[PATCH v4 55/66] KVM: arm64: Allow populating S2 SW bits

[Marc Zyngier]

The S2 page table code doesn't use the SW bits yet, but we are about
to need them to encode some guest Stage-2 information (its mapping size
in the form of the TTL encoding).

Propagate the SW bits specified by the caller, and store them into
the corresponding entry.

Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/include/asm/kvm_pgtable.h | 10 ++++++++++
 arch/arm64/kvm/hyp/pgtable.c         |  6 ++++++
 2 files changed, 16 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index c3674c47d48c..4f432ea3094c 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -92,6 +92,10 @@ struct kvm_pgtable {
  * @KVM_PGTABLE_PROT_W:		Write permission.
  * @KVM_PGTABLE_PROT_R:		Read permission.
  * @KVM_PGTABLE_PROT_DEVICE:	Device attributes.
+ * @KVM_PGTABLE_PROT_S2_SW0:	SW bit 0.
+ * @KVM_PGTABLE_PROT_S2_SW1:	SW bit 1.
+ * @KVM_PGTABLE_PROT_S2_SW2:	SW bit 2.
+ * @KVM_PGTABLE_PROT_S2_SW3:	SW bit 3.
  */
 enum kvm_pgtable_prot {
 	KVM_PGTABLE_PROT_X			= BIT(0),
@@ -99,6 +103,12 @@ enum kvm_pgtable_prot {
 	KVM_PGTABLE_PROT_R			= BIT(2),
 
 	KVM_PGTABLE_PROT_DEVICE			= BIT(3),
+
+	/* Cunningly, this matches the PTE bits... */
+	KVM_PGTABLE_PROT_S2_SW0			= BIT(55),
+	KVM_PGTABLE_PROT_S2_SW1			= BIT(56),
+	KVM_PGTABLE_PROT_S2_SW2			= BIT(57),
+	KVM_PGTABLE_PROT_S2_SW3			= BIT(58),
 };
 
 #define PAGE_HYP		(KVM_PGTABLE_PROT_R | KVM_PGTABLE_PROT_W)
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index c37c1dc4feaf..fa85da30c9b8 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -43,6 +43,7 @@
 #define KVM_PTE_LEAF_ATTR_HI_S1_XN	BIT(54)
 
 #define KVM_PTE_LEAF_ATTR_HI_S2_XN	BIT(54)
+#define KVM_PTE_LEAF_ATTR_HI_S2_SW	GENMASK(58, 55)
 
 #define KVM_PTE_LEAF_ATTR_S2_PERMS	(KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R | \
 					 KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | \
@@ -539,6 +540,7 @@ static int stage2_set_prot_attr(struct kvm_pgtable *pgt, enum kvm_pgtable_prot p
 
 	attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S2_SH, sh);
 	attr |= KVM_PTE_LEAF_ATTR_LO_S2_AF;
+	attr |= prot & KVM_PTE_LEAF_ATTR_HI_S2_SW;
 	*ptep = attr;
 
 	return 0;
@@ -975,6 +977,10 @@ int kvm_pgtable_stage2_relax_perms(struct kvm_pgtable *pgt, u64 addr,
 	if (prot & KVM_PGTABLE_PROT_X)
 		clr |= KVM_PTE_LEAF_ATTR_HI_S2_XN;
 
+	/* Always propagate the SW bits */
+	clr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_HI_S2_SW, 0xf);
+	set |= prot & KVM_PTE_LEAF_ATTR_HI_S2_SW;
+
 	ret = stage2_update_leaf_attrs(pgt, addr, 1, set, clr, NULL, &level);
 	if (!ret)
 		kvm_call_hyp(__kvm_tlb_flush_vmid_ipa, pgt->mmu, addr, level);
-- 
2.29.2