Commit 7d6bbebb authored by David Woodhouse's avatar David Woodhouse
Browse files

KVM: x86/xen: Add kvm_xen_enabled static key 



The code paths for Xen support are all fairly lightweight but if we hide
them behind this, they're even *more* lightweight for any system which
isn't actually hosting Xen guests.

Signed-off-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
parent 78e9878c

arch/x86/kvm/x86.c

+2 −0
Original line number Diff line number Diff line
@@ -7988,6 +7988,7 @@ void kvm_arch_exit(void) 
	kvm_mmu_module_exit();

	free_percpu(user_return_msrs);

	kmem_cache_destroy(x86_fpu_cache);

	WARN_ON(static_branch_unlikely(&kvm_xen_enabled.key));

}



static int __kvm_vcpu_halt(struct kvm_vcpu *vcpu, int state, int reason)
@@ -10581,6 +10582,7 @@ void kvm_arch_destroy_vm(struct kvm *kvm) 
	kfree(srcu_dereference_check(kvm->arch.pmu_event_filter, &kvm->srcu, 1));

	kvm_mmu_uninit_vm(kvm);

	kvm_page_track_cleanup(kvm);

	kvm_xen_destroy_vm(kvm);

	kvm_hv_destroy_vm(kvm);

}

arch/x86/kvm/xen.c

+17 −0
Original line number Diff line number Diff line
@@ -16,6 +16,8 @@ 


#include "trace.h"



DEFINE_STATIC_KEY_DEFERRED_FALSE(kvm_xen_enabled, HZ);



int kvm_xen_write_hypercall_page(struct kvm_vcpu *vcpu, u64 data)

{

	struct kvm *kvm = vcpu->kvm;
@@ -93,10 +95,25 @@ int kvm_xen_hvm_config(struct kvm *kvm, struct kvm_xen_hvm_config *xhc) 
	     xhc->blob_size_32 || xhc->blob_size_64))

		return -EINVAL;



	mutex_lock(&kvm->lock);



	if (xhc->msr && !kvm->arch.xen_hvm_config.msr)

		static_branch_inc(&kvm_xen_enabled.key);

	else if (!xhc->msr && kvm->arch.xen_hvm_config.msr)

		static_branch_slow_dec_deferred(&kvm_xen_enabled);



	memcpy(&kvm->arch.xen_hvm_config, xhc, sizeof(*xhc));



	mutex_unlock(&kvm->lock);

	return 0;

}



void kvm_xen_destroy_vm(struct kvm *kvm)

{

	if (kvm->arch.xen_hvm_config.msr)

		static_branch_slow_dec_deferred(&kvm_xen_enabled);

}



static int kvm_xen_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result)

{

	kvm_rax_write(vcpu, result);

arch/x86/kvm/xen.h

+8 −2
Original line number Diff line number Diff line
@@ -9,14 +9,20 @@ 
#ifndef __ARCH_X86_KVM_XEN_H__

#define __ARCH_X86_KVM_XEN_H__



#include <linux/jump_label_ratelimit.h>



extern struct static_key_false_deferred kvm_xen_enabled;



int kvm_xen_hypercall(struct kvm_vcpu *vcpu);

int kvm_xen_write_hypercall_page(struct kvm_vcpu *vcpu, u64 data);

int kvm_xen_hvm_config(struct kvm *kvm, struct kvm_xen_hvm_config *xhc);

void kvm_xen_destroy_vm(struct kvm *kvm);



static inline bool kvm_xen_hypercall_enabled(struct kvm *kvm)

{

	return kvm->arch.xen_hvm_config.flags &

		KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL;

	return static_branch_unlikely(&kvm_xen_enabled.key) &&

		(kvm->arch.xen_hvm_config.flags &

		 KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL);

}



#endif /* __ARCH_X86_KVM_XEN_H__ */