[PATCH 02/23] KVM: x86/mmu: Derive shadow MMU page role from parent

[David Matlack <dmatlack@google.com>]

Instead of computing the shadow page role from scratch for every new
page, we can derive most of the information from the parent shadow page.
This avoids redundant calculations such as the quadrant, and reduces the
number of parameters to kvm_mmu_get_page().

Preemptivel split out the role calculation to a separate function for
use in a following commit.

No functional change intended.

Signed-off-by: David Matlack <dmatlack@google.com>
---
 arch/x86/kvm/mmu/mmu.c         | 71 ++++++++++++++++++++++------------
 arch/x86/kvm/mmu/paging_tmpl.h |  9 +++--
 2 files changed, 51 insertions(+), 29 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 6ca38277f2ab..fc9a4d9c0ddd 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -2045,30 +2045,14 @@ static void clear_sp_write_flooding_count(u64 *spte)
 	__clear_sp_write_flooding_count(sptep_to_sp(spte));
 }
 
-static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
-					     gfn_t gfn,
-					     gva_t gaddr,
-					     unsigned level,
-					     int direct,
-					     unsigned int access)
+static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, gfn_t gfn,
+					     union kvm_mmu_page_role role)
 {
-	union kvm_mmu_page_role role;
 	struct hlist_head *sp_list;
-	unsigned quadrant;
 	struct kvm_mmu_page *sp;
 	int collisions = 0;
 	LIST_HEAD(invalid_list);
 
-	role = vcpu->arch.mmu->mmu_role.base;
-	role.level = level;
-	role.direct = direct;
-	role.access = access;
-	if (role.has_4_byte_gpte) {
-		quadrant = gaddr >> (PAGE_SHIFT + (PT64_PT_BITS * level));
-		quadrant &= (1 << ((PT32_PT_BITS - PT64_PT_BITS) * level)) - 1;
-		role.quadrant = quadrant;
-	}
-
 	sp_list = &vcpu->kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)];
 	for_each_valid_sp(vcpu->kvm, sp, sp_list) {
 		if (sp->gfn != gfn) {
@@ -2086,7 +2070,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
 			 * Unsync pages must not be left as is, because the new
 			 * upper-level page will be write-protected.
 			 */
-			if (level > PG_LEVEL_4K && sp->unsync)
+			if (role.level > PG_LEVEL_4K && sp->unsync)
 				kvm_mmu_prepare_zap_page(vcpu->kvm, sp,
 							 &invalid_list);
 			continue;
@@ -2125,14 +2109,14 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
 
 	++vcpu->kvm->stat.mmu_cache_miss;
 
-	sp = kvm_mmu_alloc_page(vcpu, direct);
+	sp = kvm_mmu_alloc_page(vcpu, role.direct);
 
 	sp->gfn = gfn;
 	sp->role = role;
 	hlist_add_head(&sp->hash_link, sp_list);
-	if (!direct) {
+	if (!role.direct) {
 		account_shadowed(vcpu->kvm, sp);
-		if (level == PG_LEVEL_4K && kvm_vcpu_write_protect_gfn(vcpu, gfn))
+		if (role.level == PG_LEVEL_4K && kvm_vcpu_write_protect_gfn(vcpu, gfn))
 			kvm_flush_remote_tlbs_with_address(vcpu->kvm, gfn, 1);
 	}
 	trace_kvm_mmu_get_page(sp, true);
@@ -2144,6 +2128,31 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
 	return sp;
 }
 
+static union kvm_mmu_page_role kvm_mmu_child_role(struct kvm_mmu_page *parent_sp,
+						  bool direct, u32 access)
+{
+	union kvm_mmu_page_role role;
+
+	role = parent_sp->role;
+	role.level--;
+	role.access = access;
+	role.direct = direct;
+
+	return role;
+}
+
+static struct kvm_mmu_page *kvm_mmu_get_child_sp(struct kvm_vcpu *vcpu,
+						 u64 *sptep, gfn_t gfn,
+						 bool direct, u32 access)
+{
+	struct kvm_mmu_page *parent_sp = sptep_to_sp(sptep);
+	union kvm_mmu_page_role role;
+
+	role = kvm_mmu_child_role(parent_sp, direct, access);
+
+	return kvm_mmu_get_page(vcpu, gfn, role);
+}
+
 static void shadow_walk_init_using_root(struct kvm_shadow_walk_iterator *iterator,
 					struct kvm_vcpu *vcpu, hpa_t root,
 					u64 addr)
@@ -2942,8 +2951,7 @@ static int __direct_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 		if (is_shadow_present_pte(*it.sptep))
 			continue;
 
-		sp = kvm_mmu_get_page(vcpu, base_gfn, it.addr,
-				      it.level - 1, true, ACC_ALL);
+		sp = kvm_mmu_get_child_sp(vcpu, it.sptep, base_gfn, true, ACC_ALL);
 
 		link_shadow_page(vcpu, it.sptep, sp);
 		if (fault->is_tdp && fault->huge_page_disallowed &&
@@ -3325,9 +3333,22 @@ static int mmu_check_root(struct kvm_vcpu *vcpu, gfn_t root_gfn)
 static hpa_t mmu_alloc_root(struct kvm_vcpu *vcpu, gfn_t gfn, gva_t gva,
 			    u8 level, bool direct)
 {
+	union kvm_mmu_page_role role;
 	struct kvm_mmu_page *sp;
+	unsigned int quadrant;
+
+	role = vcpu->arch.mmu->mmu_role.base;
+	role.level = level;
+	role.direct = direct;
+	role.access = ACC_ALL;
+
+	if (role.has_4_byte_gpte) {
+		quadrant = gva >> (PAGE_SHIFT + (PT64_PT_BITS * level));
+		quadrant &= (1 << ((PT32_PT_BITS - PT64_PT_BITS) * level)) - 1;
+		role.quadrant = quadrant;
+	}
 
-	sp = kvm_mmu_get_page(vcpu, gfn, gva, level, direct, ACC_ALL);
+	sp = kvm_mmu_get_page(vcpu, gfn, role);
 	++sp->root_count;
 
 	return __pa(sp->spt);
diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 5b5bdac97c7b..f93d4423a067 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -683,8 +683,9 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
 		if (!is_shadow_present_pte(*it.sptep)) {
 			table_gfn = gw->table_gfn[it.level - 2];
 			access = gw->pt_access[it.level - 2];
-			sp = kvm_mmu_get_page(vcpu, table_gfn, fault->addr,
-					      it.level-1, false, access);
+			sp = kvm_mmu_get_child_sp(vcpu, it.sptep, table_gfn,
+						  false, access);
+
 			/*
 			 * We must synchronize the pagetable before linking it
 			 * because the guest doesn't need to flush tlb when
@@ -740,8 +741,8 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
 		drop_large_spte(vcpu, it.sptep);
 
 		if (!is_shadow_present_pte(*it.sptep)) {
-			sp = kvm_mmu_get_page(vcpu, base_gfn, fault->addr,
-					      it.level - 1, true, direct_access);
+			sp = kvm_mmu_get_child_sp(vcpu, it.sptep, base_gfn,
+						  true, direct_access);
 			link_shadow_page(vcpu, it.sptep, sp);
 			if (fault->huge_page_disallowed &&
 			    fault->req_level >= it.level)
-- 
2.35.0.rc2.247.g8bbb082509-goog