KVM: x86: Don't report guest userspace emulation error to userspace

Commit fc3a9157d314 ("KVM: X86: Don't report L2 emulation failures to
user-space") disabled the reporting of L2 (nested guest) emulation failures to
userspace due to race-condition between a vmexit and the instruction emulator.
The same rational applies also to userspace applications that are permitted by
the guest OS to access MMIO area or perform PIO.

This patch extends the current behavior - of injecting a #UD instead of
reporting it to userspace - also for guest userspace code.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
static int kvm_guest_time_update(struct kvm_vcpu *v)
{
	unsigned long flags, this_tsc_khz;
	struct kvm_vcpu_arch *vcpu = &v->arch;
	struct kvm_arch *ka = &v->kvm->arch;
	s64 kernel_ns;
	u64 tsc_timestamp, host_tsc;
	struct pvclock_vcpu_time_info guest_hv_clock;
	u8 pvclock_flags;
	bool use_master_clock;

	kernel_ns = 0;
	host_tsc = 0;

	/*
	 * If the host uses TSC clock, then passthrough TSC as stable
	 * to the guest.
	 */
	spin_lock(&ka->pvclock_gtod_sync_lock);
	use_master_clock = ka->use_master_clock;
	if (use_master_clock) {
		host_tsc = ka->master_cycle_now;
		kernel_ns = ka->master_kernel_ns;
	}
	spin_unlock(&ka->pvclock_gtod_sync_lock);

	/* Keep irq disabled to prevent changes to the clock */
	local_irq_save(flags);
	this_tsc_khz = __get_cpu_var(cpu_tsc_khz);
	if (unlikely(this_tsc_khz == 0)) {
		local_irq_restore(flags);
		kvm_make_request(KVM_REQ_CLOCK_UPDATE, v);
		return 1;
	}
	if (!use_master_clock) {
		host_tsc = native_read_tsc();
		kernel_ns = get_kernel_ns();
	}

	tsc_timestamp = kvm_x86_ops->read_l1_tsc(v, host_tsc);

	/*
	 * We may have to catch up the TSC to match elapsed wall clock
	 * time for two reasons, even if kvmclock is used.
	 *   1) CPU could have been running below the maximum TSC rate
	 *   2) Broken TSC compensation resets the base at each VCPU
	 *      entry to avoid unknown leaps of TSC even when running
	 *      again on the same CPU.  This may cause apparent elapsed
	 *      time to disappear, and the guest to stand still or run
	 *	very slowly.
	 */
	if (vcpu->tsc_catchup) {
		u64 tsc = compute_guest_tsc(v, kernel_ns);
		if (tsc > tsc_timestamp) {
			adjust_tsc_offset_guest(v, tsc - tsc_timestamp);
			tsc_timestamp = tsc;
		}
	}

	local_irq_restore(flags);

	if (!vcpu->pv_time_enabled)
		return 0;

	if (unlikely(vcpu->hw_tsc_khz != this_tsc_khz)) {
		kvm_get_time_scale(NSEC_PER_SEC / 1000, this_tsc_khz,
				   &vcpu->hv_clock.tsc_shift,
				   &vcpu->hv_clock.tsc_to_system_mul);
		vcpu->hw_tsc_khz = this_tsc_khz;
	}

	/* With all the info we got, fill in the values */
	vcpu->hv_clock.tsc_timestamp = tsc_timestamp;
	vcpu->hv_clock.system_time = kernel_ns + v->kvm->arch.kvmclock_offset;
	vcpu->last_guest_tsc = tsc_timestamp;

	/*
	 * The interface expects us to write an even number signaling that the
	 * update is finished. Since the guest won't see the intermediate
	 * state, we just increase by 2 at the end.
	 */
	vcpu->hv_clock.version += 2;

	if (unlikely(kvm_read_guest_cached(v->kvm, &vcpu->pv_time,
		&guest_hv_clock, sizeof(guest_hv_clock))))
		return 0;

	/* retain PVCLOCK_GUEST_STOPPED if set in guest copy */
	pvclock_flags = (guest_hv_clock.flags & PVCLOCK_GUEST_STOPPED);

	if (vcpu->pvclock_set_guest_stopped_request) {
		pvclock_flags |= PVCLOCK_GUEST_STOPPED;
		vcpu->pvclock_set_guest_stopped_request = false;
	}

