KVM: x86/mmu: Decompose kvm_mmu_get_page() into separate functions

Decompose kvm_mmu_get_page() into separate helper functions to increase
readability and prepare for allocating shadow pages without a vcpu
pointer.

Specifically, pull the guts of kvm_mmu_get_page() into 2 helper
functions:

kvm_mmu_find_shadow_page() -
  Walks the page hash checking for any existing mmu pages that match the
  given gfn and role.

kvm_mmu_alloc_shadow_page()
  Allocates and initializes an entirely new kvm_mmu_page. This currently
  requries a vcpu pointer for allocation and looking up the memslot but
  that will be removed in a future commit.

No functional change intended.

Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20220516232138.1783324-7-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index f4e7978..a59fe86 100644 (file)
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -1993,16 +1993,16 @@ 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,
-                                            union kvm_mmu_page_role role)
+static struct kvm_mmu_page *kvm_mmu_find_shadow_page(struct kvm_vcpu *vcpu,
+                                                    gfn_t gfn,
+                                                    struct hlist_head *sp_list,
+                                                    union kvm_mmu_page_role role)
 {
-       struct hlist_head *sp_list;
        struct kvm_mmu_page *sp;
        int ret;
        int collisions = 0;
        LIST_HEAD(invalid_list);
 
-       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) {
                        collisions++;
@@ -2027,7 +2027,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, gfn_t gfn,
 
                /* unsync and write-flooding only apply to indirect SPs. */
                if (sp->role.direct)
-                       goto trace_get_page;
+                       goto out;
 
                if (sp->unsync) {
                        /*
@@ -2053,14 +2053,26 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, gfn_t gfn,
 
                __clear_sp_write_flooding_count(sp);
 
-trace_get_page:
-               trace_kvm_mmu_get_page(sp, false);
                goto out;
        }
 
+       sp = NULL;
        ++vcpu->kvm->stat.mmu_cache_miss;
 
-       sp = kvm_mmu_alloc_page(vcpu, role.direct);
+out:
+       kvm_mmu_commit_zap_page(vcpu->kvm, &invalid_list);
+
+       if (collisions > vcpu->kvm->stat.max_mmu_page_hash_collisions)
+               vcpu->kvm->stat.max_mmu_page_hash_collisions = collisions;
+       return sp;
+}
+
+static struct kvm_mmu_page *kvm_mmu_alloc_shadow_page(struct kvm_vcpu *vcpu,
+                                                     gfn_t gfn,
+                                                     struct hlist_head *sp_list,
+                                                     union kvm_mmu_page_role role)
+{
+       struct kvm_mmu_page *sp = kvm_mmu_alloc_page(vcpu, role.direct);
 
        sp->gfn = gfn;
        sp->role = role;
@@ -2070,12 +2082,26 @@ trace_get_page:
                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);
-out:
-       kvm_mmu_commit_zap_page(vcpu->kvm, &invalid_list);
 
-       if (collisions > vcpu->kvm->stat.max_mmu_page_hash_collisions)
-               vcpu->kvm->stat.max_mmu_page_hash_collisions = collisions;
+       return sp;
+}
+
+static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, gfn_t gfn,
+                                            union kvm_mmu_page_role role)
+{
+       struct hlist_head *sp_list;
+       struct kvm_mmu_page *sp;
+       bool created = false;
+
+       sp_list = &vcpu->kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)];
+
+       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);
+       }
+
+       trace_kvm_mmu_get_page(sp, created);
        return sp;
 }