linux-kernel - [RFC PATCH 5/8] KVM: SVM: Use the KVM MMU SPTE pinning hooks to pin pages on demand

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Date:   Fri, 31 Jul 2020 14:23:20 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        eric van tassell <Eric.VanTassell@....com>,
        Tom Lendacky <thomas.lendacky@....com>
Subject: [RFC PATCH 5/8] KVM: SVM: Use the KVM MMU SPTE pinning hooks to pin pages on demand

Cc: eric van tassell <Eric.VanTassell@....com>
Cc: Tom Lendacky <thomas.lendacky@....com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/svm/sev.c | 24 ++++++++++++++++++++++++
 arch/x86/kvm/svm/svm.c |  3 +++
 arch/x86/kvm/svm/svm.h |  3 +++
 3 files changed, 30 insertions(+)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index f7f1f4ecf08e3..f640b8beb443e 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1193,3 +1193,27 @@ void pre_sev_run(struct vcpu_svm *svm, int cpu)
 	svm->vmcb->control.tlb_ctl = TLB_CONTROL_FLUSH_ASID;
 	vmcb_mark_dirty(svm->vmcb, VMCB_ASID);
 }
+
+bool sev_pin_spte(struct kvm_vcpu *vcpu, gfn_t gfn, int level, kvm_pfn_t pfn)
+{
+	if (!sev_guest(vcpu->kvm))
+		return false;
+
+	get_page(pfn_to_page(pfn));
+
+	/*
+	 * Flush any cached lines of the page being added since "ownership" of
+	 * it will be transferred from the host to an encrypted guest.
+	 */
+	clflush_cache_range(__va(pfn << PAGE_SHIFT), page_level_size(level));
+
+	return true;
+}
+
+void sev_drop_pinned_spte(struct kvm *kvm, gfn_t gfn, int level, kvm_pfn_t pfn)
+{
+	if (WARN_ON_ONCE(!sev_guest(kvm)))
+		return;
+
+	put_page(pfn_to_page(pfn));
+}
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 0ae20af3a1677..a9f7515b4eff3 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4150,6 +4150,9 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
 	.need_emulation_on_page_fault = svm_need_emulation_on_page_fault,
 
 	.apic_init_signal_blocked = svm_apic_init_signal_blocked,
+
+	.pin_spte = sev_pin_spte,
+	.drop_pinned_spte = sev_drop_pinned_spte,
 };
 
 static struct kvm_x86_init_ops svm_init_ops __initdata = {
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index a798e17317094..3060e3e529cbc 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -489,4 +489,7 @@ void pre_sev_run(struct vcpu_svm *svm, int cpu);
 int __init sev_hardware_setup(void);
 void sev_hardware_teardown(void);
 
+bool sev_pin_spte(struct kvm_vcpu *vcpu, gfn_t gfn, int level, kvm_pfn_t pfn);
+void sev_drop_pinned_spte(struct kvm *kvm, gfn_t gfn, int level, kvm_pfn_t pfn);
+
 #endif
-- 
2.28.0