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

Sean Christopherson
2024-07-27T00:19:17Z

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@google.com>
---
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,