[PATCH v12 48/84] KVM: Move x86's API to release a faultin page to common KVM

[Sean Christopherson]

Move KVM x86's helper that "finishes" the faultin process to common KVM
so that the logic can be shared across all architectures.  Note, not all
architectures implement a fast page fault path, but the gist of the
comment applies to all architectures.

Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
 arch/x86/kvm/mmu/mmu.c   | 24 ++----------------------
 include/linux/kvm_host.h | 26 ++++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 22 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 95beb50748fc..2a0cfa225c8d 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4323,28 +4323,8 @@ static u8 kvm_max_private_mapping_level(struct kvm *kvm, kvm_pfn_t pfn,
 static void kvm_mmu_finish_page_fault(struct kvm_vcpu *vcpu,
 				      struct kvm_page_fault *fault, int r)
 {
-	lockdep_assert_once(lockdep_is_held(&vcpu->kvm->mmu_lock) ||
-			    r == RET_PF_RETRY);
-
-	if (!fault->refcounted_page)
-		return;
-
-	/*
-	 * If the page that KVM got from the *primary MMU* is writable, and KVM
-	 * installed or reused a SPTE, mark the page/folio dirty.  Note, this
-	 * may mark a folio dirty even if KVM created a read-only SPTE, e.g. if
-	 * the GFN is write-protected.  Folios can't be safely marked dirty
-	 * outside of mmu_lock as doing so could race with writeback on the
-	 * folio.  As a result, KVM can't mark folios dirty in the fast page
-	 * fault handler, and so KVM must (somewhat) speculatively mark the
-	 * folio dirty if KVM could locklessly make the SPTE writable.
-	 */
-	if (r == RET_PF_RETRY)
-		kvm_release_page_unused(fault->refcounted_page);
-	else if (!fault->map_writable)
-		kvm_release_page_clean(fault->refcounted_page);
-	else
-		kvm_release_page_dirty(fault->refcounted_page);
+	kvm_release_faultin_page(vcpu->kvm, fault->refcounted_page,
+				 r == RET_PF_RETRY, fault->map_writable);
 }
 
 static int kvm_mmu_faultin_pfn_private(struct kvm_vcpu *vcpu,
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 9d2a97eb30e4..91341cdc6562 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1216,6 +1216,32 @@ static inline void kvm_release_page_unused(struct page *page)
 void kvm_release_page_clean(struct page *page);
 void kvm_release_page_dirty(struct page *page);
 
+static inline void kvm_release_faultin_page(struct kvm *kvm, struct page *page,
+					    bool unused, bool dirty)
+{
+	lockdep_assert_once(lockdep_is_held(&kvm->mmu_lock) || unused);
+
+	if (!page)
+		return;
+
+	/*
+	 * If the page that KVM got from the *primary MMU* is writable, and KVM
+	 * installed or reused a SPTE, mark the page/folio dirty.  Note, this
+	 * may mark a folio dirty even if KVM created a read-only SPTE, e.g. if
+	 * the GFN is write-protected.  Folios can't be safely marked dirty
+	 * outside of mmu_lock as doing so could race with writeback on the
+	 * folio.  As a result, KVM can't mark folios dirty in the fast page
+	 * fault handler, and so KVM must (somewhat) speculatively mark the
+	 * folio dirty if KVM could locklessly make the SPTE writable.
+	 */
+	if (unused)
+		kvm_release_page_unused(page);
+	else if (dirty)
+		kvm_release_page_dirty(page);
+	else
+		kvm_release_page_clean(page);
+}
+
 kvm_pfn_t kvm_lookup_pfn(struct kvm *kvm, gfn_t gfn);
 kvm_pfn_t __kvm_faultin_pfn(const struct kvm_memory_slot *slot, gfn_t gfn,
 			    unsigned int foll, bool *writable,
-- 
2.46.0.rc1.232.g9752f9e123-goog