[RFC PATCH 1/7] KVM: arm64: Add some basic functions for hw DBM

[Keqian Zhu <zhukeqian1@huawei.com>]

Prepare some basic functions used by following patches to support
hardware DBM.

Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Peng Liang <liangpeng10@huawei.com>
---
 arch/arm64/include/asm/kvm_mmu.h | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 30b0e8d6b895..8df078f0ee67 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -285,6 +285,30 @@ static inline bool kvm_s2pud_young(pud_t pud)
 	return pud_young(pud);
 }
 
+#ifdef CONFIG_ARM64_HW_AFDBM
+static inline bool kvm_hw_dbm_enabled(void)
+{
+	return !!(read_sysreg(vtcr_el2) & VTCR_EL2_HD);
+}
+
+static inline void kvm_set_s2pte_dbm(pte_t *ptep)
+{
+	pteval_t old_pteval, pteval;
+
+	pteval = READ_ONCE(pte_val(*ptep));
+	do {
+		old_pteval = pteval;
+		pteval |= PTE_DBM;
+		pteval = cmpxchg_relaxed(&pte_val(*ptep), old_pteval, pteval);
+	} while (pteval != old_pteval);
+}
+
+static inline bool kvm_s2pte_dbm(pte_t *ptep)
+{
+	return !!(READ_ONCE(pte_val(*ptep)) & PTE_DBM);
+}
+#endif /* CONFIG_ARM64_HW_AFDBM */
+
 #define hyp_pte_table_empty(ptep) kvm_page_empty(ptep)
 
 #ifdef __PAGETABLE_PMD_FOLDED
-- 
2.19.1