[PATCH v2 12/16] KVM: arm64: nv: Tag shadow S2 entries with guest's leaf S2 level

[Marc Zyngier <maz@kernel.org>]

Populate bits [56:55] of the leaf entry with the level provided
by the guest's S2 translation. This will allow us to better scope
the invalidation by remembering the mapping size.

Of course, this assume that the guest will issue an invalidation
with an address that falls into the same leaf. If the guest doesn't,
we'll over-invalidate.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/include/asm/kvm_nested.h |  8 ++++++++
 arch/arm64/kvm/mmu.c                | 17 +++++++++++++++--
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
index fcb0de3a93fe..971dbe533730 100644
--- a/arch/arm64/include/asm/kvm_nested.h
+++ b/arch/arm64/include/asm/kvm_nested.h
@@ -5,6 +5,7 @@
 #include <linux/bitfield.h>
 #include <linux/kvm_host.h>
 #include <asm/kvm_emulate.h>
+#include <asm/kvm_pgtable.h>
 
 static inline bool vcpu_has_nv(const struct kvm_vcpu *vcpu)
 {
@@ -195,4 +196,11 @@ static inline bool kvm_auth_eretax(struct kvm_vcpu *vcpu, u64 *elr)
 }
 #endif
 
+#define KVM_NV_GUEST_MAP_SZ	(KVM_PGTABLE_PROT_SW1 | KVM_PGTABLE_PROT_SW0)
+
+static inline u64 kvm_encode_nested_level(struct kvm_s2_trans *trans)
+{
+	return FIELD_PREP(KVM_NV_GUEST_MAP_SZ, trans->level);
+}
+
 #endif /* __ARM64_KVM_NESTED_H */
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 4ed93a384255..f3a8ec70bd29 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1598,11 +1598,17 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	 * Potentially reduce shadow S2 permissions to match the guest's own
 	 * S2. For exec faults, we'd only reach this point if the guest
 	 * actually allowed it (see kvm_s2_handle_perm_fault).
+	 *
+	 * Also encode the level of the nested translation in the SW bits of
+	 * the PTE/PMD/PUD. This will be retrived on TLB invalidation from
+	 * the guest.
 	 */
 	if (nested) {
 		writable &= kvm_s2_trans_writable(nested);
 		if (!kvm_s2_trans_readable(nested))
 			prot &= ~KVM_PGTABLE_PROT_R;
+
+		prot |= kvm_encode_nested_level(nested);
 	}
 
 	read_lock(&kvm->mmu_lock);
@@ -1661,14 +1667,21 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	 * permissions only if vma_pagesize equals fault_granule. Otherwise,
 	 * kvm_pgtable_stage2_map() should be called to change block size.
 	 */
-	if (fault_is_perm && vma_pagesize == fault_granule)
+	if (fault_is_perm && vma_pagesize == fault_granule) {
+		/*
+		 * Drop the SW bits in favour of those stored in the
+		 * PTE, which will be preserved.
+		 */
+		prot &= ~KVM_NV_GUEST_MAP_SZ;
 		ret = kvm_pgtable_stage2_relax_perms(pgt, fault_ipa, prot);
-	else
+	} else {
 		ret = kvm_pgtable_stage2_map(pgt, fault_ipa, vma_pagesize,
 					     __pfn_to_phys(pfn), prot,
 					     memcache,
 					     KVM_PGTABLE_WALK_HANDLE_FAULT |
 					     KVM_PGTABLE_WALK_SHARED);
+	}
+
 out_unlock:
 	read_unlock(&kvm->mmu_lock);
 
-- 
2.39.2


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