Re: [PATCH v10 2/9] KVM: Introduce per-page memory attributes

[Isaku Yamahata]

On Fri, Dec 02, 2022 at 02:13:40PM +0800,
Chao Peng <chao.p.peng@linux.intel.com> wrote:

> +static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
> +                                        struct kvm_memory_attributes *attrs)
> +{
> +     gfn_t start, end;
> +     unsigned long i;
> +     void *entry;
> +     u64 supported_attrs = kvm_supported_mem_attributes(kvm);
> +
> +     /* flags is currently not used. */
> +     if (attrs->flags)
> +             return -EINVAL;
> +     if (attrs->attributes & ~supported_attrs)
> +             return -EINVAL;
> +     if (attrs->size == 0 || attrs->address + attrs->size < attrs->address)
> +             return -EINVAL;
> +     if (!PAGE_ALIGNED(attrs->address) || !PAGE_ALIGNED(attrs->size))
> +             return -EINVAL;
> +
> +     start = attrs->address >> PAGE_SHIFT;
> +     end = (attrs->address + attrs->size - 1 + PAGE_SIZE) >> PAGE_SHIFT;
> +
> +     entry = attrs->attributes ? xa_mk_value(attrs->attributes) : NULL;
> +
> +     mutex_lock(&kvm->lock);
> +     for (i = start; i < end; i++)
> +             if (xa_err(xa_store(&kvm->mem_attr_array, i, entry,
> +                                 GFP_KERNEL_ACCOUNT)))
> +                     break;
> +     mutex_unlock(&kvm->lock);
> +
> +     attrs->address = i << PAGE_SHIFT;
> +     attrs->size = (end - i) << PAGE_SHIFT;
> +
> +     return 0;
> +}
> +#endif /* CONFIG_HAVE_KVM_MEMORY_ATTRIBUTES */
> +

If memslot isn't private, it should return error if private attribute is set.
Something like following check is needed.

+       if (attrs->flags & KVM_MEM_PRIVATE) {
+               /* non-private memory slot doesn't allow KVM_MEM_PRIVATE */
+               for (i = 0; i < kvm_arch_nr_memslot_as_ids(kvm); i++) {
+                       struct kvm_memslot_iter iter;
+                       struct kvm_memslots *slots;
+
+                       slots = __kvm_memslots(kvm, i);
+                       kvm_for_each_memslot_in_gfn_range(&iter, slots, start, 
end) {
+                               if (!kvm_slot_can_be_private(iter.slot)) {
+                                       mutex_unlock(&kvm->slots_lock);
+                                       return -EINVAL;
+                               }
+                       }
+               }
+       }
+


-- 
Isaku Yamahata <isaku.yamahata@gmail.com>