linux-kernel - [PATCH v16 058/116] KVM: x86/mmu: Introduce kvm_mmu_map_tdp

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Message-Id: <f3e7aa9b54bcfe0fb62fe4819fa1b01e6fba5cb5.1697471314.git.isaku.yamahata@intel.com>
Date:   Mon, 16 Oct 2023 09:14:10 -0700
From:   isaku.yamahata@...el.com
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...el.com, isaku.yamahata@...il.com,
        Paolo Bonzini <pbonzini@...hat.com>, erdemaktas@...gle.com,
        Sean Christopherson <seanjc@...gle.com>,
        Sagi Shahar <sagis@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Kai Huang <kai.huang@...el.com>,
        Zhi Wang <zhi.wang.linux@...il.com>, chen.bo@...el.com,
        hang.yuan@...el.com, tina.zhang@...el.com,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: [PATCH v16 058/116] 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 intended) 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>
Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
---
v14 -> v15:
- Remove loop in kvm_mmu_map_tdp_page() and return error code based on
  RET_FP_xxx value to avoid potential infinite loop.  The caller should
  loop on -EAGAIN instead now.
---
 arch/x86/kvm/mmu.h     |  3 +++
 arch/x86/kvm/mmu/mmu.c | 57 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 60 insertions(+)

diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index c30fefa39bb4..cb332d90c57f 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -176,6 +176,9 @@ static inline void kvm_mmu_refresh_passthrough_bits(struct kvm_vcpu *vcpu,
 	__kvm_mmu_refresh_passthrough_bits(vcpu, mmu);
 }
 
+int kvm_mmu_map_tdp_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code,
+			 int max_level);
+
 /*
  * Check if a given access (described through the I/D, W/R and U/S bits of a
  * page fault error code pfec) causes a permission fault with the given PTE
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 91250b2a7081..107cf27505fe 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4624,6 +4624,63 @@ int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 	return direct_page_fault(vcpu, fault);
 }
 
+int kvm_mmu_map_tdp_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code,
+			 int max_level)
+{
+	int r;
+	struct kvm_page_fault fault = (struct kvm_page_fault) {
+		.addr = gpa,
+		.error_code = error_code,
+		.exec = error_code & PFERR_FETCH_MASK,
+		.write = error_code & PFERR_WRITE_MASK,
+		.present = error_code & PFERR_PRESENT_MASK,
+		.rsvd = error_code & PFERR_RSVD_MASK,
+		.user = error_code & PFERR_USER_MASK,
+		.prefetch = false,
+		.is_tdp = true,
+		.is_private = error_code & PFERR_GUEST_ENC_MASK,
+		.nx_huge_page_workaround_enabled = is_nx_huge_page_enabled(vcpu->kvm),
+	};
+
+	WARN_ON_ONCE(!vcpu->arch.mmu->root_role.direct);
+	fault.gfn = gpa_to_gfn(fault.addr) & ~kvm_gfn_shared_mask(vcpu->kvm);
+	fault.slot = kvm_vcpu_gfn_to_memslot(vcpu, fault.gfn);
+
+	r = mmu_topup_memory_caches(vcpu, false);
+	if (r)
+		return r;
+
+	fault.max_level = max_level;
+	fault.req_level = PG_LEVEL_4K;
+	fault.goal_level = PG_LEVEL_4K;
+
+#ifdef CONFIG_X86_64
+	if (tdp_mmu_enabled)
+		r = kvm_tdp_mmu_page_fault(vcpu, &fault);
+	else
+#endif
+		r = direct_page_fault(vcpu, &fault);
+
+	if (is_error_noslot_pfn(fault.pfn) || vcpu->kvm->vm_bugged)
+		return -EFAULT;
+
+	switch (r) {
+	case RET_PF_RETRY:
+		return -EAGAIN;
+
+	case RET_PF_FIXED:
+	case RET_PF_SPURIOUS:
+		return 0;
+
+	case RET_PF_CONTINUE:
+	case RET_PF_EMULATE:
+	case RET_PF_INVALID:
+	default:
+		return -EIO;
+	}
+}
+EXPORT_SYMBOL_GPL(kvm_mmu_map_tdp_page);
+
 static void nonpaging_init_context(struct kvm_mmu *context)
 {
 	context->page_fault = nonpaging_page_fault;
-- 
2.25.1