On Mon, Jul 24, 2023, Xu Yilun wrote:
> On 2023-07-18 at 16:44:51 -0700, Sean Christopherson wrote:
> > @@ -1346,6 +1350,9 @@ static void kvm_destroy_vm(struct kvm *kvm)
> > kvm_free_memslots(kvm, &kvm->__memslots[i][0]);
> > kvm_free_memslots(kvm, &kvm->__memslots[i][1]);
> > }
> > +#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
> > + xa_destroy(&kvm->mem_attr_array);
> > +#endif
>
> Is it better to make the destruction in reverse order from the creation?
Yeah. It _shoudn't_ matter, but there's no reason not keep things tidy and
consistent.
> To put xa_destroy(&kvm->mem_attr_array) after cleanup_srcu_struct(&kvm->srcu),
> or put xa_init(&kvm->mem_attr_array) after init_srcu_struct(&kvm->irq_srcu).
The former, because init_srcu_struct() can fail (allocates memory), whereas
xa_init() is a "pure" initialization routine.
> > cleanup_srcu_struct(&kvm->irq_srcu);
> > cleanup_srcu_struct(&kvm->srcu);
> > kvm_arch_free_vm(kvm);
> > @@ -2346,6 +2353,145 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
> > }
> > #endif /* CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */
>
> [...]
>
> > +static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
> > + struct kvm_memory_attributes *attrs)
> > +{
> > + gfn_t start, end;
> > +
> > + /* flags is currently not used. */
> > + if (attrs->flags)
> > + return -EINVAL;
> > + if (attrs->attributes & ~kvm_supported_mem_attributes(kvm))
> > + 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;
>
> As the attrs->address/size are both garanteed to be non-zero, non-wrap
> and page aligned in prevous check. Is it OK to simplify the calculation,
> like:
>
> end = (attrs->address + attrs->size) >> PAGE_SHIFT;
Yes, that should work.
Chao, am I missing something? Or did we just end up with unnecessarly convoluted
code as things evolved?
> > +
> > + if (WARN_ON_ONCE(start == end))
> > + return -EINVAL;
>
> Also, is this check possible to be hit? Maybe remove it?
It should be impossible to, hence the WARN. I added the check for two reasons:
(1) to help document that end is exclusive, and (2) to guard against future bugs.
