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Subject[PATCH 5/6] KVM: nSVM: avoid loading PDPTRs after migration when possible
Date
if new KVM_*_SREGS2 ioctls are used, the PDPTRs are
part of the migration state and thus are loaded
by those ioctls.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
arch/x86/kvm/svm/nested.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index ac5e3e17bda4..b94916548cfa 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -373,10 +373,9 @@ static int nested_svm_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3,
return -EINVAL;

if (!nested_npt && is_pae_paging(vcpu) &&
- (cr3 != kvm_read_cr3(vcpu) || pdptrs_changed(vcpu))) {
+ (cr3 != kvm_read_cr3(vcpu) || !kvm_register_is_available(vcpu, VCPU_EXREG_PDPTR)))
if (CC(!load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3)))
return -EINVAL;
- }

/*
* TODO: optimize unconditional TLB flush/MMU sync here and in
@@ -552,6 +551,8 @@ int enter_svm_guest_mode(struct kvm_vcpu *vcpu, u64 vmcb12_gpa,
nested_vmcb02_prepare_control(svm);
nested_vmcb02_prepare_save(svm, vmcb12);

+ kvm_register_clear_available(&svm->vcpu, VCPU_EXREG_PDPTR);
+
ret = nested_svm_load_cr3(&svm->vcpu, vmcb12->save.cr3,
nested_npt_enabled(svm));
if (ret)
@@ -779,6 +780,8 @@ int nested_svm_vmexit(struct vcpu_svm *svm)

nested_svm_uninit_mmu_context(vcpu);

+ kvm_register_clear_available(&svm->vcpu, VCPU_EXREG_PDPTR);
+
rc = nested_svm_load_cr3(vcpu, svm->vmcb->save.cr3, false);
if (rc)
return 1;
@@ -1301,6 +1304,14 @@ static bool svm_get_nested_state_pages(struct kvm_vcpu *vcpu)
if (WARN_ON(!is_guest_mode(vcpu)))
return true;

+ if (vcpu->arch.reload_pdptrs_on_nested_entry) {
+ /* If legacy KVM_SET_SREGS API was used, it might have
+ * loaded wrong PDPTRs from memory so we have to reload
+ * them here (which is against x86 spec)
+ */
+ kvm_register_clear_available(vcpu, VCPU_EXREG_PDPTR);
+ }
+
if (nested_svm_load_cr3(&svm->vcpu, vcpu->arch.cr3,
nested_npt_enabled(svm)))
return false;
--
2.26.2
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