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Date: Thu, 1 Oct 2020 14:29:54 +0300
From: Maxim Levitsky <mlevitsk@...hat.com>
To: kvm@...r.kernel.org
Cc: Borislav Petkov <bp@...en8.de>,
x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Sean Christopherson <sean.j.christopherson@...el.com>,
Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Joerg Roedel <joro@...tes.org>,
Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH v7 4/4] 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: Maxim Levitsky <mlevitsk@...hat.com>
---
arch/x86/kvm/svm/nested.c | 42 +++++++++++++++++++++++++++
arch/x86/kvm/svm/svm.c | 61 +++++++++++++++++++++------------------
arch/x86/kvm/svm/svm.h | 8 +++++
3 files changed, 83 insertions(+), 28 deletions(-)
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index ba50ff6e35c7c..9e4c226dbf7d9 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -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.
*/
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 57e0f27ff7d20..dc4fe579d460e 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -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);
}
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index e7af21e6fe1e0..1d853fe4c778b 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -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);
--
2.26.2
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