU(!alternatives_patched); > xfd_validate_state(fpstate, mask, false); > > + WARN_ON_FPU(!fpstate->is_guest && > + (mask & fpu_kernel_dynamic_xfeatures)); > + > XSTATE_XSAVE(&fpstate->regs.xsave, lmask, hmask, err); > > /* We should never fault when copying to a kernel buffer: */ I am not sure about this patch. It's true that now the kernel dynamic features are for guest only, but in the future I can easily see a kernel dynamic feature that will also be used in the kernel itself. Maybe we can add a comment above this warning to say that _currently_ there are no kernel dynamic features that are enabled for the host kernel. Best regards, Maxim Levitsky
