linux-kernel - [RFC PATCH 43/67] KVM: x86/mmu: Introduce kvm_mmu_map_tdp

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Date:   Mon, 16 Nov 2020 10:26:28 -0800
From:   isaku.yamahata@...el.com
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     isaku.yamahata@...el.com, isaku.yamahata@...il.com,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: [RFC PATCH 43/67] KVM: x86/mmu: Introduce kvm_mmu_map_tdp_page() for use by TDX

From: Sean Christopherson <sean.j.christopherson@...el.com>

Introduce a helper to directly (pun intented) fault-in a TDP page
without having to go through the full page fault path.  This allows
TDX to get the resulting pfn and also allows the RET_PF_* enums to
stay in mmu.c where they belong.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/mmu.h     |  3 +++
 arch/x86/kvm/mmu/mmu.c | 25 +++++++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 3b1243cfc280..a6bb930d1549 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -115,6 +115,9 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 	return vcpu->arch.mmu->page_fault(vcpu, cr2_or_gpa, err, prefault);
 }
 
+kvm_pfn_t kvm_mmu_map_tdp_page(struct kvm_vcpu *vcpu, gpa_t gpa,
+			       u32 error_code, int max_level);
+
 /*
  * Currently, we have two sorts of write-protection, a) the first one
  * write-protects guest page to sync the guest modification, b) another one is
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 474173bceb54..bb59e80ade81 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4034,6 +4034,31 @@ int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
 				 max_level, true, &pfn);
 }
 
+kvm_pfn_t kvm_mmu_map_tdp_page(struct kvm_vcpu *vcpu, gpa_t gpa,
+			       u32 error_code, int max_level)
+{
+	kvm_pfn_t pfn;
+	int r;
+
+	if (mmu_topup_memory_caches(vcpu, false))
+		return KVM_PFN_ERR_FAULT;
+
+	/*
+	 * Loop on the page fault path to handle the case where an mmu_notifier
+	 * invalidation triggers RET_PF_RETRY.  In the normal page fault path,
+	 * KVM needs to resume the guest in case the invalidation changed any
+	 * of the page fault properties, i.e. the gpa or error code.  For this
+	 * path, the gpa and error code are fixed by the caller, and the caller
+	 * expects failure if and only if the page fault can't be fixed.
+	 */
+	do {
+		r = direct_page_fault(vcpu, gpa, error_code, false, max_level,
+				      true, &pfn);
+	} while (r == RET_PF_RETRY && !is_error_noslot_pfn(pfn));
+	return pfn;
+}
+EXPORT_SYMBOL_GPL(kvm_mmu_map_tdp_page);
+
 static void nonpaging_init_context(struct kvm_vcpu *vcpu,
 				   struct kvm_mmu *context)
 {
-- 
2.17.1