[RFC PATCH 17/28] arm64: RME: Runtime faulting of memory

[Steven Price]

At runtime if the realm guest accesses memory which hasn't yet been
mapped then KVM needs to either populate the region or fault the guest.

For memory in the lower (protected) region of IPA a fresh page is
provided to the RMM which will zero the contents. For memory in the
upper (shared) region of IPA, the memory from the memslot is mapped
into the realm VM non secure.

Signed-off-by: Steven Price <steven.price@xxxxxxx>
---
 arch/arm64/include/asm/kvm_emulate.h | 10 +++++
 arch/arm64/include/asm/kvm_rme.h     | 12 ++++++
 arch/arm64/kvm/mmu.c                 | 64 +++++++++++++++++++++++++---
 arch/arm64/kvm/rme.c                 | 48 +++++++++++++++++++++
 4 files changed, 128 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 285e62914ca4..3a71b3d2e10a 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -502,6 +502,16 @@ static inline enum realm_state kvm_realm_state(struct kvm *kvm)
 	return READ_ONCE(kvm->arch.realm.state);
 }
 
+static inline gpa_t kvm_gpa_stolen_bits(struct kvm *kvm)
+{
+	if (kvm_is_realm(kvm)) {
+		struct realm *realm = &kvm->arch.realm;
+
+		return BIT(realm->ia_bits - 1);
+	}
+	return 0;
+}
+
 static inline bool vcpu_is_rec(struct kvm_vcpu *vcpu)
 {
 	if (static_branch_unlikely(&kvm_rme_is_available))
diff --git a/arch/arm64/include/asm/kvm_rme.h b/arch/arm64/include/asm/kvm_rme.h
index 9d1583c44a99..303e4a5e5704 100644
--- a/arch/arm64/include/asm/kvm_rme.h
+++ b/arch/arm64/include/asm/kvm_rme.h
@@ -50,6 +50,18 @@ void kvm_destroy_rec(struct kvm_vcpu *vcpu);
 int kvm_rec_enter(struct kvm_vcpu *vcpu);
 int handle_rme_exit(struct kvm_vcpu *vcpu, int rec_run_status);
 
+void kvm_realm_unmap_range(struct kvm *kvm, unsigned long ipa, u64 size);
+int realm_map_protected(struct realm *realm,
+			unsigned long hva,
+			unsigned long base_ipa,
+			struct page *dst_page,
+			unsigned long map_size,
+			struct kvm_mmu_memory_cache *memcache);
+int realm_map_non_secure(struct realm *realm,
+			 unsigned long ipa,
+			 struct page *page,
+			 unsigned long map_size,
+			 struct kvm_mmu_memory_cache *memcache);
 int realm_set_ipa_state(struct kvm_vcpu *vcpu,
 			unsigned long addr, unsigned long end,
 			unsigned long ripas);
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index f29558c5dcbc..5417c273861b 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -235,8 +235,13 @@ static void __unmap_stage2_range(struct kvm_s2_mmu *mmu, phys_addr_t start, u64
 
 	lockdep_assert_held_write(&kvm->mmu_lock);
 	WARN_ON(size & ~PAGE_MASK);
-	WARN_ON(stage2_apply_range(kvm, start, end, kvm_pgtable_stage2_unmap,
-				   may_block));
+
+	if (kvm_is_realm(kvm))
+		kvm_realm_unmap_range(kvm, start, size);
+	else
+		WARN_ON(stage2_apply_range(kvm, start, end,
+					   kvm_pgtable_stage2_unmap,
+					   may_block));
 }
 
 static void unmap_stage2_range(struct kvm_s2_mmu *mmu, phys_addr_t start, u64 size)
@@ -250,7 +255,11 @@ static void stage2_flush_memslot(struct kvm *kvm,
 	phys_addr_t addr = memslot->base_gfn << PAGE_SHIFT;
 	phys_addr_t end = addr + PAGE_SIZE * memslot->npages;
 
-	stage2_apply_range_resched(kvm, addr, end, kvm_pgtable_stage2_flush);
+	if (kvm_is_realm(kvm))
+		kvm_realm_unmap_range(kvm, addr, end - addr);
+	else
+		stage2_apply_range_resched(kvm, addr, end,
+					   kvm_pgtable_stage2_flush);
 }
 
