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KVM: x86: cache maxphyaddr CPUID leaf in struct kvm_vcpu

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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: Eugene Korenevsky <ekorenevsky@gmail.com>
Message-Id: <20150329205612.GA1223@gnote>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Eugene Korenevsky 2015-03-29 23:56:12 +03:00 committed by Paolo Bonzini
parent 80f0e95d1b
commit 5a4f55cde8
4 changed files with 29 additions and 16 deletions
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4
arch/x86/include/asm/kvm_host.h
View File

@ -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);

33
arch/x86/kvm/cpuid.c
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@ -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.

6
arch/x86/kvm/cpuid.h
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@ -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)
{

2
arch/x86/kvm/x86.c
View File

@ -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);