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@xxxxxxxxxxxxxxx> 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.