Commit fde0451b authored by David Woodhouse's avatar David Woodhouse Committed by Paolo Bonzini
Browse files

KVM: x86/xen: Support per-vCPU event channel upcall via local APIC 



Windows uses a per-vCPU vector, and it's delivered via the local APIC
basically like an MSI (with associated EOI) unlike the traditional
guest-wide vector which is just magically asserted by Xen (and in the
KVM case by kvm_xen_has_interrupt() / kvm_cpu_get_extint()).

Now that the kernel is able to raise event channel events for itself,
being able to do so for Windows guests is also going to be useful.

Signed-off-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220303154127.202856-15-dwmw2@infradead.org>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 28d1629f

arch/x86/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -606,6 +606,7 @@ struct kvm_vcpu_hv { 
struct kvm_vcpu_xen {

	u64 hypercall_rip;

	u32 current_runstate;

	u8 upcall_vector;

	struct gfn_to_pfn_cache vcpu_info_cache;

	struct gfn_to_pfn_cache vcpu_time_info_cache;

	struct gfn_to_pfn_cache runstate_cache;

arch/x86/kvm/xen.c

+40 −0
Original line number Diff line number Diff line
@@ -314,6 +314,22 @@ void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, int state) 
	mark_page_dirty_in_slot(v->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);

}



static void kvm_xen_inject_vcpu_vector(struct kvm_vcpu *v)

{

	struct kvm_lapic_irq irq = { };

	int r;



	irq.dest_id = v->vcpu_id;

	irq.vector = v->arch.xen.upcall_vector;

	irq.dest_mode = APIC_DEST_PHYSICAL;

	irq.shorthand = APIC_DEST_NOSHORT;

	irq.delivery_mode = APIC_DM_FIXED;

	irq.level = 1;



	/* The fast version will always work for physical unicast */

	WARN_ON_ONCE(!kvm_irq_delivery_to_apic_fast(v->kvm, NULL, &irq, &r, NULL));

}



/*

 * On event channel delivery, the vcpu_info may not have been accessible.

 * In that case, there are bits in vcpu->arch.xen.evtchn_pending_sel which
@@ -374,6 +390,10 @@ void kvm_xen_inject_pending_events(struct kvm_vcpu *v) 
	}

	read_unlock_irqrestore(&gpc->lock, flags);



	/* For the per-vCPU lapic vector, deliver it as MSI. */

	if (v->arch.xen.upcall_vector)

		kvm_xen_inject_vcpu_vector(v);



	mark_page_dirty_in_slot(v->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT);

}
@@ -708,6 +728,15 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data) 
		r = 0;

		break;



	case KVM_XEN_VCPU_ATTR_TYPE_UPCALL_VECTOR:

		if (data->u.vector && data->u.vector < 0x10)

			r = -EINVAL;

		else {

			vcpu->arch.xen.upcall_vector = data->u.vector;

			r = 0;

		}

		break;



	default:

		break;

	}
@@ -795,6 +824,11 @@ int kvm_xen_vcpu_get_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data) 
		r = 0;

		break;



	case KVM_XEN_VCPU_ATTR_TYPE_UPCALL_VECTOR:

		data->u.vector = vcpu->arch.xen.upcall_vector;

		r = 0;

		break;



	default:

		break;

	}
@@ -1228,6 +1262,12 @@ int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe, struct kvm *kvm) 
				kick_vcpu = true;

			}

		}



		/* For the per-vCPU lapic vector, deliver it as MSI. */

		if (kick_vcpu && vcpu->arch.xen.upcall_vector) {

			kvm_xen_inject_vcpu_vector(vcpu);

			kick_vcpu = false;

		}

	}



 out_rcu:

include/uapi/linux/kvm.h

+2 −0
Original line number Diff line number Diff line
@@ -1754,6 +1754,7 @@ struct kvm_xen_vcpu_attr { 
			__u32 priority;

			__u64 expires_ns;

		} timer;

		__u8 vector;

	} u;

};
@@ -1767,6 +1768,7 @@ struct kvm_xen_vcpu_attr { 
/* Available with KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_EVTCHN_SEND */

#define KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID		0x6

#define KVM_XEN_VCPU_ATTR_TYPE_TIMER		0x7

#define KVM_XEN_VCPU_ATTR_TYPE_UPCALL_VECTOR	0x8



/* Secure Encrypted Virtualization command */

enum sev_cmd_id {