	/* If the host uses TSC clocksource, then it is stable */
	if (use_master_clock)
		pvclock_flags |= PVCLOCK_TSC_STABLE_BIT;

	vcpu->hv_clock.flags = pvclock_flags;

	kvm_write_guest_cached(v->kvm, &vcpu->pv_time,
				&vcpu->hv_clock,
				sizeof(vcpu->hv_clock));
	return 0;
}

static int kvm_guest_time_update(struct kvm_vcpu *v)
{
	unsigned long flags, this_tsc_khz;
	struct kvm_vcpu_arch *vcpu = &v->arch;
	struct kvm_arch *ka = &v->kvm->arch;
	s64 kernel_ns;
	u64 tsc_timestamp, host_tsc;
	struct pvclock_vcpu_time_info guest_hv_clock;
	u8 pvclock_flags;
	bool use_master_clock;

	kernel_ns = 0;
	host_tsc = 0;

	/*
	 * If the host uses TSC clock, then passthrough TSC as stable
	 * to the guest.
	 */
	spin_lock(&ka->pvclock_gtod_sync_lock);
	use_master_clock = ka->use_master_clock;
	if (use_master_clock) {
		host_tsc = ka->master_cycle_now;
		kernel_ns = ka->master_kernel_ns;
	}
	spin_unlock(&ka->pvclock_gtod_sync_lock);

	/* Keep irq disabled to prevent changes to the clock */
	local_irq_save(flags);
	this_tsc_khz = __get_cpu_var(cpu_tsc_khz);
	if (unlikely(this_tsc_khz == 0)) {
		local_irq_restore(flags);
		kvm_make_request(KVM_REQ_CLOCK_UPDATE, v);
		return 1;
	}
	if (!use_master_clock) {
		host_tsc = native_read_tsc();
		kernel_ns = get_kernel_ns();
	}

	tsc_timestamp = kvm_x86_ops->read_l1_tsc(v, host_tsc);

	/*
	 * We may have to catch up the TSC to match elapsed wall clock
	 * time for two reasons, even if kvmclock is used.
	 *   1) CPU could have been running below the maximum TSC rate
	 *   2) Broken TSC compensation resets the base at each VCPU
	 *      entry to avoid unknown leaps of TSC even when running
	 *      again on the same CPU.  This may cause apparent elapsed
	 *      time to disappear, and the guest to stand still or run
	 *	very slowly.
	 */
	if (vcpu->tsc_catchup) {
		u64 tsc = compute_guest_tsc(v, kernel_ns);
		if (tsc > tsc_timestamp) {
			adjust_tsc_offset_guest(v, tsc - tsc_timestamp);
			tsc_timestamp = tsc;
		}
	}

	local_irq_restore(flags);

	if (!vcpu->pv_time_enabled)
		return 0;

	if (unlikely(vcpu->hw_tsc_khz != this_tsc_khz)) {
		kvm_get_time_scale(NSEC_PER_SEC / 1000, this_tsc_khz,
				   &vcpu->hv_clock.tsc_shift,
				   &vcpu->hv_clock.tsc_to_system_mul);
		vcpu->hw_tsc_khz = this_tsc_khz;
	}

	/* With all the info we got, fill in the values */
	vcpu->hv_clock.tsc_timestamp = tsc_timestamp;
	vcpu->hv_clock.system_time = kernel_ns + v->kvm->arch.kvmclock_offset;
	vcpu->last_guest_tsc = tsc_timestamp;

	/*
	 * The interface expects us to write an even number signaling that the
	 * update is finished. Since the guest won't see the intermediate
	 * state, we just increase by 2 at the end.
	 */
	vcpu->hv_clock.version += 2;

	if (unlikely(kvm_read_guest_cached(v->kvm, &vcpu->pv_time,
		&guest_hv_clock, sizeof(guest_hv_clock))))
		return 0;

	/* retain PVCLOCK_GUEST_STOPPED if set in guest copy */
	pvclock_flags = (guest_hv_clock.flags & PVCLOCK_GUEST_STOPPED);

	if (vcpu->pvclock_set_guest_stopped_request) {
		pvclock_flags |= PVCLOCK_GUEST_STOPPED;
		vcpu->pvclock_set_guest_stopped_request = false;
	}

	/* If the host uses TSC clocksource, then it is stable */
	if (use_master_clock)
		pvclock_flags |= PVCLOCK_TSC_STABLE_BIT;

	vcpu->hv_clock.flags = pvclock_flags;

	kvm_write_guest_cached(v->kvm, &vcpu->pv_time,
				&vcpu->hv_clock,
				sizeof(vcpu->hv_clock));
	return 0;
}
