Subject: [PATCH v5 05/69] KVM: arm64: Allow preservation of the S2 SW bits

From: Marc Zyngier <[email-masked]>
Date: Mon, 29 Nov 2021 20:00:46 +0000

The S2 page table code has a limited use the SW bits, 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 <[email-masked]>
---
 arch/arm64/kvm/hyp/pgtable.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 8cdbc43fa651..d69e400b2de6 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -1064,9 +1064,6 @@ int kvm_pgtable_stage2_relax_perms(struct kvm_pgtable *pgt, u64 addr,
 	u32 level;
 	kvm_pte_t set = 0, clr = 0;
 
-	if (prot & KVM_PTE_LEAF_ATTR_HI_SW)
-		return -EINVAL;
-
 	if (prot & KVM_PGTABLE_PROT_R)
 		set |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R;
 
@@ -1076,6 +1073,10 @@ 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_SW, 0xf);
+	set |= prot & KVM_PTE_LEAF_ATTR_HI_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);
-- 
2.30.2

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