[PATCH 13/22] KVM: arm64: Set dirty state at stage-1

[Oliver Upton <oupton@kernel.org>]

Mark the descriptor as dirty if the permissions are sufficient to grant
write access. Note that compute_s1_direct_permissions() already
considers the DBM bit as writable.

Signed-off-by: Oliver Upton <oupton@kernel.org>
---

Spotted right before posting:

TCR_ELx.HD is conditioned on TCR_ELx.HA being set, which is missing from
this patch. I'll address in v2.

 arch/arm64/include/asm/kvm_arm.h    |  1 +
 arch/arm64/include/asm/kvm_nested.h |  1 +
 arch/arm64/kvm/at.c                 | 23 +++++++++++++++++++++++
 3 files changed, 25 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index 3f9233b5a130..3f7fa9c3e9c5 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -111,6 +111,7 @@
 #define TCR_EL2_DS		(1UL << 32)
 #define TCR_EL2_RES1		((1U << 31) | (1 << 23))
 #define TCR_EL2_HPD		(1 << 24)
+#define TCR_EL2_HD		(1 << 22)
 #define TCR_EL2_HA		(1 << 21)
 #define TCR_EL2_TBI		(1 << 20)
 #define TCR_EL2_PS_SHIFT	16
diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
index 347d79fd350c..1bb070328b1c 100644
--- a/arch/arm64/include/asm/kvm_nested.h
+++ b/arch/arm64/include/asm/kvm_nested.h
@@ -316,6 +316,7 @@ struct s1_walk_info {
 	bool	     		s2;
 	bool			pa52bit;
 	bool			ha;
+	bool			hd;
 };
 
 struct s1_walk_result {
diff --git a/arch/arm64/kvm/at.c b/arch/arm64/kvm/at.c
index 0218176107b5..bfba31b270a9 100644
--- a/arch/arm64/kvm/at.c
+++ b/arch/arm64/kvm/at.c
@@ -412,6 +412,10 @@ static int setup_s1_walk(struct kvm_vcpu *vcpu, struct s1_walk_info *wi,
 	wi->ha &= (wi->regime == TR_EL2 ?
 		  FIELD_GET(TCR_EL2_HA, tcr) :
 		  FIELD_GET(TCR_HA, tcr));
+	wi->hd  = kvm_has_feat(vcpu->kvm, ID_AA64MMFR1_EL1, HAFDBS, DBM);
+	wi->hd &= (wi->regime == TR_EL2 ?
+		  FIELD_GET(TCR_EL2_HD, tcr) :
+		  FIELD_GET(TCR_HD, tcr));
 
 	return 0;
 
@@ -455,6 +459,22 @@ static int kvm_read_s1_desc(struct kvm_vcpu *vcpu, u64 pa, u64 *desc,
 	return 0;
 }
 
+static bool should_set_dirty_state(struct s1_walk_info *wi, struct s1_walk_step *ws,
+				   struct s1_walk_result *wr, struct kvm_walk_access *access)
+{
+	bool perm = wi->as_el0 ? wr->uw : wr->pw;
+
+	switch (access->type) {
+	/* R_RKMHW */
+	case WALK_ACCESS_CMO:
+	case WALK_ACCESS_AT:
+		return false;
+	default:
+		/* R_NSXRD */
+		return access->write && wi->hd && perm;
+	}
+}
+
 static int handle_desc_update(struct kvm_vcpu *vcpu, struct s1_walk_info *wi,
 			      struct s1_walk_step *ws, struct s1_walk_result *wr,
 			      struct kvm_walk_access *access)
@@ -467,6 +487,9 @@ static int handle_desc_update(struct kvm_vcpu *vcpu, struct s1_walk_info *wi,
 	if (wi->ha)
 		new |= PTE_AF;
 
+	if (should_set_dirty_state(wi, ws, wr, access))
+		new &= ~PTE_RDONLY;
+
 	if (new == old)
 		return 0;
 
-- 
2.47.3