Commit 2fcf4876 authored by Maxim Levitsky's avatar Maxim Levitsky Committed by Paolo Bonzini
Browse files

KVM: nSVM: implement on demand allocation of the nested state 



This way we don't waste memory on VMs which don't use nesting
virtualization even when the host enabled it for them.

Signed-off-by: default avatarMaxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20201001112954.6258-5-mlevitsk@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 72f211ec

arch/x86/kvm/svm/nested.c

+42 −0
Original line number Diff line number Diff line
@@ -481,6 +481,9 @@ int nested_svm_vmrun(struct vcpu_svm *svm) 


	vmcb12 = map.hva;



	if (WARN_ON_ONCE(!svm->nested.initialized))

		return -EINVAL;



	if (!nested_vmcb_checks(svm, vmcb12)) {

		vmcb12->control.exit_code    = SVM_EXIT_ERR;

		vmcb12->control.exit_code_hi = 0;
@@ -698,6 +701,45 @@ int nested_svm_vmexit(struct vcpu_svm *svm) 
	return 0;

}



int svm_allocate_nested(struct vcpu_svm *svm)

{

	struct page *hsave_page;



	if (svm->nested.initialized)

		return 0;



	hsave_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);

	if (!hsave_page)

		return -ENOMEM;

	svm->nested.hsave = page_address(hsave_page);



	svm->nested.msrpm = svm_vcpu_alloc_msrpm();

	if (!svm->nested.msrpm)

		goto err_free_hsave;

	svm_vcpu_init_msrpm(&svm->vcpu, svm->nested.msrpm);



	svm->nested.initialized = true;

	return 0;



err_free_hsave:

	__free_page(hsave_page);

	return -ENOMEM;

}



void svm_free_nested(struct vcpu_svm *svm)

{

	if (!svm->nested.initialized)

		return;



	svm_vcpu_free_msrpm(svm->nested.msrpm);

	svm->nested.msrpm = NULL;



	__free_page(virt_to_page(svm->nested.hsave));

	svm->nested.hsave = NULL;



	svm->nested.initialized = false;

}



/*

 * Forcibly leave nested mode in order to be able to reset the VCPU later on.

 */

arch/x86/kvm/svm/svm.c

+33 −28
Original line number Diff line number Diff line
@@ -266,6 +266,7 @@ static int get_max_npt_level(void) 
int svm_set_efer(struct kvm_vcpu *vcpu, u64 efer)

{

	struct vcpu_svm *svm = to_svm(vcpu);

	u64 old_efer = vcpu->arch.efer;

	vcpu->arch.efer = efer;



	if (!npt_enabled) {
@@ -276,9 +277,27 @@ int svm_set_efer(struct kvm_vcpu *vcpu, u64 efer) 
			efer &= ~EFER_LME;

	}



	if ((old_efer & EFER_SVME) != (efer & EFER_SVME)) {

		if (!(efer & EFER_SVME)) {

			svm_leave_nested(svm);

			svm_set_gif(svm, true);



			/*

			 * Free the nested guest state, unless we are in SMM.

			 * In this case we will return to the nested guest

			 * as soon as we leave SMM.

			 */

			if (!is_smm(&svm->vcpu))

				svm_free_nested(svm);



		} else {

			int ret = svm_allocate_nested(svm);



			if (ret) {

				vcpu->arch.efer = old_efer;

				return ret;

			}

		}

	}



	svm->vmcb->save.efer = efer | EFER_SVME;
@@ -650,7 +669,7 @@ static void set_msr_interception(struct kvm_vcpu *vcpu, u32 *msrpm, u32 msr, 
	set_msr_interception_bitmap(vcpu, msrpm, msr, read, write);

}



static u32 *svm_vcpu_alloc_msrpm(void)

u32 *svm_vcpu_alloc_msrpm(void)

{

	struct page *pages = alloc_pages(GFP_KERNEL_ACCOUNT, MSRPM_ALLOC_ORDER);

	u32 *msrpm;
@@ -664,7 +683,7 @@ static u32 *svm_vcpu_alloc_msrpm(void) 
	return msrpm;

}



static void svm_vcpu_init_msrpm(struct kvm_vcpu *vcpu, u32 *msrpm)

void svm_vcpu_init_msrpm(struct kvm_vcpu *vcpu, u32 *msrpm)

{

	int i;
@@ -675,7 +694,8 @@ static void svm_vcpu_init_msrpm(struct kvm_vcpu *vcpu, u32 *msrpm) 
	}

