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: Eugene Korenevsky <ekorenevsky@gmail.com>
Message-Id: <20150329205612.GA1223@gnote>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 8a80737..59b69f6 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -104,6 +104,9 @@
((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 @@
}
}
+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 @@
}
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.