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Commit b666a4b6 authored by Marc Orr's avatar Marc Orr Committed by Paolo Bonzini
Browse files

kvm: x86: Dynamically allocate guest_fpu 



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: default avatarDave Hansen <dave.hansen@intel.com>
Signed-off-by: default avatarMarc Orr <marcorr@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 240c35a3

arch/x86/include/asm/kvm_host.h

+2 −1
Original line number Diff line number Diff line
@@ -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)

arch/x86/kvm/svm.c

+10 −0
Original line number Diff line number Diff line
@@ -2125,6 +2125,13 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id) 
		goto out;

	}



	svm->vcpu.arch.guest_fpu = kmem_cache_zalloc(x86_fpu_cache, GFP_KERNEL);

	if (!svm->vcpu.arch.guest_fpu) {

		printk(KERN_ERR "kvm: failed to allocate vcpu's fpu\n");

		err = -ENOMEM;

		goto free_partial_svm;

	}



	err = kvm_vcpu_init(&svm->vcpu, kvm, id);

	if (err)

		goto free_svm;
@@ -2184,6 +2191,8 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id) 
uninit:

	kvm_vcpu_uninit(&svm->vcpu);

free_svm:

	kmem_cache_free(x86_fpu_cache, svm->vcpu.arch.guest_fpu);

free_partial_svm:

	kmem_cache_free(kvm_vcpu_cache, svm);

out:

	return ERR_PTR(err);
@@ -2213,6 +2222,7 @@ static void svm_free_vcpu(struct kvm_vcpu *vcpu) 
	__free_page(virt_to_page(svm->nested.hsave));

	__free_pages(virt_to_page(svm->nested.msrpm), MSRPM_ALLOC_ORDER);

	kvm_vcpu_uninit(vcpu);

	kmem_cache_free(x86_fpu_cache, svm->vcpu.arch.guest_fpu);

	kmem_cache_free(kvm_vcpu_cache, svm);

}

arch/x86/kvm/vmx/vmx.c

+10 −0
Original line number Diff line number Diff line
@@ -6349,6 +6349,7 @@ static void vmx_free_vcpu(struct kvm_vcpu *vcpu) 
	free_loaded_vmcs(vmx->loaded_vmcs);

	kfree(vmx->guest_msrs);

	kvm_vcpu_uninit(vcpu);

	kmem_cache_free(x86_fpu_cache, vmx->vcpu.arch.guest_fpu);

	kmem_cache_free(kvm_vcpu_cache, vmx);

}
@@ -6362,6 +6363,13 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id) 
	if (!vmx)

		return ERR_PTR(-ENOMEM);



	vmx->vcpu.arch.guest_fpu = kmem_cache_zalloc(x86_fpu_cache, GFP_KERNEL);

	if (!vmx->vcpu.arch.guest_fpu) {

		printk(KERN_ERR "kvm: failed to allocate vcpu's fpu\n");

		err = -ENOMEM;

		goto free_partial_vcpu;

	}



	vmx->vpid = allocate_vpid();



	err = kvm_vcpu_init(&vmx->vcpu, kvm, id);
@@ -6454,6 +6462,8 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id) 
	kvm_vcpu_uninit(&vmx->vcpu);

free_vcpu:

	free_vpid(vmx->vpid);

	kmem_cache_free(x86_fpu_cache, vmx->vcpu.arch.guest_fpu);

free_partial_vcpu:

	kmem_cache_free(kvm_vcpu_cache, vmx);

	return ERR_PTR(err);

}

arch/x86/kvm/x86.c

+38 −13
Original line number Diff line number Diff line
@@ -213,6 +213,9 @@ struct kvm_stats_debugfs_item debugfs_entries[] = { 


u64 __read_mostly host_xcr0;



struct kmem_cache *x86_fpu_cache;

EXPORT_SYMBOL_GPL(x86_fpu_cache);



static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt);



static inline void kvm_async_pf_hash_reset(struct kvm_vcpu *vcpu)
@@ -3630,7 +3633,7 @@ static int kvm_vcpu_ioctl_x86_set_debugregs(struct kvm_vcpu *vcpu, 


static void fill_xsave(u8 *dest, struct kvm_vcpu *vcpu)

{

	struct xregs_state *xsave = &vcpu->arch.guest_fpu.state.xsave;

	struct xregs_state *xsave = &vcpu->arch.guest_fpu->state.xsave;

	u64 xstate_bv = xsave->header.xfeatures;

	u64 valid;
@@ -3672,7 +3675,7 @@ static void fill_xsave(u8 *dest, struct kvm_vcpu *vcpu) 


static void load_xsave(struct kvm_vcpu *vcpu, u8 *src)

{

	struct xregs_state *xsave = &vcpu->arch.guest_fpu.state.xsave;

	struct xregs_state *xsave = &vcpu->arch.guest_fpu->state.xsave;

	u64 xstate_bv = *(u64 *)(src + XSAVE_HDR_OFFSET);

	u64 valid;
@@ -3720,7 +3723,7 @@ static void kvm_vcpu_ioctl_x86_get_xsave(struct kvm_vcpu *vcpu, 
		fill_xsave((u8 *) guest_xsave->region, vcpu);

	} else {

		memcpy(guest_xsave->region,

			&vcpu->arch.guest_fpu.state.fxsave,

			&vcpu->arch.guest_fpu->state.fxsave,

			sizeof(struct fxregs_state));

		*(u64 *)&guest_xsave->region[XSAVE_HDR_OFFSET / sizeof(u32)] =

			XFEATURE_MASK_FPSSE;
@@ -3750,7 +3753,7 @@ static int kvm_vcpu_ioctl_x86_set_xsave(struct kvm_vcpu *vcpu, 
		if (xstate_bv & ~XFEATURE_MASK_FPSSE ||

			mxcsr & ~mxcsr_feature_mask)

			return -EINVAL;

		memcpy(&vcpu->arch.guest_fpu.state.fxsave,

		memcpy(&vcpu->arch.guest_fpu->state.fxsave,

			guest_xsave->region, sizeof(struct fxregs_state));

	}

	return 0;
@@ -6852,11 +6855,30 @@ int kvm_arch_init(void *opaque) 
		goto out;

	}



	/*

	 * KVM explicitly assumes that the guest has an FPU and

	 * FXSAVE/FXRSTOR. For example, the KVM_GET_FPU explicitly casts the

	 * vCPU's FPU state as a fxregs_state struct.

