Re: [Xen-devel] [PATCH] arm:cpuerrata: Align a virtual address before unmap

[Julien Grall <julien.grall@xxxxxxx>]

On 7/18/19 3:08 PM, Andrii Anisov wrote:
> Hello Julien,
Hi,

> On 18.07.19 16:44, Julien Grall wrote:
> > > My suggestion about vunmap() still stands though.
> > +1 for the vunmap solution.
> It was my initial idea.
>
> But, the issue is introduced by change 9cc0618. In particular, by the 
> check in `xen_pt_update()`
>      if ( !IS_ALIGNED(virt, PAGE_SIZE) )
>      {
>          mm_printk("The virtual address is not aligned to the 
> page-size.\n");
>          return -EINVAL;
>      }
>
> So I assumed you had some specific idea about that check.
I am expecting all the callers to properly align the address.

> I'd fix `xen_pt_update()` if you are ok with it.
Please no. The interfaces are already pretty horrible as it mixing 
address and frame. So this check here is partially closing the gap of 
passing misaligned virtual address.
If you look at the x86 counter-part, they also assume the address is 
aligned (see ASSERT in some of the helpers). So I think the proper way 
to go is aligning the address in vumap.
As Andrew pointed out, this also makes the interface more consistent 
with how {,un}map_domain_page() currently works.
Cheers,

--
Julien Grall

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