On Thu, May 28, 2020 at 10:19:41PM +0200, Peter Zijlstra wrote: > static int arch_bp_generic_len(int x86_len) > --- a/arch/x86/kvm/vmx/nested.c > +++ b/arch/x86/kvm/vmx/nested.c > @@ -3027,6 +3027,8 @@ static int nested_vmx_check_vmentry_hw(s > > /* > * VMExit clears RFLAGS.IF and DR7, even on a consistency check. > + * XXX how is this not broken? access to cpu_dr7 ought to be with > + * IRQs disabled.
Ah, it's simply broken. This code is conditional on a module param that's off by default, i.e. it's not run widely, and odds are intersection with debugging is rare. Moving local_irq_enable() below the DR7 restoration is not an issue. Maybe also add lockdep_assert_irqs_disabled() to hw_breakpoint_restore() or hw_breakpoint_active()? > */ > local_irq_enable(); > if (hw_breakpoint_active()) > >