}



static void svm_vcpu_free_msrpm(u32 *msrpm)



void svm_vcpu_free_msrpm(u32 *msrpm)

{

	__free_pages(virt_to_page(msrpm), MSRPM_ALLOC_ORDER);

}
@@ -1268,7 +1288,6 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu) 
{

	struct vcpu_svm *svm;

	struct page *vmcb_page;

	struct page *hsave_page;

	int err;



	BUILD_BUG_ON(offsetof(struct vcpu_svm, vcpu) != 0);
@@ -1279,13 +1298,9 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu) 
	if (!vmcb_page)

		goto out;



	hsave_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);

	if (!hsave_page)

		goto error_free_vmcb_page;



	err = avic_init_vcpu(svm);

	if (err)

		goto error_free_hsave_page;

		goto error_free_vmcb_page;



	/* We initialize this flag to true to make sure that the is_running

	 * bit would be set the first time the vcpu is loaded.
@@ -1293,21 +1308,12 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu) 
	if (irqchip_in_kernel(vcpu->kvm) && kvm_apicv_activated(vcpu->kvm))

		svm->avic_is_running = true;



	svm->nested.hsave = page_address(hsave_page);



	svm->msrpm = svm_vcpu_alloc_msrpm();

	if (!svm->msrpm)

		goto error_free_hsave_page;

		goto error_free_vmcb_page;



	svm_vcpu_init_msrpm(vcpu, svm->msrpm);



	svm->nested.msrpm = svm_vcpu_alloc_msrpm();

	if (!svm->nested.msrpm)

		goto error_free_msrpm;



	/* We only need the L1 pass-through MSR state, so leave vcpu as NULL */

	svm_vcpu_init_msrpm(vcpu, svm->nested.msrpm);



	svm->vmcb = page_address(vmcb_page);

	svm->vmcb_pa = __sme_set(page_to_pfn(vmcb_page) << PAGE_SHIFT);

	svm->asid_generation = 0;
@@ -1318,10 +1324,6 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu) 


	return 0;



error_free_msrpm:

	svm_vcpu_free_msrpm(svm->msrpm);

error_free_hsave_page:

	__free_page(hsave_page);

error_free_vmcb_page:

	__free_page(vmcb_page);

out:
@@ -1347,10 +1349,10 @@ static void svm_free_vcpu(struct kvm_vcpu *vcpu) 
	 */

	svm_clear_current_vmcb(svm->vmcb);



	svm_free_nested(svm);



	__free_page(pfn_to_page(__sme_clr(svm->vmcb_pa) >> PAGE_SHIFT));

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

	__free_page(virt_to_page(svm->nested.hsave));

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

}



static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
@@ -4038,6 +4040,9 @@ static int svm_pre_leave_smm(struct kvm_vcpu *vcpu, const char *smstate) 
					 gpa_to_gfn(vmcb12_gpa), &map) == -EINVAL)

				return 1;



			if (svm_allocate_nested(svm))

				return 1;



			ret = enter_svm_guest_mode(svm, vmcb12_gpa, map.hva);

			kvm_vcpu_unmap(&svm->vcpu, &map, true);

		}

arch/x86/kvm/svm/svm.h

+8 −0
Original line number Diff line number Diff line
@@ -97,6 +97,8 @@ struct svm_nested_state { 


	/* cache for control fields of the guest */

	struct vmcb_control_area ctl;



	bool initialized;

};



struct vcpu_svm {
@@ -350,6 +352,10 @@ static inline bool gif_set(struct vcpu_svm *svm) 
#define MSR_INVALID				0xffffffffU



u32 svm_msrpm_offset(u32 msr);

u32 *svm_vcpu_alloc_msrpm(void);

void svm_vcpu_init_msrpm(struct kvm_vcpu *vcpu, u32 *msrpm);

void svm_vcpu_free_msrpm(u32 *msrpm);



int svm_set_efer(struct kvm_vcpu *vcpu, u64 efer);

void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0);

int svm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
@@ -391,6 +397,8 @@ static inline bool nested_exit_on_nmi(struct vcpu_svm *svm) 
int enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,

			 struct vmcb *nested_vmcb);

void svm_leave_nested(struct vcpu_svm *svm);

void svm_free_nested(struct vcpu_svm *svm);

int svm_allocate_nested(struct vcpu_svm *svm);

int nested_svm_vmrun(struct vcpu_svm *svm);

void nested_svm_vmloadsave(struct vmcb *from_vmcb, struct vmcb *to_vmcb);

int nested_svm_vmexit(struct vcpu_svm *svm);