[PATCH 03/12] KVM: arm64: Report hardware dirty status of stage2 PTE if coverred

[Keqian Zhu]

kvm_set_pte is called to replace a target PTE with a desired one.
We always do this without changing the desired one, but if dirty
status set by hardware is coverred, let caller know it.

Signed-off-by: Keqian Zhu <zhukeqian1@xxxxxxxxxx>
---
 arch/arm64/kvm/mmu.c | 36 +++++++++++++++++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 5ad87bce23c0..27407153121b 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -194,11 +194,45 @@ static void clear_stage2_pmd_entry(struct kvm *kvm, pmd_t *pmd, phys_addr_t addr
 	put_page(virt_to_page(pmd));
 }
 
-static inline void kvm_set_pte(pte_t *ptep, pte_t new_pte)
+#ifdef CONFIG_ARM64_HW_AFDBM
+/**
+ * @ret: true if dirty status set by hardware is coverred.
+ */
+static bool kvm_set_pte(pte_t *ptep, pte_t new_pte)
+{
+	pteval_t old_pteval, new_pteval, pteval;
+	bool old_logging, new_no_write;
+
+	old_logging = kvm_hw_dbm_enabled() && !pte_none(*ptep) &&
+		      kvm_s2pte_dbm(ptep);
+	new_no_write = pte_none(new_pte) || kvm_s2pte_readonly(&new_pte);
+
+	if (!old_logging || !new_no_write) {
+		WRITE_ONCE(*ptep, new_pte);
+		dsb(ishst);
+		return false;
+	}
+
+	new_pteval = pte_val(new_pte);
+	pteval = READ_ONCE(pte_val(*ptep));
+	do {
+		old_pteval = pteval;
+		pteval = cmpxchg_relaxed(&pte_val(*ptep), old_pteval, new_pteval);
+	} while (pteval != old_pteval);
+
+	return !kvm_s2pte_readonly(&__pte(pteval));
+}
+#else
+/**
+ * @ret: true if dirty status set by hardware is coverred.
+ */
+static inline bool kvm_set_pte(pte_t *ptep, pte_t new_pte)
 {
 	WRITE_ONCE(*ptep, new_pte);
 	dsb(ishst);
+	return false;
 }
+#endif /* CONFIG_ARM64_HW_AFDBM */
 
 static inline void kvm_set_pmd(pmd_t *pmdp, pmd_t new_pmd)
 {
-- 
2.19.1