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Date: Thu, 27 Aug 2020 20:04:34 +0300
From: Maxim Levitsky <mlevitsk@...hat.com>
To: kvm@...r.kernel.org
Cc: Joerg Roedel <joro@...tes.org>, Borislav Petkov <bp@...en8.de>,
Paolo Bonzini <pbonzini@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
Ingo Molnar <mingo@...hat.com>,
x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
Vitaly Kuznetsov <vkuznets@...hat.com>,
Jim Mattson <jmattson@...gle.com>,
Wanpeng Li <wanpengli@...cent.com>,
Thomas Gleixner <tglx@...utronix.de>,
Sean Christopherson <sean.j.christopherson@...el.com>,
Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 8/8] KVM: nSVM: implement ondemand allocation of the nested state
This way we don't waste memory on VMs which don't use
nesting virtualization even if it is available to them.
Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
---
arch/x86/kvm/svm/nested.c | 42 +++++++++++++++++++++++++++++++
arch/x86/kvm/svm/svm.c | 52 +++++++++++++++++++++------------------
arch/x86/kvm/svm/svm.h | 6 +++++
3 files changed, 76 insertions(+), 24 deletions(-)
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 7b1c98826c365..e2f8e94e6b83c 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -471,6 +471,9 @@ int nested_svm_vmrun(struct vcpu_svm *svm)
vmcb12 = map.hva;
+ if (WARN_ON(!svm->nested.initialized))
+ return 1;
+
if (!nested_vmcb_checks(svm, vmcb12)) {
vmcb12->control.exit_code = SVM_EXIT_ERR;
vmcb12->control.exit_code_hi = 0;
@@ -686,6 +689,45 @@ 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)
+ goto error;
+
+ svm->nested.hsave = page_address(hsave_page);
+
+ svm->nested.msrpm = svm_vcpu_init_msrpm();
+ if (!svm->nested.msrpm)
+ goto err_free_hsave;
+
+ svm->nested.initialized = true;
+ return 0;
+err_free_hsave:
+ __free_page(hsave_page);
+error:
+ return 1;
+}
+
+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 4c92432e33e27..7ab142ed9c5c0 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) {
@@ -276,14 +277,31 @@ 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 state unless we are in SMM, in which
+ * case the exit from SVM mode is only for duration of the SMI
+ * handler
+ */
+ if (!is_smm(&svm->vcpu))
+ svm_free_nested(svm);
+
+ } else {
+ if (svm_allocate_nested(svm))
+ goto error;
+ }
}
svm->vmcb->save.efer = efer | EFER_SVME;
vmcb_mark_dirty(svm->vmcb, VMCB_CR);
return 0;
+error:
+ vcpu->arch.efer = old_efer;
+ return 1;
}
static int is_external_interrupt(u32 info)
@@ -610,7 +628,7 @@ static void set_msr_interception(u32 *msrpm, unsigned msr,
msrpm[offset] = tmp;
}
-static u32 *svm_vcpu_init_msrpm(void)
+u32 *svm_vcpu_init_msrpm(void)
{
int i;
u32 *msrpm;
@@ -630,7 +648,7 @@ static u32 *svm_vcpu_init_msrpm(void)
return 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);
}
@@ -1184,7 +1202,6 @@ 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);
@@ -1195,13 +1212,9 @@ 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 out;
/* We initialize this flag to true to make sure that the is_running
* bit would be set the first time the vcpu is loaded.
@@ -1209,15 +1222,9 @@ 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_init_msrpm();
if (!svm->msrpm)
- goto error_free_hsave_page;
-
- svm->nested.msrpm = svm_vcpu_init_msrpm();
- if (!svm->nested.msrpm)
- goto error_free_msrpm;
+ goto error_free_vmcb_page;
svm->vmcb = page_address(vmcb_page);
svm->vmcb_pa = __sme_set(page_to_pfn(vmcb_page) << PAGE_SHIFT);
@@ -1229,10 +1236,6 @@ 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:
@@ -1258,10 +1261,10 @@ 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)
@@ -3919,6 +3922,7 @@ static int svm_pre_leave_smm(struct kvm_vcpu *vcpu, const char *smstate)
gpa_to_gfn(vmcb12_gpa), &map) == -EINVAL)
return 1;
+ svm_allocate_nested(svm);
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 468c58a915347..cb9c4a8f26f50 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 {
@@ -349,6 +351,8 @@ static inline bool gif_set(struct vcpu_svm *svm)
#define MSR_INVALID 0xffffffffU
u32 svm_msrpm_offset(u32 msr);
+u32 *svm_vcpu_init_msrpm(void);
+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);
@@ -390,6 +394,8 @@ 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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