	 */

	if (!boot_cpu_has(X86_FEATURE_FPU) || !boot_cpu_has(X86_FEATURE_FXSR)) {

		printk(KERN_ERR "kvm: inadequate fpu\n");

		r = -EOPNOTSUPP;

		goto out;

	}



	r = -ENOMEM;

	x86_fpu_cache = kmem_cache_create("x86_fpu", fpu_kernel_xstate_size,

					  __alignof__(struct fpu), SLAB_ACCOUNT,

					  NULL);

	if (!x86_fpu_cache) {

		printk(KERN_ERR "kvm: failed to allocate cache for x86 fpu\n");

		goto out;

	}



	shared_msrs = alloc_percpu(struct kvm_shared_msrs);

	if (!shared_msrs) {

		printk(KERN_ERR "kvm: failed to allocate percpu kvm_shared_msrs\n");

		goto out;

		goto out_free_x86_fpu_cache;

	}



	r = kvm_mmu_module_init();
@@ -6889,6 +6911,8 @@ int kvm_arch_init(void *opaque) 


out_free_percpu:

	free_percpu(shared_msrs);

out_free_x86_fpu_cache:

	kmem_cache_destroy(x86_fpu_cache);

out:

	return r;

}
@@ -6912,6 +6936,7 @@ void kvm_arch_exit(void) 
	kvm_x86_ops = NULL;

	kvm_mmu_module_exit();

	free_percpu(shared_msrs);

	kmem_cache_destroy(x86_fpu_cache);

}



int kvm_vcpu_halt(struct kvm_vcpu *vcpu)
@@ -8037,7 +8062,7 @@ static void kvm_load_guest_fpu(struct kvm_vcpu *vcpu) 
	preempt_disable();

	copy_fpregs_to_fpstate(&current->thread.fpu);

	/* PKRU is separately restored in kvm_x86_ops->run.  */

	__copy_kernel_to_fpregs(&vcpu->arch.guest_fpu.state,

	__copy_kernel_to_fpregs(&vcpu->arch.guest_fpu->state,

				~XFEATURE_MASK_PKRU);

	preempt_enable();

	trace_kvm_fpu(1);
@@ -8047,7 +8072,7 @@ static void kvm_load_guest_fpu(struct kvm_vcpu *vcpu) 
static void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)

{

	preempt_disable();

	copy_fpregs_to_fpstate(&vcpu->arch.guest_fpu);

	copy_fpregs_to_fpstate(vcpu->arch.guest_fpu);

	copy_kernel_to_fpregs(&current->thread.fpu.state);

	preempt_enable();

	++vcpu->stat.fpu_reload;
@@ -8542,7 +8567,7 @@ int kvm_arch_vcpu_ioctl_get_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu) 


	vcpu_load(vcpu);



	fxsave = &vcpu->arch.guest_fpu.state.fxsave;

	fxsave = &vcpu->arch.guest_fpu->state.fxsave;

	memcpy(fpu->fpr, fxsave->st_space, 128);

	fpu->fcw = fxsave->cwd;

	fpu->fsw = fxsave->swd;
@@ -8562,7 +8587,7 @@ int kvm_arch_vcpu_ioctl_set_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu) 


	vcpu_load(vcpu);



	fxsave = &vcpu->arch.guest_fpu.state.fxsave;

	fxsave = &vcpu->arch.guest_fpu->state.fxsave;



	memcpy(fxsave->st_space, fpu->fpr, 128);

	fxsave->cwd = fpu->fcw;
@@ -8618,9 +8643,9 @@ static int sync_regs(struct kvm_vcpu *vcpu) 


static void fx_init(struct kvm_vcpu *vcpu)

{

	fpstate_init(&vcpu->arch.guest_fpu.state);

	fpstate_init(&vcpu->arch.guest_fpu->state);

	if (boot_cpu_has(X86_FEATURE_XSAVES))

		vcpu->arch.guest_fpu.state.xsave.header.xcomp_bv =

		vcpu->arch.guest_fpu->state.xsave.header.xcomp_bv =

			host_xcr0 | XSTATE_COMPACTION_ENABLED;



	/*
@@ -8745,11 +8770,11 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) 
		 */

		if (init_event)

			kvm_put_guest_fpu(vcpu);

		mpx_state_buffer = get_xsave_addr(&vcpu->arch.guest_fpu.state.xsave,

		mpx_state_buffer = get_xsave_addr(&vcpu->arch.guest_fpu->state.xsave,

					XFEATURE_MASK_BNDREGS);

		if (mpx_state_buffer)

			memset(mpx_state_buffer, 0, sizeof(struct mpx_bndreg_state));

		mpx_state_buffer = get_xsave_addr(&vcpu->arch.guest_fpu.state.xsave,

		mpx_state_buffer = get_xsave_addr(&vcpu->arch.guest_fpu->state.xsave,

					XFEATURE_MASK_BNDCSR);

		if (mpx_state_buffer)

			memset(mpx_state_buffer, 0, sizeof(struct mpx_bndcsr));