From: Maxim Levitsky <mlevitsk@redhat.com>
To: kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>,
linux-kernel@vger.kernel.org (open list),
linux-doc@vger.kernel.org (open list:DOCUMENTATION),
Wanpeng Li <wanpengli@tencent.com>,
Ingo Molnar <mingo@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Sean Christopherson <seanjc@google.com>,
Borislav Petkov <bp@alien8.de>, Joerg Roedel <joro@8bytes.org>,
x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
Jim Mattson <jmattson@google.com>,
Jonathan Corbet <corbet@lwn.net>,
"H. Peter Anvin" <hpa@zytor.com>,
Maxim Levitsky <mlevitsk@redhat.com>
Subject: [PATCH v3 4/8] KVM: nSVM: refactor the CR3 reload on migration
Date: Mon, 7 Jun 2021 12:01:59 +0300 [thread overview]
Message-ID: <20210607090203.133058-5-mlevitsk@redhat.com> (raw)
In-Reply-To: <20210607090203.133058-1-mlevitsk@redhat.com>
Document the actual reason why we need to do it
on migration and move the call to svm_set_nested_state
to be closer to VMX code.
To avoid loading the PDPTRs from possibly not up to date memory map,
in nested_svm_load_cr3 after the move, move this code to
.get_nested_state_pages.
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
arch/x86/kvm/svm/nested.c | 32 +++++++++++++++++++++++++-------
1 file changed, 25 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 8f5dbc80f57f..e3e5775b8f1c 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -385,12 +385,12 @@ static inline bool nested_npt_enabled(struct vcpu_svm *svm)
* if we are emulating VM-Entry into a guest with NPT enabled.
*/
static int nested_svm_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3,
- bool nested_npt)
+ bool nested_npt, bool reload_pdptrs)
{
if (CC(kvm_vcpu_is_illegal_gpa(vcpu, cr3)))
return -EINVAL;
- if (!nested_npt && is_pae_paging(vcpu) &&
+ if (reload_pdptrs && !nested_npt && is_pae_paging(vcpu) &&
CC(!load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3)))
return -EINVAL;
@@ -574,7 +574,7 @@ int enter_svm_guest_mode(struct kvm_vcpu *vcpu, u64 vmcb12_gpa,
nested_vmcb02_prepare_save(svm, vmcb12);
ret = nested_svm_load_cr3(&svm->vcpu, vmcb12->save.cr3,
- nested_npt_enabled(svm));
+ nested_npt_enabled(svm), true);
if (ret)
return ret;
@@ -803,7 +803,7 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
nested_svm_uninit_mmu_context(vcpu);
- rc = nested_svm_load_cr3(vcpu, svm->vmcb->save.cr3, false);
+ rc = nested_svm_load_cr3(vcpu, svm->vmcb->save.cr3, false, true);
if (rc)
return 1;
@@ -1299,6 +1299,19 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
!nested_vmcb_valid_sregs(vcpu, save))
goto out_free;
+ /*
+ * While the nested guest CR3 is already checked and set by
+ * KVM_SET_SREGS, it was set when nested state was yet loaded,
+ * thus MMU might not be initialized correctly.
+ * Set it again to fix this.
+ */
+
+ ret = nested_svm_load_cr3(&svm->vcpu, vcpu->arch.cr3,
+ nested_npt_enabled(svm), false);
+ if (WARN_ON_ONCE(ret))
+ goto out_free;
+
+
/*
* All checks done, we can enter guest mode. Userspace provides
* vmcb12.control, which will be combined with L1 and stored into
@@ -1356,9 +1369,14 @@ static bool svm_get_nested_state_pages(struct kvm_vcpu *vcpu)
if (WARN_ON(!is_guest_mode(vcpu)))
return true;
- if (nested_svm_load_cr3(&svm->vcpu, vcpu->arch.cr3,
- nested_npt_enabled(svm)))
- return false;
+ if (!nested_npt_enabled(svm) && is_pae_paging(vcpu))
+ /*
+ * Reload the guest's PDPTRs since after a migration
+ * the guest CR3 might be restored prior to setting the nested
+ * state which can lead to a load of wrong PDPTRs.
+ */
+ if (CC(!load_pdptrs(vcpu, vcpu->arch.walk_mmu, vcpu->arch.cr3)))
+ return false;
if (!nested_svm_vmrun_msrpm(svm)) {
vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
--
2.26.3
next prev parent reply other threads:[~2021-06-07 9:02 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-07 9:01 [PATCH v3 0/8] Introduce KVM_{GET|SET}_SREGS2 and fix PDPTR migration Maxim Levitsky
2021-06-07 9:01 ` [PATCH v3 1/8] KVM: nVMX: Drop obsolete (and pointless) pdptrs_changed() check Maxim Levitsky
2021-06-07 9:01 ` [PATCH v3 2/8] KVM: nSVM: Drop pointless pdptrs_changed() check on nested transition Maxim Levitsky
2021-06-07 9:01 ` [PATCH v3 3/8] KVM: x86: Always load PDPTRs on CR3 load for SVM w/o NPT and a PAE guest Maxim Levitsky
2021-06-07 9:01 ` Maxim Levitsky [this message]
2021-06-07 9:02 ` [PATCH v3 5/8] KVM: nVMX: delay loading of PDPTRs to KVM_REQ_GET_NESTED_STATE_PAGES Maxim Levitsky
2021-06-07 9:02 ` [PATCH v3 6/8] KVM: x86: introduce kvm_register_clear_available Maxim Levitsky
2021-06-07 9:02 ` [PATCH v3 7/8] KVM: x86: Introduce KVM_GET_SREGS2 / KVM_SET_SREGS2 Maxim Levitsky
2021-06-10 15:06 ` Paolo Bonzini
2021-06-07 9:02 ` [PATCH v3 8/8] KVM: x86: avoid loading PDPTRs after migration when possible Maxim Levitsky
2021-06-18 20:53 ` Sean Christopherson
2021-06-19 7:03 ` Paolo Bonzini
2021-06-20 22:25 ` Maxim Levitsky
2021-06-10 15:06 ` [PATCH v3 0/8] Introduce KVM_{GET|SET}_SREGS2 and fix PDPTR migration Paolo Bonzini
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