 /**
@@ -818,6 +827,10 @@ void stage2_unmap_vm(struct kvm *kvm)
 	struct kvm_memory_slot *memslot;
 	int idx, bkt;
 
+	/* For realms this is handled by the RMM so nothing to do here */
+	if (kvm_is_realm(kvm))
+		return;
+
 	idx = srcu_read_lock(&kvm->srcu);
 	mmap_read_lock(current->mm);
 	write_lock(&kvm->mmu_lock);
@@ -840,6 +853,7 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu)
 	pgt = mmu->pgt;
 	if (kvm_is_realm(kvm) &&
 	    kvm_realm_state(kvm) != REALM_STATE_DYING) {
+		unmap_stage2_range(mmu, 0, (~0ULL) & PAGE_MASK);
 		write_unlock(&kvm->mmu_lock);
 		kvm_realm_destroy_rtts(&kvm->arch.realm, pgt->ia_bits,
 				       pgt->start_level);
@@ -1190,6 +1204,24 @@ static bool kvm_vma_mte_allowed(struct vm_area_struct *vma)
 	return vma->vm_flags & VM_MTE_ALLOWED;
 }
 
+static int realm_map_ipa(struct kvm *kvm, phys_addr_t ipa, unsigned long hva,
+			 kvm_pfn_t pfn, unsigned long map_size,
+			 enum kvm_pgtable_prot prot,
+			 struct kvm_mmu_memory_cache *memcache)
+{
+	struct realm *realm = &kvm->arch.realm;
+	struct page *page = pfn_to_page(pfn);
+
+	if (WARN_ON(!(prot & KVM_PGTABLE_PROT_W)))
+		return -EFAULT;
+
+	if (!realm_is_addr_protected(realm, ipa))
+		return realm_map_non_secure(realm, ipa, page, map_size,
+					    memcache);
+
+	return realm_map_protected(realm, hva, ipa, page, map_size, memcache);
+}
+
 static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 			  struct kvm_memory_slot *memslot, unsigned long hva,
 			  unsigned long fault_status)
@@ -1210,9 +1242,15 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	unsigned long vma_pagesize, fault_granule;
 	enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R;
 	struct kvm_pgtable *pgt;
+	gpa_t gpa_stolen_mask = kvm_gpa_stolen_bits(vcpu->kvm);
 
 	fault_granule = 1UL << ARM64_HW_PGTABLE_LEVEL_SHIFT(fault_level);
 	write_fault = kvm_is_write_fault(vcpu);
+
+	/* Realms cannot map read-only */
+	if (vcpu_is_rec(vcpu))
+		write_fault = true;
+
 	exec_fault = kvm_vcpu_trap_is_exec_fault(vcpu);
 	VM_BUG_ON(write_fault && exec_fault);
 
@@ -1272,7 +1310,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	if (vma_pagesize == PMD_SIZE || vma_pagesize == PUD_SIZE)
 		fault_ipa &= ~(vma_pagesize - 1);
 
-	gfn = fault_ipa >> PAGE_SHIFT;
+	gfn = (fault_ipa & ~gpa_stolen_mask) >> PAGE_SHIFT;
 	mmap_read_unlock(current->mm);
 
 	/*
@@ -1345,7 +1383,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	 * If we are not forced to use page mapping, check if we are
 	 * backed by a THP and thus use block mapping if possible.
 	 */
-	if (vma_pagesize == PAGE_SIZE && !(force_pte || device)) {
+	/* FIXME: We shouldn't need to disable this for realms */
+	if (vma_pagesize == PAGE_SIZE && !(force_pte || device || kvm_is_realm(kvm))) {
 		if (fault_status == FSC_PERM && fault_granule > PAGE_SIZE)
 			vma_pagesize = fault_granule;
 		else
@@ -1382,6 +1421,9 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	 */
 	if (fault_status == FSC_PERM && vma_pagesize == fault_granule)
 		ret = kvm_pgtable_stage2_relax_perms(pgt, fault_ipa, prot);
+	else if (kvm_is_realm(kvm))
+		ret = realm_map_ipa(kvm, fault_ipa, hva, pfn, vma_pagesize,
+				    prot, memcache);
 	else
 		ret = kvm_pgtable_stage2_map(pgt, fault_ipa, vma_pagesize,
 					     __pfn_to_phys(pfn), prot,
@@ -1437,6 +1479,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
 	struct kvm_memory_slot *memslot;
 	unsigned long hva;
 	bool is_iabt, write_fault, writable;
+	gpa_t gpa_stolen_mask = kvm_gpa_stolen_bits(vcpu->kvm);
 	gfn_t gfn;
 	int ret, idx;
 
