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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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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.