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

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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: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20201001112954.6258-5-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Maxim Levitsky 2020-10-01 14:29:54 +03:00 committed by Paolo Bonzini
parent 72f211ecaa
commit 2fcf4876ad
3 changed files with 83 additions and 28 deletions
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42
arch/x86/kvm/svm/nested.c
View File

@ -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.
*/

61
arch/x86/kvm/svm/svm.c
View File

@ -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 (!(efer & EFER_SVME)) {
svm_leave_nested(svm);
svm_set_gif(svm, true);
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);
}

8
arch/x86/kvm/svm/svm.h
View File

@ -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);