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

[Sean Christopherson]

On Wed, Feb 08, 2023, Isaku Yamahata wrote:
> 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.

Why?  I'd rather keep the two things separate.  If we enforce this sort of thing
at KVM_SET_MEMORY_ATTRIBUTES, then we also have to enforce it at
KVM_SET_USER_MEMORY_REGION.