KVM: arm64: Use helpers to classify exception types reported via ESR

Currently, we rely on the fact that exceptions can be trivially
classified by applying a mask/value pair to the syndrome value reported
via the ESR register, but this will no longer be true once we enable
support for 5 level paging.

So introduce a couple of helpers that encapsulate this mask/value pair
matching, and wire them up in the code. No functional change intended,
the actual handling of translation level -1 will be added in a
subsequent patch.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
[maz: folded in changes suggested by Mark]
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20231128140400.3132145-2-ardb@google.com

arch/arm64/include/asm/esr.h

@@ -392,6 +392,21 @@ static inline bool esr_is_data_abort(unsigned long esr)
 	return ec == ESR_ELx_EC_DABT_LOW || ec == ESR_ELx_EC_DABT_CUR;
 }
 
+static inline bool esr_fsc_is_translation_fault(unsigned long esr)
+{
+	return (esr & ESR_ELx_FSC_TYPE) == ESR_ELx_FSC_FAULT;
+}
+
+static inline bool esr_fsc_is_permission_fault(unsigned long esr)
+{
+	return (esr & ESR_ELx_FSC_TYPE) == ESR_ELx_FSC_PERM;
+}
+
+static inline bool esr_fsc_is_access_flag_fault(unsigned long esr)
+{
+	return (esr & ESR_ELx_FSC_TYPE) == ESR_ELx_FSC_ACCESS;
+}
+
 const char *esr_get_class_string(unsigned long esr);
 #endif /* __ASSEMBLY */
 

arch/arm64/include/asm/kvm_emulate.h

@@ -404,24 +404,25 @@ static __always_inline u8 kvm_vcpu_trap_get_fault(const struct kvm_vcpu *vcpu)
 	return kvm_vcpu_get_esr(vcpu) & ESR_ELx_FSC;
 }
 
-static __always_inline u8 kvm_vcpu_trap_get_fault_type(const struct kvm_vcpu *vcpu)
+static inline
+bool kvm_vcpu_trap_is_permission_fault(const struct kvm_vcpu *vcpu)
 {
-	return kvm_vcpu_get_esr(vcpu) & ESR_ELx_FSC_TYPE;
+	return esr_fsc_is_permission_fault(kvm_vcpu_get_esr(vcpu));
 }
 
-static __always_inline s8 kvm_vcpu_trap_get_fault_level(const struct kvm_vcpu *vcpu)
+static inline
+bool kvm_vcpu_trap_is_translation_fault(const struct kvm_vcpu *vcpu)
 {
-	/*
-	 * Note: With the introduction of FEAT_LPA2 an extra level of
-	 * translation (level -1) is added. This level (obviously) doesn't
-	 * follow the previous convention of encoding the 4 levels in the 2 LSBs
-	 * of the FSC so this function breaks if the fault is for level -1.
-	 *
-	 * However, stage2 tables always use concatenated tables for first level
-	 * lookup and therefore it is guaranteed that the level will be between
-	 * 0 and 3, and this function continues to work.
-	 */
-	return kvm_vcpu_get_esr(vcpu) & ESR_ELx_FSC_LEVEL;
+	return esr_fsc_is_translation_fault(kvm_vcpu_get_esr(vcpu));
+}
+
+static inline
+u64 kvm_vcpu_trap_get_perm_fault_granule(const struct kvm_vcpu *vcpu)
+{
+	unsigned long esr = kvm_vcpu_get_esr(vcpu);
+
+	BUG_ON(!esr_fsc_is_permission_fault(esr));
+	return BIT(ARM64_HW_PGTABLE_LEVEL_SHIFT(esr & ESR_ELx_FSC_LEVEL));
 }
 
