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Commit 5a4f55cd authored by Eugene Korenevsky's avatar Eugene Korenevsky Committed by Paolo Bonzini
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KVM: x86: cache maxphyaddr CPUID leaf in struct kvm_vcpu 



cpuid_maxphyaddr(), which performs lot of memory accesses is called
extensively across KVM, especially in nVMX code.

This patch adds a cached value of maxphyaddr to vcpu.arch to reduce the
pressure onto CPU cache and simplify the code of cpuid_maxphyaddr()
callers. The cached value is initialized in kvm_arch_vcpu_init() and
reloaded every time CPUID is updated by usermode. It is obvious that
these reloads occur infrequently.

Signed-off-by: default avatarEugene Korenevsky <ekorenevsky@gmail.com>
Message-Id: <20150329205612.GA1223@gnote>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 80f0e95d

arch/x86/include/asm/kvm_host.h

+3 −1
Original line number Diff line number Diff line
@@ -426,6 +426,9 @@ struct kvm_vcpu_arch { 


	int cpuid_nent;

	struct kvm_cpuid_entry2 cpuid_entries[KVM_MAX_CPUID_ENTRIES];



	int maxphyaddr;



	/* emulate context */



	struct x86_emulate_ctxt emulate_ctxt;
@@ -1124,7 +1127,6 @@ int kvm_unmap_hva_range(struct kvm *kvm, unsigned long start, unsigned long end) 
int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end);

int kvm_test_age_hva(struct kvm *kvm, unsigned long hva);

void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte);

int cpuid_maxphyaddr(struct kvm_vcpu *vcpu);

int kvm_cpu_has_injectable_intr(struct kvm_vcpu *v);

int kvm_cpu_has_interrupt(struct kvm_vcpu *vcpu);

int kvm_arch_interrupt_allowed(struct kvm_vcpu *vcpu);

arch/x86/kvm/cpuid.c

+18 −15
Original line number Diff line number Diff line
@@ -104,6 +104,9 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu) 
		((best->eax & 0xff00) >> 8) != 0)

		return -EINVAL;



	/* Update physical-address width */

	vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);



	kvm_pmu_cpuid_update(vcpu);

	return 0;

}
@@ -135,6 +138,21 @@ static void cpuid_fix_nx_cap(struct kvm_vcpu *vcpu) 
	}

}



int cpuid_query_maxphyaddr(struct kvm_vcpu *vcpu)

{

	struct kvm_cpuid_entry2 *best;



	best = kvm_find_cpuid_entry(vcpu, 0x80000000, 0);

	if (!best || best->eax < 0x80000008)

		goto not_found;

	best = kvm_find_cpuid_entry(vcpu, 0x80000008, 0);

	if (best)

		return best->eax & 0xff;

not_found:

	return 36;

}

EXPORT_SYMBOL_GPL(cpuid_query_maxphyaddr);



/* when an old userspace process fills a new kernel module */

int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,

			     struct kvm_cpuid *cpuid,
@@ -757,21 +775,6 @@ struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu, 
}

EXPORT_SYMBOL_GPL(kvm_find_cpuid_entry);



int cpuid_maxphyaddr(struct kvm_vcpu *vcpu)

{

	struct kvm_cpuid_entry2 *best;



	best = kvm_find_cpuid_entry(vcpu, 0x80000000, 0);

	if (!best || best->eax < 0x80000008)

		goto not_found;

	best = kvm_find_cpuid_entry(vcpu, 0x80000008, 0);

	if (best)

		return best->eax & 0xff;

not_found:

	return 36;

}

EXPORT_SYMBOL_GPL(cpuid_maxphyaddr);



/*

 * If no match is found, check whether we exceed the vCPU's limit

 * and return the content of the highest valid _standard_ leaf instead.

arch/x86/kvm/cpuid.h

+6 −0
Original line number Diff line number Diff line
@@ -20,6 +20,12 @@ int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu, 
			      struct kvm_cpuid_entry2 __user *entries);

void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx);



int cpuid_query_maxphyaddr(struct kvm_vcpu *vcpu);



static inline int cpuid_maxphyaddr(struct kvm_vcpu *vcpu)

{

	return vcpu->arch.maxphyaddr;

}



static inline bool guest_cpuid_has_xsave(struct kvm_vcpu *vcpu)

{

arch/x86/kvm/x86.c

+2 −0
Original line number Diff line number Diff line
@@ -7317,6 +7317,8 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu) 
	vcpu->arch.guest_supported_xcr0 = 0;

	vcpu->arch.guest_xstate_size = XSAVE_HDR_SIZE + XSAVE_HDR_OFFSET;



	vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);



	kvm_async_pf_hash_reset(vcpu);

	kvm_pmu_init(vcpu);