linux-kernel - [PATCH 6/7] KVM: nVMX: don't load PDPTRS right after nested state set

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Date:   Wed, 17 Feb 2021 16:57:17 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Wanpeng Li <wanpengli@...cent.com>,
        Borislav Petkov <bp@...en8.de>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Jim Mattson <jmattson@...gle.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Sean Christopherson <seanjc@...gle.com>,
        x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
        Thomas Gleixner <tglx@...utronix.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 6/7] KVM: nVMX: don't load PDPTRS right after nested state set

Just like all other nested memory accesses, after a migration loading
PDPTRs should be delayed to first VM entry to ensure
that guest memory is fully initialized.

Just move the call to nested_vmx_load_cr3 to nested_get_vmcs12_pages
to implement this.

Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 arch/x86/kvm/vmx/nested.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index f9de729dbea6..26084f8eee82 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2596,11 +2596,6 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 		return -EINVAL;
 	}
 
-	/* Shadow page tables on either EPT or shadow page tables. */
-	if (nested_vmx_load_cr3(vcpu, vmcs12->guest_cr3, nested_cpu_has_ept(vmcs12),
-				entry_failure_code))
-		return -EINVAL;
-
 	/*
 	 * Immediately write vmcs02.GUEST_CR3.  It will be propagated to vmcs12
 	 * on nested VM-Exit, which can occur without actually running L2 and
@@ -3138,11 +3133,16 @@ static bool nested_get_evmcs_page(struct kvm_vcpu *vcpu)
 static bool nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
 {
 	struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
+	enum vm_entry_failure_code entry_failure_code;
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	struct kvm_host_map *map;
 	struct page *page;
 	u64 hpa;
 
+	if (nested_vmx_load_cr3(vcpu, vmcs12->guest_cr3, nested_cpu_has_ept(vmcs12),
+				&entry_failure_code))
+		return false;
+
 	if (nested_cpu_has2(vmcs12, SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES)) {
 		/*
 		 * Translate L1 physical address to host physical
@@ -3386,6 +3386,10 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
 	}
 
 	if (from_vmentry) {
+		if (nested_vmx_load_cr3(vcpu, vmcs12->guest_cr3,
+		    nested_cpu_has_ept(vmcs12), &entry_failure_code))
+			goto vmentry_fail_vmexit_guest_mode;
+
 		failed_index = nested_vmx_load_msr(vcpu,
 						   vmcs12->vm_entry_msr_load_addr,
 						   vmcs12->vm_entry_msr_load_count);
-- 
2.26.2