 static __always_inline bool kvm_vcpu_abt_issea(const struct kvm_vcpu *vcpu)
@@ -464,12 +465,7 @@ static inline bool kvm_is_write_fault(struct kvm_vcpu *vcpu)
 		 * first), then a permission fault to allow the flags
 		 * to be set.
 		 */
-		switch (kvm_vcpu_trap_get_fault_type(vcpu)) {
-		case ESR_ELx_FSC_PERM:
-			return true;
-		default:
-			return false;
-		}
+		return kvm_vcpu_trap_is_permission_fault(vcpu);
 	}
 
 	if (kvm_vcpu_trap_is_iabt(vcpu))

arch/arm64/kvm/hyp/include/hyp/fault.h

@@ -60,7 +60,7 @@ static inline bool __get_fault_info(u64 esr, struct kvm_vcpu_fault_info *fault)
 	 */
 	if (!(esr & ESR_ELx_S1PTW) &&
 	    (cpus_have_final_cap(ARM64_WORKAROUND_834220) ||
-	     (esr & ESR_ELx_FSC_TYPE) == ESR_ELx_FSC_PERM)) {
+	     esr_fsc_is_permission_fault(esr))) {
 		if (!__translate_far_to_hpfar(far, &hpfar))
 			return false;
 	} else {

arch/arm64/kvm/hyp/include/hyp/switch.h

@@ -591,7 +591,7 @@ static bool kvm_hyp_handle_dabt_low(struct kvm_vcpu *vcpu, u64 *exit_code)
 	if (static_branch_unlikely(&vgic_v2_cpuif_trap)) {
 		bool valid;
 
-		valid = kvm_vcpu_trap_get_fault_type(vcpu) == ESR_ELx_FSC_FAULT &&
+		valid = kvm_vcpu_trap_is_translation_fault(vcpu) &&
 			kvm_vcpu_dabt_isvalid(vcpu) &&
 			!kvm_vcpu_abt_issea(vcpu) &&
 			!kvm_vcpu_abt_iss1tw(vcpu);

arch/arm64/kvm/mmu.c

@@ -1376,7 +1376,7 @@ static bool kvm_vma_mte_allowed(struct vm_area_struct *vma)
 
 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)
+			  bool fault_is_perm)
 {
 	int ret = 0;
 	bool write_fault, writable, force_pte = false;
@@ -1390,17 +1390,17 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	gfn_t gfn;
 	kvm_pfn_t pfn;
 	bool logging_active = memslot_is_logging(memslot);
-	s8 fault_level = kvm_vcpu_trap_get_fault_level(vcpu);
 	long vma_pagesize, fault_granule;
 	enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R;
 	struct kvm_pgtable *pgt;
 
-	fault_granule = 1UL << ARM64_HW_PGTABLE_LEVEL_SHIFT(fault_level);
+	if (fault_is_perm)
+		fault_granule = kvm_vcpu_trap_get_perm_fault_granule(vcpu);
 	write_fault = kvm_is_write_fault(vcpu);
 	exec_fault = kvm_vcpu_trap_is_exec_fault(vcpu);
 	VM_BUG_ON(write_fault && exec_fault);
 
-	if (fault_status == ESR_ELx_FSC_PERM && !write_fault && !exec_fault) {
+	if (fault_is_perm && !write_fault && !exec_fault) {
 		kvm_err("Unexpected L2 read permission error\n");
 		return -EFAULT;
 	}
@@ -1411,8 +1411,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	 * only exception to this is when dirty logging is enabled at runtime
 	 * and a write fault needs to collapse a block entry into a table.
 	 */
-	if (fault_status != ESR_ELx_FSC_PERM ||
-	    (logging_active && write_fault)) {
+	if (!fault_is_perm || (logging_active && write_fault)) {
 		ret = kvm_mmu_topup_memory_cache(memcache,
 						 kvm_mmu_cache_min_pages(vcpu->arch.hw_mmu));
 		if (ret)
@@ -1529,8 +1528,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	 * backed by a THP and thus use block mapping if possible.
 	 */
 	if (vma_pagesize == PAGE_SIZE && !(force_pte || device)) {
-		if (fault_status ==  ESR_ELx_FSC_PERM &&
-		    fault_granule > PAGE_SIZE)
+		if (fault_is_perm && fault_granule > PAGE_SIZE)
 			vma_pagesize = fault_granule;
 		else
 			vma_pagesize = transparent_hugepage_adjust(kvm, memslot,
@@ -1543,7 +1541,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 		}
 	}
 
