linux-kernel - [PATCH Part2 v6 30/49] KVM: x86/mmu: Introduce kvm_mmu_map_tdp

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Date:   Mon, 20 Jun 2022 23:09:20 +0000
From:   Ashish Kalra <Ashish.Kalra@....com>
To:     <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
        <kvm@...r.kernel.org>, <linux-coco@...ts.linux.dev>,
        <linux-mm@...ck.org>, <linux-crypto@...r.kernel.org>
CC:     <tglx@...utronix.de>, <mingo@...hat.com>, <jroedel@...e.de>,
        <thomas.lendacky@....com>, <hpa@...or.com>, <ardb@...nel.org>,
        <pbonzini@...hat.com>, <seanjc@...gle.com>, <vkuznets@...hat.com>,
        <jmattson@...gle.com>, <luto@...nel.org>,
        <dave.hansen@...ux.intel.com>, <slp@...hat.com>,
        <pgonda@...gle.com>, <peterz@...radead.org>,
        <srinivas.pandruvada@...ux.intel.com>, <rientjes@...gle.com>,
        <dovmurik@...ux.ibm.com>, <tobin@....com>, <bp@...en8.de>,
        <michael.roth@....com>, <vbabka@...e.cz>, <kirill@...temov.name>,
        <ak@...ux.intel.com>, <tony.luck@...el.com>, <marcorr@...gle.com>,
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        <alpergun@...gle.com>, <dgilbert@...hat.com>, <jarkko@...nel.org>
Subject: [PATCH Part2 v6 30/49] KVM: x86/mmu: Introduce kvm_mmu_map_tdp_page() for use by TDX and SNP

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>
Signed-off-by: Brijesh Singh <brijesh.singh@....com>
---
 arch/x86/kvm/mmu.h     |  3 +++
 arch/x86/kvm/mmu/mmu.c | 51 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index e6cae6f22683..c99b15e97a0a 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -204,6 +204,9 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 	return vcpu->arch.mmu->page_fault(vcpu, &fault);
 }
 
+kvm_pfn_t kvm_mmu_map_tdp_page(struct kvm_vcpu *vcpu, gpa_t gpa,
+			       u32 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 997318ecebd1..569021af349a 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4100,6 +4100,57 @@ int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 	return direct_page_fault(vcpu, fault);
 }
 
+kvm_pfn_t kvm_mmu_map_tdp_page(struct kvm_vcpu *vcpu, gpa_t gpa,
+			       u32 err, int max_level)
+{
+	struct kvm_page_fault fault = {
+		.addr = gpa,
+		.error_code = err,
+		.exec = err & PFERR_FETCH_MASK,
+		.write = err & PFERR_WRITE_MASK,
+		.present = err & PFERR_PRESENT_MASK,
+		.rsvd = err & PFERR_RSVD_MASK,
+		.user = err & PFERR_USER_MASK,
+		.prefetch = false,
+		.is_tdp = likely(vcpu->arch.mmu->page_fault == kvm_tdp_page_fault),
+		.nx_huge_page_workaround_enabled = is_nx_huge_page_enabled(),
+
+		.max_level = max_level,
+		.req_level = PG_LEVEL_4K,
+		.goal_level = PG_LEVEL_4K,
+	};
+	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 {
+		/*
+		 * TODO: this should probably go through kvm_mmu_do_page_fault(),
+		 * but we need a way to control the max_level, so maybe a direct
+		 * call to kvm_tdp_page_fault, which will call into
+		 * direct_page_fault() when appropriate.
+		 */
+		//r = direct_page_fault(vcpu, &fault);
+#if CONFIG_RETPOLINE
+		if (fault.is_tdp)
+			r = kvm_tdp_page_fault(vcpu, &fault);
+#else
+		r = vcpu->arch.mmu->page_fault(vcpu, &fault);
+#endif
+	} while (r == RET_PF_RETRY && !is_error_noslot_pfn(fault.pfn));
+	return fault.pfn;
+}
+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