Commit d9a710e5 authored by Wanpeng Li's avatar Wanpeng Li Committed by Paolo Bonzini
Browse files

KVM: X86: Dynamically allocate user_fpu 



After reverting commit 240c35a3 (kvm: x86: Use task structs fpu field
for user), struct kvm_vcpu is 19456 bytes on my server, PAGE_ALLOC_COSTLY_ORDER(3)
is the order at which allocations are deemed costly to service. In serveless
scenario, one host can service hundreds/thoudands firecracker/kata-container
instances, howerver, new instance will fail to launch after memory is too
fragmented to allocate kvm_vcpu struct on host, this was observed in some
cloud provider product environments.

This patch dynamically allocates user_fpu, kvm_vcpu is 15168 bytes now on my
Skylake server.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: default avatarWanpeng Li <wanpengli@tencent.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent e7517324

arch/x86/include/asm/kvm_host.h

+1 −1
Original line number Diff line number Diff line
@@ -616,7 +616,7 @@ struct kvm_vcpu_arch { 
	 * "guest_fpu" state here contains the guest FPU context, with the

	 * host PRKU bits.

	 */

	struct fpu user_fpu;

	struct fpu *user_fpu;

	struct fpu *guest_fpu;



	u64 xcr0;

arch/x86/kvm/svm.c

+12 −1
Original line number Diff line number Diff line
@@ -2143,12 +2143,20 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id) 
		goto out;

	}



	svm->vcpu.arch.user_fpu = kmem_cache_zalloc(x86_fpu_cache,

						     GFP_KERNEL_ACCOUNT);

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

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

		err = -ENOMEM;

		goto free_partial_svm;

	}



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

						     GFP_KERNEL_ACCOUNT);

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

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

		err = -ENOMEM;

		goto free_partial_svm;

		goto free_user_fpu;

	}



	err = kvm_vcpu_init(&svm->vcpu, kvm, id);
@@ -2211,6 +2219,8 @@ uninit: 
	kvm_vcpu_uninit(&svm->vcpu);

free_svm:

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

free_user_fpu:

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

free_partial_svm:

	kmem_cache_free(kvm_vcpu_cache, svm);

out:
@@ -2241,6 +2251,7 @@ 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.user_fpu);

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

	kmem_cache_free(kvm_vcpu_cache, svm);

}

arch/x86/kvm/vmx/vmx.c

+12 −1
Original line number Diff line number Diff line
@@ -6598,6 +6598,7 @@ 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.user_fpu);

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

	kmem_cache_free(kvm_vcpu_cache, vmx);

}
@@ -6613,12 +6614,20 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id) 
	if (!vmx)

		return ERR_PTR(-ENOMEM);



	vmx->vcpu.arch.user_fpu = kmem_cache_zalloc(x86_fpu_cache,

			GFP_KERNEL_ACCOUNT);

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

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

		err = -ENOMEM;

		goto free_partial_vcpu;

	}



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

			GFP_KERNEL_ACCOUNT);

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

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

		err = -ENOMEM;

		goto free_partial_vcpu;

		goto free_user_fpu;

	}



	vmx->vpid = allocate_vpid();
@@ -6721,6 +6730,8 @@ uninit_vcpu: 
free_vcpu:

	free_vpid(vmx->vpid);

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

free_user_fpu:

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

free_partial_vcpu:

	kmem_cache_free(kvm_vcpu_cache, vmx);

	return ERR_PTR(err);

arch/x86/kvm/x86.c

+2 −2
Original line number Diff line number Diff line
@@ -8273,7 +8273,7 @@ static void kvm_load_guest_fpu(struct kvm_vcpu *vcpu) 
{

	fpregs_lock();



	copy_fpregs_to_fpstate(&vcpu->arch.user_fpu);

	copy_fpregs_to_fpstate(vcpu->arch.user_fpu);

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

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

				~XFEATURE_MASK_PKRU);
@@ -8290,7 +8290,7 @@ static void kvm_put_guest_fpu(struct kvm_vcpu *vcpu) 
	fpregs_lock();



	copy_fpregs_to_fpstate(vcpu->arch.guest_fpu);

	copy_kernel_to_fpregs(&vcpu->arch.user_fpu.state);

	copy_kernel_to_fpregs(&vcpu->arch.user_fpu->state);



	fpregs_mark_activate();

	fpregs_unlock();

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