linux-kernel - [RFC 07/19] KVM: x86/mmu: Factor wrprot for nested PML out of make

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Date:   Wed, 10 Nov 2021 14:29:58 -0800
From:   Ben Gardon <bgardon@...gle.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>, Peter Xu <peterx@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Peter Shier <pshier@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Mingwei Zhang <mizhang@...gle.com>,
        Yulei Zhang <yulei.kernel@...il.com>,
        Wanpeng Li <kernellwp@...il.com>,
        Xiao Guangrong <xiaoguangrong.eric@...il.com>,
        Kai Huang <kai.huang@...el.com>,
        Keqian Zhu <zhukeqian1@...wei.com>,
        David Hildenbrand <david@...hat.com>,
        Ben Gardon <bgardon@...gle.com>
Subject: [RFC 07/19] KVM: x86/mmu: Factor wrprot for nested PML out of make_spte

When running a nested VM, KVM write protects SPTEs in the EPT/NPT02
instead of using PML for dirty tracking. This avoids expensive
translation later, when emptying the Page Modification Log. In service
of removing the vCPU pointer from make_spte, factor the check for nested
PML out of the function.


Signed-off-by: Ben Gardon <bgardon@...gle.com>
---
 arch/x86/kvm/mmu/spte.c | 10 +++++++---
 arch/x86/kvm/mmu/spte.h |  3 ++-
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c
index 04d26e913941..3cf08a534a16 100644
--- a/arch/x86/kvm/mmu/spte.c
+++ b/arch/x86/kvm/mmu/spte.c
@@ -92,7 +92,8 @@ static bool kvm_is_mmio_pfn(kvm_pfn_t pfn)
 bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
 	       struct kvm_memory_slot *slot, unsigned int pte_access,
 	       gfn_t gfn, kvm_pfn_t pfn, u64 old_spte, bool prefetch,
-	       bool can_unsync, bool host_writable, u64 *new_spte)
+	       bool can_unsync, bool host_writable, bool ad_need_write_protect,
+	       u64 *new_spte)
 {
 	int level = sp->role.level;
 	u64 spte = SPTE_MMU_PRESENT_MASK;
@@ -100,7 +101,7 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
 
 	if (sp->role.ad_disabled)
 		spte |= SPTE_TDP_AD_DISABLED_MASK;
-	else if (kvm_vcpu_ad_need_write_protect(vcpu))
+	else if (ad_need_write_protect)
 		spte |= SPTE_TDP_AD_WRPROT_ONLY_MASK;
 
 	/*
@@ -195,8 +196,11 @@ bool vcpu_make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
 		    gfn_t gfn, kvm_pfn_t pfn, u64 old_spte, bool prefetch,
 		    bool can_unsync, bool host_writable, u64 *new_spte)
 {
+	bool ad_need_write_protect = kvm_vcpu_ad_need_write_protect(vcpu);
+
 	return make_spte(vcpu, sp, slot, pte_access, gfn, pfn, old_spte,
-			 prefetch, can_unsync, host_writable, new_spte);
+			 prefetch, can_unsync, host_writable,
+			 ad_need_write_protect, new_spte);
 
 }
 
diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
index 14f18082d505..bcf58602f224 100644
--- a/arch/x86/kvm/mmu/spte.h
+++ b/arch/x86/kvm/mmu/spte.h
@@ -332,7 +332,8 @@ static inline u64 get_mmio_spte_generation(u64 spte)
 bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
 	       struct kvm_memory_slot *slot, unsigned int pte_access,
 	       gfn_t gfn, kvm_pfn_t pfn, u64 old_spte, bool prefetch,
-	       bool can_unsync, bool host_writable, u64 *new_spte);
+	       bool can_unsync, bool host_writable, bool ad_need_write_protect,
+	       u64 *new_spte);
 bool vcpu_make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
 		    struct kvm_memory_slot *slot,
 		    unsigned int pte_access, gfn_t gfn, kvm_pfn_t pfn,
-- 
2.34.0.rc0.344.g81b53c2807-goog