[PATCH v11 13/18] KVM: arm64: Refactor user_mem_abort()

[Fuad Tabba <tabba@google.com>]

To simplify the code and to make the assumptions clearer,
refactor user_mem_abort() by immediately setting force_pte to
true if the conditions are met.

Remove the comment about logging_active being guaranteed to never be
true for VM_PFNMAP memslots, since it's not actually correct.

Move code that will be reused in the following patch into separate
functions.

Other small instances of tidying up.

No functional change intended.

Signed-off-by: Fuad Tabba <tabba@google.com>
---
 arch/arm64/kvm/mmu.c | 100 ++++++++++++++++++++++++-------------------
 1 file changed, 55 insertions(+), 45 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index eeda92330ade..ce80be116a30 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1466,13 +1466,56 @@ static bool kvm_vma_mte_allowed(struct vm_area_struct *vma)
 	return vma->vm_flags & VM_MTE_ALLOWED;
 }
 
+static int prepare_mmu_memcache(struct kvm_vcpu *vcpu, bool topup_memcache,
+				void **memcache)
+{
+	int min_pages;
+
+	if (!is_protected_kvm_enabled())
+		*memcache = &vcpu->arch.mmu_page_cache;
+	else
+		*memcache = &vcpu->arch.pkvm_memcache;
+
+	if (!topup_memcache)
+		return 0;
+
+	min_pages = kvm_mmu_cache_min_pages(vcpu->arch.hw_mmu);
+
+	if (!is_protected_kvm_enabled())
+		return kvm_mmu_topup_memory_cache(*memcache, min_pages);
+
+	return topup_hyp_memcache(*memcache, min_pages);
+}
+
+/*
+ * 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 original translation in the SW bits of the leaf
+ * entry as a proxy for the span of that translation. This will be retrieved on
+ * TLB invalidation from the guest and used to limit the invalidation scope if a
+ * TTL hint or a range isn't provided.
+ */
+static void adjust_nested_fault_perms(struct kvm_s2_trans *nested,
+				      enum kvm_pgtable_prot *prot,
+				      bool *writable)
+{
+	*writable &= kvm_s2_trans_writable(nested);
+	if (!kvm_s2_trans_readable(nested))
+		*prot &= ~KVM_PGTABLE_PROT_R;
+
+	*prot |= kvm_encode_nested_level(nested);
+}
+
 static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 			  struct kvm_s2_trans *nested,
 			  struct kvm_memory_slot *memslot, unsigned long hva,
 			  bool fault_is_perm)
 {
 	int ret = 0;
-	bool write_fault, writable, force_pte = false;
+	bool topup_memcache;
+	bool write_fault, writable;
 	bool exec_fault, mte_allowed;
 	bool device = false, vfio_allow_any_uc = false;
 	unsigned long mmu_seq;
@@ -1484,6 +1527,7 @@ 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);
+	bool force_pte = logging_active || is_protected_kvm_enabled();
 	long vma_pagesize, fault_granule;
 	enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R;
 	struct kvm_pgtable *pgt;
@@ -1501,28 +1545,16 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 		return -EFAULT;
 	}
 
-	if (!is_protected_kvm_enabled())
-		memcache = &vcpu->arch.mmu_page_cache;
-	else
-		memcache = &vcpu->arch.pkvm_memcache;
-
 	/*
 	 * Permission faults just need to update the existing leaf entry,
 	 * and so normally don't require allocations from the memcache. The
 	 * 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_is_perm || (logging_active && write_fault)) {
-		int min_pages = kvm_mmu_cache_min_pages(vcpu->arch.hw_mmu);
-
-		if (!is_protected_kvm_enabled())
-			ret = kvm_mmu_topup_memory_cache(memcache, min_pages);
-		else
-			ret = topup_hyp_memcache(memcache, min_pages);
-
-		if (ret)
-			return ret;
-	}
+	topup_memcache = !fault_is_perm || (logging_active && write_fault);
+	ret = prepare_mmu_memcache(vcpu, topup_memcache, &memcache);
+	if (ret)
+		return ret;
 
 	/*
 	 * Let's check if we will get back a huge page backed by hugetlbfs, or
@@ -1536,16 +1568,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 		return -EFAULT;
 	}
 
-	/*
-	 * logging_active is guaranteed to never be true for VM_PFNMAP
-	 * memslots.
-	 */
-	if (logging_active || is_protected_kvm_enabled()) {
-		force_pte = true;
+	if (force_pte)
 		vma_shift = PAGE_SHIFT;
-	} else {
+	else
 		vma_shift = get_vma_page_shift(vma, hva);
-	}
 
 	switch (vma_shift) {
 #ifndef __PAGETABLE_PMD_FOLDED
@@ -1597,7 +1623,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 			max_map_size = PAGE_SIZE;
 
 		force_pte = (max_map_size == PAGE_SIZE);
-		vma_pagesize = min(vma_pagesize, (long)max_map_size);
+		vma_pagesize = min_t(long, vma_pagesize, max_map_size);
 	}
 
 	/*
@@ -1626,7 +1652,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	 * Rely on mmap_read_unlock() for an implicit smp_rmb(), which pairs
 	 * with the smp_wmb() in kvm_mmu_invalidate_end().
 	 */
-	mmu_seq = vcpu->kvm->mmu_invalidate_seq;
+	mmu_seq = kvm->mmu_invalidate_seq;
 	mmap_read_unlock(current->mm);
 
 	pfn = __kvm_faultin_pfn(memslot, gfn, write_fault ? FOLL_WRITE : 0,
@@ -1661,24 +1687,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	if (exec_fault && device)
 		return -ENOEXEC;
 
-	/*
-	 * 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 original translation in the SW bits
-	 * of the leaf entry as a proxy for the span of that translation.
-	 * This will be retrieved on TLB invalidation from the guest and
-	 * used to limit the invalidation scope if a TTL hint or a range
-	 * isn't provided.
-	 */
-	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);
-	}
+	if (nested)
+		adjust_nested_fault_perms(nested, &prot, &writable);
 
 	kvm_fault_lock(kvm);
 	pgt = vcpu->arch.hw_mmu->pgt;
-- 
2.49.0.1266.g31b7d2e469-goog