Commit 28d1629f authored by David Woodhouse's avatar David Woodhouse Committed by Paolo Bonzini
Browse files

KVM: x86/xen: Kernel acceleration for XENVER_version 



Turns out this is a fast path for PV guests because they use it to
trigger the event channel upcall. So letting it bounce all the way up
to userspace is not great.

Signed-off-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220303154127.202856-14-dwmw2@infradead.org>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 53639526

arch/x86/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -1026,6 +1026,7 @@ struct msr_bitmap_range { 


/* Xen emulation context */

struct kvm_xen {

	u32 xen_version;

	bool long_mode;

	u8 upcall_vector;

	struct gfn_to_pfn_cache shinfo_cache;

arch/x86/kvm/xen.c

+19 −0
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
#include <trace/events/kvm.h>

#include <xen/interface/xen.h>

#include <xen/interface/vcpu.h>

#include <xen/interface/version.h>

#include <xen/interface/event_channel.h>

#include <xen/interface/sched.h>
@@ -465,6 +466,13 @@ int kvm_xen_hvm_set_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data) 
		r = kvm_xen_setattr_evtchn(kvm, data);

		break;



	case KVM_XEN_ATTR_TYPE_XEN_VERSION:

		mutex_lock(&kvm->lock);

		kvm->arch.xen.xen_version = data->u.xen_version;

		mutex_unlock(&kvm->lock);

		r = 0;

		break;



	default:

		break;

	}
@@ -497,6 +505,11 @@ int kvm_xen_hvm_get_attr(struct kvm *kvm, struct kvm_xen_hvm_attr *data) 
		r = 0;

		break;



	case KVM_XEN_ATTR_TYPE_XEN_VERSION:

		data->u.xen_version = kvm->arch.xen.xen_version;

		r = 0;

		break;



	default:

		break;

	}
@@ -1059,6 +1072,12 @@ int kvm_xen_hypercall(struct kvm_vcpu *vcpu) 
				params[3], params[4], params[5]);



	switch (input) {

	case __HYPERVISOR_xen_version:

		if (params[0] == XENVER_version && vcpu->kvm->arch.xen.xen_version) {

			r = vcpu->kvm->arch.xen.xen_version;

			handled = true;

		}

		break;

	case __HYPERVISOR_event_channel_op:

		if (params[0] == EVTCHNOP_send)

			handled = kvm_xen_hcall_evtchn_send(vcpu, params[1], &r);

include/uapi/linux/kvm.h

+2 −1
Original line number Diff line number Diff line
@@ -1711,7 +1711,7 @@ struct kvm_xen_hvm_attr { 
				__u32 padding[4];

			} deliver;

		} evtchn;



		__u32 xen_version;

		__u64 pad[8];

	} u;

};
@@ -1722,6 +1722,7 @@ struct kvm_xen_hvm_attr { 
#define KVM_XEN_ATTR_TYPE_UPCALL_VECTOR		0x2

/* Available with KVM_CAP_XEN_HVM / KVM_XEN_HVM_CONFIG_EVTCHN_SEND */

#define KVM_XEN_ATTR_TYPE_EVTCHN		0x3

#define KVM_XEN_ATTR_TYPE_XEN_VERSION		0x4



/* Per-vCPU Xen attributes */

#define KVM_XEN_VCPU_GET_ATTR	_IOWR(KVMIO, 0xca, struct kvm_xen_vcpu_attr)