KVM: x86: Snapshot the host's DEBUGCTL after disabling IRQs

Snapshot the host's DEBUGCTL after disabling IRQs, as perf can toggle
debugctl bits from IRQ context, e.g. when enabling/disabling events via
smp_call_function_single(). Taking the snapshot (long) before IRQs are
disabled could result in KVM effectively clobbering DEBUGCTL due to using
a stale snapshot.

Cc: [e-mail]
Reviewed-and-tested-by: Ravi Bangoria <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Sean Christopherson <[e-mail]>

arch/x86/kvm/x86.c

···
 
 	/* Save host pkru register if supported */
 	vcpu->arch.host_pkru = read_pkru();
-	vcpu->arch.host_debugctl = get_debugctlmsr();
 
 	/* Apply any externally detected TSC adjustments (due to suspend) */
 	if (unlikely(vcpu->arch.tsc_offset_adjustment)) {
···
 	} else if (unlikely(hw_breakpoint_active())) {
 		set_debugreg(0, 7);
 	}
+
+	vcpu->arch.host_debugctl = get_debugctlmsr();
 
 	guest_timing_enter_irqoff();