Re: [Qemu-devel] [PATCH] memory: do not do out of bound notification

[Peter Xu]

On Thu, Jun 20, 2019 at 03:14:04PM +0200, Paolo Bonzini wrote:
> On 20/06/19 14:59, Peter Xu wrote:
> > I feel like this can be problematic.  I'm imaging:
> > 
> > start=0x1000_0000, size=0x1000_1000
> > 
> > This will get size=0x1000 but actually we can do size=0x1000_0000 as
> > the first.
> 
> Right, we can do:
> 
> /*
>  * If a naturally aligned region starting at "start" ends before "end",
>  * use it.  Otherwise, keep the lowest bit of size.
>  */
> if (size > (start & -start))
>     size = start & -start;

May need to consider start==0, otherwise size will be zero here?

> else
>     size = size & -size;

Should use MSB rather than LSB of size?

> 
> >>
> >> +        trace_vtd_as_unmap_whole(pci_bus_num(as->bus),
> >> +                                 VTD_PCI_SLOT(as->devfn),
> >> +                                 VTD_PCI_FUNC(as->devfn),
> >> +                                 entry.iova, size);
> > 
> > Can move this out because this is a trace only so we don't have
> > restriction on mask?
> > 
> >>
> >> -    map.iova = entry.iova;
> >> -    map.size = entry.addr_mask;
> >> -    iova_tree_remove(as->iova_tree, &map);
> >> +        map.iova = entry.iova;
> >> +        map.size = entry.addr_mask;
> >> +        iova_tree_remove(as->iova_tree, &map);
> > 
> > Same here?
> > 
> 
> Yes, I would move these and the iova_tree_remove outside the loop, while
> keeping entry's initialization inside looks cleaner.

Yeah that's ok to me too.

Thanks,

-- 
Peter Xu