KVM: x86/mmu: Pass memory caches to allocate SPs separately

Refactor kvm_mmu_alloc_shadow_page() to receive the caches from which it
will allocate the various pieces of memory for shadow pages as a
parameter, rather than deriving them from the vcpu pointer. This will be
useful in a future commit where shadow pages are allocated during VM
ioctls for eager page splitting, and thus will use a different set of
caches.

Preemptively pull the caches out all the way to
kvm_mmu_get_shadow_page() since eager page splitting will not be calling
kvm_mmu_alloc_shadow_page() directly.

No functional change intended.
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20220516232138.1783324-11-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/mmu.c

@@ -2049,17 +2049,25 @@ static struct kvm_mmu_page *kvm_mmu_find_shadow_page(struct kvm_vcpu *vcpu,
 	return sp;
 }
 
+/* Caches used when allocating a new shadow page. */
+struct shadow_page_caches {
+	struct kvm_mmu_memory_cache *page_header_cache;
+	struct kvm_mmu_memory_cache *shadow_page_cache;
+	struct kvm_mmu_memory_cache *gfn_array_cache;
+};
+
 static struct kvm_mmu_page *kvm_mmu_alloc_shadow_page(struct kvm_vcpu *vcpu,
+						      struct shadow_page_caches *caches,
 						      gfn_t gfn,
 						      struct hlist_head *sp_list,
 						      union kvm_mmu_page_role role)
 {
 	struct kvm_mmu_page *sp;
 
-	sp = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache);
-	sp->spt = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_shadow_page_cache);
+	sp = kvm_mmu_memory_cache_alloc(caches->page_header_cache);
+	sp->spt = kvm_mmu_memory_cache_alloc(caches->shadow_page_cache);
 	if (!role.direct)
-		sp->gfns = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_gfn_array_cache);
+		sp->gfns = kvm_mmu_memory_cache_alloc(caches->gfn_array_cache);
 
 	set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
 
@@ -2081,7 +2089,8 @@ static struct kvm_mmu_page *kvm_mmu_alloc_shadow_page(struct kvm_vcpu *vcpu,
 	return sp;
 }
 
-static struct kvm_mmu_page *kvm_mmu_get_shadow_page(struct kvm_vcpu *vcpu,
+static struct kvm_mmu_page *__kvm_mmu_get_shadow_page(struct kvm_vcpu *vcpu,
+						      struct shadow_page_caches *caches,
 						      gfn_t gfn,
 						      union kvm_mmu_page_role role)
 {
@@ -2094,13 +2103,26 @@ static struct kvm_mmu_page *kvm_mmu_get_shadow_page(struct kvm_vcpu *vcpu,
 	sp = kvm_mmu_find_shadow_page(vcpu, gfn, sp_list, role);
 	if (!sp) {
 		created = true;
-		sp = kvm_mmu_alloc_shadow_page(vcpu, gfn, sp_list, role);
+		sp = kvm_mmu_alloc_shadow_page(vcpu, caches, gfn, sp_list, role);
 	}
 
 	trace_kvm_mmu_get_page(sp, created);
 	return sp;
 }
 
+static struct kvm_mmu_page *kvm_mmu_get_shadow_page(struct kvm_vcpu *vcpu,
+						    gfn_t gfn,
+						    union kvm_mmu_page_role role)
+{
+	struct shadow_page_caches caches = {
+		.page_header_cache = &vcpu->arch.mmu_page_header_cache,
+		.shadow_page_cache = &vcpu->arch.mmu_shadow_page_cache,
+		.gfn_array_cache = &vcpu->arch.mmu_gfn_array_cache,
+	};
+
+	return __kvm_mmu_get_shadow_page(vcpu, &caches, gfn, role);
+}
+
 static union kvm_mmu_page_role kvm_mmu_child_role(u64 *sptep, bool direct, unsigned int access)
 {
 	struct kvm_mmu_page *parent_sp = sptep_to_sp(sptep);