@@ -1491,7 +1534,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
 
 	idx = srcu_read_lock(&vcpu->kvm->srcu);
 
-	gfn = fault_ipa >> PAGE_SHIFT;
+	gfn = (fault_ipa & ~gpa_stolen_mask) >> PAGE_SHIFT;
 	memslot = gfn_to_memslot(vcpu->kvm, gfn);
 	hva = gfn_to_hva_memslot_prot(memslot, gfn, &writable);
 	write_fault = kvm_is_write_fault(vcpu);
@@ -1536,6 +1579,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
 		 * of the page size.
 		 */
 		fault_ipa |= kvm_vcpu_get_hfar(vcpu) & ((1 << 12) - 1);
+		fault_ipa &= ~gpa_stolen_mask;
 		ret = io_mem_abort(vcpu, fault_ipa);
 		goto out_unlock;
 	}
@@ -1617,6 +1661,10 @@ bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
 	if (!kvm->arch.mmu.pgt)
 		return false;
 
+	/* We don't support aging for Realms */
+	if (kvm_is_realm(kvm))
+		return true;
+
 	WARN_ON(size != PAGE_SIZE && size != PMD_SIZE && size != PUD_SIZE);
 
 	kpte = kvm_pgtable_stage2_mkold(kvm->arch.mmu.pgt,
@@ -1630,6 +1678,10 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
 	if (!kvm->arch.mmu.pgt)
 		return false;
 
+	/* We don't support aging for Realms */
+	if (kvm_is_realm(kvm))
+		return true;
+
 	return kvm_pgtable_stage2_is_young(kvm->arch.mmu.pgt,
 					   range->start << PAGE_SHIFT);
 }
diff --git a/arch/arm64/kvm/rme.c b/arch/arm64/kvm/rme.c
index 3405b43e1421..3d46191798e5 100644
--- a/arch/arm64/kvm/rme.c
+++ b/arch/arm64/kvm/rme.c
@@ -608,6 +608,54 @@ int realm_map_protected(struct realm *realm,
 	return -ENXIO;
 }
 
+int realm_map_non_secure(struct realm *realm,
+			 unsigned long ipa,
+			 struct page *page,
+			 unsigned long map_size,
+			 struct kvm_mmu_memory_cache *memcache)
+{
+	phys_addr_t rd = virt_to_phys(realm->rd);
+	int map_level;
+	int ret = 0;
+	unsigned long desc = page_to_phys(page) |
+			     PTE_S2_MEMATTR(MT_S2_FWB_NORMAL) |
+			     /* FIXME: Read+Write permissions for now */
+			     (3 << 6) |
+			     PTE_SHARED;
+
+	if (WARN_ON(!IS_ALIGNED(ipa, map_size)))
+		return -EINVAL;
+
+	switch (map_size) {
+	case PAGE_SIZE:
+		map_level = 3;
+		break;
+	case RME_L2_BLOCK_SIZE:
+		map_level = 2;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	ret = rmi_rtt_map_unprotected(rd, ipa, map_level, desc);
+
+	if (RMI_RETURN_STATUS(ret) == RMI_ERROR_RTT) {
+		/* Create missing RTTs and retry */
+		int level = RMI_RETURN_INDEX(ret);
+
+		ret = realm_create_rtt_levels(realm, ipa, level, map_level,
+					      memcache);
+		if (WARN_ON(ret))
+			return -ENXIO;
+
+		ret = rmi_rtt_map_unprotected(rd, ipa, map_level, desc);
+	}
+	if (WARN_ON(ret))
+		return -ENXIO;
+
+	return 0;
+}
+
 static int populate_par_region(struct kvm *kvm,
 			       phys_addr_t ipa_base,
 			       phys_addr_t ipa_end)
-- 
2.34.1