[PATCH v3 2/5] KVM: arm64: Add support to set the DBM attr during memory abort

[Tian Zheng]

From: eillon <yezhenyu2 at huawei.com>

This patch adds support to set the DBM (Dirty Bit Modifier) attribute
in S2 PTE during user_mem_abort(). This bit, introduced in ARMv8.1,
enables hardware to automatically promote write-clean pages to write-dirty.
This prevents the guest from being trapped in EL2 due to missing write
permissions.

Signed-off-by: eillon <yezhenyu2 at huawei.com>
Signed-off-by: Tian Zheng <zhengtian10 at huawei.com>
---
 arch/arm64/include/asm/kvm_pgtable.h | 4 ++++
 arch/arm64/kvm/hyp/pgtable.c         | 6 ++++++
 2 files changed, 10 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index c201168f2857..d0f280972a7a 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -93,6 +93,8 @@ typedef u64 kvm_pte_t;

 #define KVM_PTE_LEAF_ATTR_HI_S2_XN	GENMASK(54, 53)

+#define KVM_PTE_LEAF_ATTR_HI_S2_DBM	BIT(51)
+
 #define KVM_PTE_LEAF_ATTR_HI_S1_GP	BIT(50)

 #define KVM_PTE_LEAF_ATTR_S2_PERMS	(KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R | \
@@ -248,6 +250,7 @@ enum kvm_pgtable_stage2_flags {
  * @KVM_PGTABLE_PROT_R:		Read permission.
  * @KVM_PGTABLE_PROT_DEVICE:	Device attributes.
  * @KVM_PGTABLE_PROT_NORMAL_NC:	Normal noncacheable attributes.
+ * @KVM_PGTABLE_PROT_DBM:	Dirty bit management attribute.
  * @KVM_PGTABLE_PROT_SW0:	Software bit 0.
  * @KVM_PGTABLE_PROT_SW1:	Software bit 1.
  * @KVM_PGTABLE_PROT_SW2:	Software bit 2.
@@ -263,6 +266,7 @@ enum kvm_pgtable_prot {

 	KVM_PGTABLE_PROT_DEVICE			= BIT(4),
 	KVM_PGTABLE_PROT_NORMAL_NC		= BIT(5),
+	KVM_PGTABLE_PROT_DBM			= BIT(6),

 	KVM_PGTABLE_PROT_SW0			= BIT(55),
 	KVM_PGTABLE_PROT_SW1			= BIT(56),
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 0e4ddd28ef5d..5b4c46d8dc74 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -739,6 +739,9 @@ static int stage2_set_prot_attr(struct kvm_pgtable *pgt, enum kvm_pgtable_prot p
 	if (prot & KVM_PGTABLE_PROT_W)
 		attr |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W;

+	if (prot & KVM_PGTABLE_PROT_DBM)
+		attr |= KVM_PTE_LEAF_ATTR_HI_S2_DBM;
+
 	if (!kvm_lpa2_is_enabled())
 		attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S2_SH, sh);

@@ -1361,6 +1364,9 @@ int kvm_pgtable_stage2_relax_perms(struct kvm_pgtable *pgt, u64 addr,
 	if (prot & KVM_PGTABLE_PROT_W)
 		set |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W;

+	if (prot & KVM_PGTABLE_PROT_DBM)
+		set |= KVM_PTE_LEAF_ATTR_HI_S2_DBM;
+
 	ret = stage2_set_xn_attr(prot, &xn);
 	if (ret)
 		return ret;
--
2.33.0