-	if (fault_status != ESR_ELx_FSC_PERM && !device && kvm_has_mte(kvm)) {
+	if (!fault_is_perm && !device && kvm_has_mte(kvm)) {
 		/* Check the VMM hasn't introduced a new disallowed VMA */
 		if (mte_allowed) {
 			sanitise_mte_tags(kvm, pfn, vma_pagesize);
@@ -1569,7 +1567,7 @@ 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_status == ESR_ELx_FSC_PERM && vma_pagesize == fault_granule)
+	if (fault_is_perm && vma_pagesize == fault_granule)
 		ret = kvm_pgtable_stage2_relax_perms(pgt, fault_ipa, prot);
 	else
 		ret = kvm_pgtable_stage2_map(pgt, fault_ipa, vma_pagesize,
@@ -1620,7 +1618,7 @@ static void handle_access_fault(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa)
  */
 int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
 {
-	unsigned long fault_status;
+	unsigned long esr;
 	phys_addr_t fault_ipa;
 	struct kvm_memory_slot *memslot;
 	unsigned long hva;
@@ -1628,12 +1626,12 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
 	gfn_t gfn;
 	int ret, idx;
 
-	fault_status = kvm_vcpu_trap_get_fault_type(vcpu);
+	esr = kvm_vcpu_get_esr(vcpu);
 
 	fault_ipa = kvm_vcpu_get_fault_ipa(vcpu);
 	is_iabt = kvm_vcpu_trap_is_iabt(vcpu);
 
-	if (fault_status == ESR_ELx_FSC_FAULT) {
+	if (esr_fsc_is_permission_fault(esr)) {
 		/* Beyond sanitised PARange (which is the IPA limit) */
 		if (fault_ipa >= BIT_ULL(get_kvm_ipa_limit())) {
 			kvm_inject_size_fault(vcpu);
@@ -1668,9 +1666,9 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
 			      kvm_vcpu_get_hfar(vcpu), fault_ipa);
 
 	/* Check the stage-2 fault is trans. fault or write fault */
-	if (fault_status != ESR_ELx_FSC_FAULT &&
-	    fault_status != ESR_ELx_FSC_PERM &&
-	    fault_status != ESR_ELx_FSC_ACCESS) {
+	if (!esr_fsc_is_translation_fault(esr) &&
+	    !esr_fsc_is_permission_fault(esr) &&
+	    !esr_fsc_is_access_flag_fault(esr)) {
 		kvm_err("Unsupported FSC: EC=%#x xFSC=%#lx ESR_EL2=%#lx\n",
 			kvm_vcpu_trap_get_class(vcpu),
 			(unsigned long)kvm_vcpu_trap_get_fault(vcpu),
@@ -1732,13 +1730,14 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
 	/* Userspace should not be able to register out-of-bounds IPAs */
 	VM_BUG_ON(fault_ipa >= kvm_phys_size(vcpu->arch.hw_mmu));
 
-	if (fault_status == ESR_ELx_FSC_ACCESS) {
+	if (esr_fsc_is_access_flag_fault(esr)) {
 		handle_access_fault(vcpu, fault_ipa);
 		ret = 1;
 		goto out_unlock;
 	}
 
-	ret = user_mem_abort(vcpu, fault_ipa, memslot, hva, fault_status);
+	ret = user_mem_abort(vcpu, fault_ipa, memslot, hva,
+			     esr_fsc_is_permission_fault(esr));
 	if (ret == 0)
 		ret = 1;
 out: