Re: [PATCH v6 20/43] arm64: RME: Runtime faulting of memory

[Aneesh Kumar K.V <aneesh.kumar@kernel.org>]

Gavin Shan <gshan@redhat.com> writes:

> On 12/13/24 1:55 AM, Steven Price wrote:
 
....

>> +static int private_memslot_fault(struct kvm_vcpu *vcpu,
>> +				 phys_addr_t fault_ipa,
>> +				 struct kvm_memory_slot *memslot)
>> +{
>> +	struct kvm *kvm = vcpu->kvm;
>> +	gpa_t gpa = kvm_gpa_from_fault(kvm, fault_ipa);
>> +	gfn_t gfn = gpa >> PAGE_SHIFT;
>> +	bool priv_exists = kvm_mem_is_private(kvm, gfn);
>> +	struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;
>> +	struct page *page;
>> +	kvm_pfn_t pfn;
>> +	int ret;
>> +	/*
>> +	 * For Realms, the shared address is an alias of the private GPA with
>> +	 * the top bit set. Thus is the fault address matches the GPA then it
>> +	 * is the private alias.
>> +	 */
>> +	bool is_priv_gfn = (gpa == fault_ipa);
>> +
>
> We may rename 'priv_exists' to 'was_priv_gfn', which is consistent to 'is_priv_gfn'.
> Alternatively, we may use 'was_private' and 'is_private'.
>
>> +	if (priv_exists != is_priv_gfn) {
>> +		kvm_prepare_memory_fault_exit(vcpu,
>> +					      gpa,
>> +					      PAGE_SIZE,
>> +					      kvm_is_write_fault(vcpu),
>> +					      false, is_priv_gfn);
>> +
>> +		return -EFAULT;
>> +	}
>> +
>> +	if (!is_priv_gfn) {
>> +		/* Not a private mapping, handling normally */
>> +		return -EINVAL;
>> +	}
>> +
>> +	ret = kvm_mmu_topup_memory_cache(memcache,
>> +					 kvm_mmu_cache_min_pages(vcpu->arch.hw_mmu));
>> +	if (ret)
>> +		return ret;
>> +
>> +	ret = kvm_gmem_get_pfn(kvm, memslot, gfn, &pfn, &page, NULL);
>> +	if (ret)
>> +		return ret;
>> +
>> +	/* FIXME: Should be able to use bigger than PAGE_SIZE mappings */
>> +	ret = realm_map_ipa(kvm, fault_ipa, pfn, PAGE_SIZE, KVM_PGTABLE_PROT_W,
>> +			    memcache);
>> +	if (!ret)
>> +		return 1; /* Handled */
>> +
>> +	put_page(page);
>> +	return ret;
>> +}

I also found the names confusing. Can we do

modified   arch/arm64/kvm/mmu.c
@@ -1487,7 +1487,7 @@ static int private_memslot_fault(struct kvm_vcpu *vcpu,
 	struct kvm *kvm = vcpu->kvm;
 	gpa_t gpa = kvm_gpa_from_fault(kvm, fault_ipa);
 	gfn_t gfn = gpa >> PAGE_SHIFT;
-	bool priv_exists = kvm_mem_is_private(kvm, gfn);
+	bool is_priv_gfn = kvm_mem_is_private(kvm, gfn);
 	struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;
 	struct page *page;
 	kvm_pfn_t pfn;
@@ -1497,19 +1497,19 @@ static int private_memslot_fault(struct kvm_vcpu *vcpu,
 	 * the top bit set. Thus is the fault address matches the GPA then it
 	 * is the private alias.
 	 */
-	bool is_priv_gfn = (gpa == fault_ipa);
+	bool is_priv_fault = (gpa == fault_ipa);
 
-	if (priv_exists != is_priv_gfn) {
+	if (is_priv_gfn != is_priv_fault) {
 		kvm_prepare_memory_fault_exit(vcpu,
 					      gpa,
 					      PAGE_SIZE,
 					      kvm_is_write_fault(vcpu),
-					      false, is_priv_gfn);
+					      false, is_priv_fault);
 
 		return 0;
 	}
 
-	if (!is_priv_gfn) {
+	if (!is_priv_fault) {
 		/* Not a private mapping, handling normally */
 		return -EINVAL;
 	}