linux-kernel - [RFC PATCH 1/6] KVM: x86/mmu: Add hook to pin PFNs on demand in MMU

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Message-ID: <20220118110621.62462-2-nikunj@amd.com>
Date:   Tue, 18 Jan 2022 16:36:16 +0530
From:   Nikunj A Dadhania <nikunj@....com>
To:     Paolo Bonzini <pbonzini@...hat.com>
CC:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Brijesh Singh <brijesh.singh@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Peter Gonda <pgonda@...gle.com>, <kvm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Nikunj A Dadhania <nikunj@....com>
Subject: [RFC PATCH 1/6] KVM: x86/mmu: Add hook to pin PFNs on demand in MMU

Use vendor code via kvm_x86_ops hooks for pinning.

Signed-off-by: Nikunj A Dadhania <nikunj@....com>
---
 arch/x86/include/asm/kvm-x86-ops.h | 1 +
 arch/x86/include/asm/kvm_host.h    | 2 ++
 arch/x86/kvm/mmu/mmu.c             | 3 +++
 arch/x86/kvm/mmu/tdp_mmu.c         | 7 +++++++
 4 files changed, 13 insertions(+)

diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index f658bb4dbb74..a96c52a99a04 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -87,6 +87,7 @@ KVM_X86_OP(set_tss_addr)
 KVM_X86_OP(set_identity_map_addr)
 KVM_X86_OP(get_mt_mask)
 KVM_X86_OP(load_mmu_pgd)
+KVM_X86_OP(pin_spte)
 KVM_X86_OP_NULL(has_wbinvd_exit)
 KVM_X86_OP(get_l2_tsc_offset)
 KVM_X86_OP(get_l2_tsc_multiplier)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 0677b9ea01c9..1263a16dd588 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1417,6 +1417,8 @@ struct kvm_x86_ops {
 
 	void (*load_mmu_pgd)(struct kvm_vcpu *vcpu, hpa_t root_hpa,
 			     int root_level);
+	void (*pin_spte)(struct kvm *kvm, gfn_t gfn, enum pg_level level,
+			 kvm_pfn_t pfn);
 
 	bool (*has_wbinvd_exit)(void);
 
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 1d275e9d76b5..62dda588eb99 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -2977,6 +2977,9 @@ static int __direct_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 		return ret;
 
 	direct_pte_prefetch(vcpu, it.sptep);
+	if (!is_error_noslot_pfn(fault->pfn) && !kvm_is_reserved_pfn(fault->pfn))
+		static_call_cond(kvm_x86_pin_spte)(vcpu->kvm, base_gfn,
+						   it.level, fault->pfn);
 	++vcpu->stat.pf_fixed;
 	return ret;
 }
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 7b1bc816b7c3..b7578fa02e9f 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -467,6 +467,13 @@ static void __handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
 	    (!is_present || !is_dirty_spte(new_spte) || pfn_changed))
 		kvm_set_pfn_dirty(spte_to_pfn(old_spte));
 
+	/*
+	 * Call the vendor code to handle the pinning
+	 */
+	if (is_present && is_leaf)
+		static_call_cond(kvm_x86_pin_spte)(kvm, gfn, level,
+						   spte_to_pfn(new_spte));
+
 	/*
 	 * Recursively handle child PTs if the change removed a subtree from
 	 * the paging structure.
-- 
2.32.0