linux-kernel - [PATCH v2 6/6] KVM: nVMX: avoid loading PDPTRs after migration when possible

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Date:   Mon, 26 Apr 2021 14:13:33 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     kvm@...r.kernel.org
Cc:     linux-doc@...r.kernel.org (open list:DOCUMENTATION),
        Thomas Gleixner <tglx@...utronix.de>,
        Jonathan Corbet <corbet@....net>,
        Paolo Bonzini <pbonzini@...hat.com>,
        x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
        linux-kernel@...r.kernel.org (open list:X86 ARCHITECTURE (32-BIT AND
        64-BIT)), "H. Peter Anvin" <hpa@...or.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH v2 6/6] KVM: nVMX: avoid loading PDPTRs after migration when possible

if new KVM_*_SREGS2 ioctls are used, the PDPTRs are
a part of the migration state and are correctly
restored by those ioctls.

Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 arch/x86/kvm/vmx/nested.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 764781ab805b..743a832d6caf 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3122,7 +3122,8 @@ static bool nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
 	struct page *page;
 	u64 hpa;
 
-	if (!nested_cpu_has_ept(vmcs12) && is_pae_paging(vcpu)) {
+	if (vcpu->arch.pdptr_reload_on_nesting_needed &&
+	    !nested_cpu_has_ept(vmcs12) && is_pae_paging(vcpu)) {
 		/*
 		 * Reload the guest's PDPTRs since after a migration
 		 * the guest CR3 might be restored prior to setting the nested
-- 
2.26.2