linux-kernel - [PATCH v2 05/10] KVM: x86/mmu: Introduce kvm_tdp_map

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Message-ID: <9b866a0ae7147f96571c439e75429a03dcb659b6.1712785629.git.isaku.yamahata@intel.com>
Date: Wed, 10 Apr 2024 15:07:31 -0700
From: isaku.yamahata@...el.com
To: kvm@...r.kernel.org
Cc: isaku.yamahata@...el.com,
	isaku.yamahata@...il.com,
	linux-kernel@...r.kernel.org,
	Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Michael Roth <michael.roth@....com>,
	David Matlack <dmatlack@...gle.com>,
	Federico Parola <federico.parola@...ito.it>,
	Kai Huang <kai.huang@...el.com>
Subject: [PATCH v2 05/10] KVM: x86/mmu: Introduce kvm_tdp_map_page() to populate guest memory

From: Isaku Yamahata <isaku.yamahata@...el.com>

Introduce a helper function to call the KVM fault handler.  It allows a new
ioctl to invoke the KVM fault handler to populate without seeing RET_PF_*
enums or other KVM MMU internal definitions because RET_PF_* are internal
to x86 KVM MMU.  The implementation is restricted to two-dimensional paging
for simplicity.  The shadow paging uses GVA for faulting instead of L1 GPA.
It makes the API difficult to use.

Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
---
v2:
- Make the helper function two-dimensional paging specific. (David)
- Return error when vcpu is in guest mode. (David)
- Rename goal_level to level in kvm_tdp_mmu_map_page(). (Sean)
- Update return code conversion. Don't check pfn.
  RET_PF_EMULATE => EINVAL, RET_PF_CONTINUE => EIO (Sean)
- Add WARN_ON_ONCE on RET_PF_CONTINUE and RET_PF_INVALID. (Sean)
- Drop unnecessary EXPORT_SYMBOL_GPL(). (Sean)
---
 arch/x86/kvm/mmu.h     |  3 +++
 arch/x86/kvm/mmu/mmu.c | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index e8b620a85627..51ff4f67e115 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -183,6 +183,9 @@ static inline void kvm_mmu_refresh_passthrough_bits(struct kvm_vcpu *vcpu,
 	__kvm_mmu_refresh_passthrough_bits(vcpu, mmu);
 }
 
+int kvm_tdp_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code,
+		     u8 *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 91dd4c44b7d8..a34f4af44cbd 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4687,6 +4687,38 @@ int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 	return direct_page_fault(vcpu, fault);
 }
 
+int kvm_tdp_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code,
+		     u8 *level)
+{
+	int r;
+
+	/* Restrict to TDP page fault. */
+	if (vcpu->arch.mmu->page_fault != kvm_tdp_page_fault)
+		return -EINVAL;
+
+	r = __kvm_mmu_do_page_fault(vcpu, gpa, error_code, false, NULL, level);
+	if (r < 0)
+		return r;
+
+	switch (r) {
+	case RET_PF_RETRY:
+		return -EAGAIN;
+
+	case RET_PF_FIXED:
+	case RET_PF_SPURIOUS:
+		return 0;
+
+	case RET_PF_EMULATE:
+		return -EINVAL;
+
+	case RET_PF_CONTINUE:
+	case RET_PF_INVALID:
+	default:
+		WARN_ON_ONCE(r);
+		return -EIO;
+	}
+}
+
 static void nonpaging_init_context(struct kvm_mmu *context)
 {
 	context->page_fault = nonpaging_page_fault;
-- 
2.43.2