Re: [Qemu-devel] vhost-user: broken mem regions

[Michael S. Tsirkin]

On Wed, Jun 25, 2014 at 03:46:04PM +0000, Damjan Marion (damarion) wrote:
> 
> On 25 Jun 2014, at 17:29, Michael S. Tsirkin <address@hidden> wrote:
> 
> > On Wed, Jun 25, 2014 at 02:57:52PM +0000, Damjan Marion (damarion) wrote:
> >> 
> >> On 25 Jun 2014, at 16:27, Michael S. Tsirkin <address@hidden> wrote:
> >> 
> >>> On Wed, Jun 25, 2014 at 02:20:56PM +0000, Damjan Marion (damarion) wrote:
> >>>> 
> >>>> On 25 Jun 2014, at 16:13, Nikolay Nikolaev <address@hidden> wrote:
> >>>> 
> >>>>>>> - it will require changes on the user side also
> >>>>>> 
> >>>>>> why would it?
> >>>>>> format seems unchanged, right?
> >>>>> 
> >>>>> yes, but it will happen that multiple regions have same FD so call to 
> >>>>> mmap()
> >>>>> should look different, I’m still playing with this on user side...
> >>>>> but then you shoudl somehow accumulate the sizes and send just a single 
> >>>>> fd, something along these lines. 
> >>>> 
> >>>> Yes, so I’m not very happy with that approach and looking if there is 
> >>>> better proposal, 
> >>>> or at least wider agreement how to address this issue.
> >>>> 
> >>>> Damjan
> >>> 
> >>> still not sure what the issue is ...
> >>> 
> >> 
> >> No issue, just additional logic is needed on user side to calculate total 
> >> size of shared regions and call mmap() once per FD.
> >> 
> >> Agree?
> > 
> > why not just call it multiple times? AFAIK linux handles this just fine.
> 
> I need to specify size when calling mmap(), so i need to run trough all 
> regions and sum sizes before calling mmap().

You can map same file in many places.
Just call mmap many times with offsets.

-- 
MST