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kvm: x86: Dynamically allocate guest_fpu

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Previously, the guest_fpu field was embedded in the kvm_vcpu_arch
struct. Unfortunately, the field is quite large, (e.g., 4352 bytes on my
current setup). This bloats the kvm_vcpu_arch struct for x86 into an
order 3 memory allocation, which can become a problem on overcommitted
machines. Thus, this patch moves the fpu state outside of the
kvm_vcpu_arch struct.

With this patch applied, the kvm_vcpu_arch struct is reduced to 15168
bytes for vmx on my setup when building the kernel with kvmconfig.

Suggested-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Marc Orr <marcorr@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Marc Orr
2018-11-06 14:53:56 -08:00
committed by Paolo Bonzini
parent 240c35a378
commit b666a4b697
4 changed files with 60 additions and 14 deletions
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3
arch/x86/include/asm/kvm_host.h
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@@ -610,7 +610,7 @@ struct kvm_vcpu_arch {
* "guest_fpu" state here contains the guest FPU context, with the
* host PRKU bits.
*/
struct fpu guest_fpu;
struct fpu *guest_fpu;
u64 xcr0;
u64 guest_supported_xcr0;
@@ -1196,6 +1196,7 @@ struct kvm_arch_async_pf {
};
extern struct kvm_x86_ops *kvm_x86_ops;
extern struct kmem_cache *x86_fpu_cache;
#define __KVM_HAVE_ARCH_VM_ALLOC
static inline struct kvm *kvm_arch_alloc_vm(void)