Re: [PATCH 6/7] xen/guest_access: Consolidate guest access helpers in xen/guest_access.h

[Julien Grall <julien@xxxxxxx>]

Ping 2.

On 29/04/2020 15:04, Julien Grall wrote:
> Hi,
>
> Gentle ping. Any comments on the direction to take?
>
> On 09/04/2020 10:28, Julien Grall wrote:
> > On 09/04/2020 09:06, Jan Beulich wrote:
> > > On 09.04.2020 10:01, Julien Grall wrote:
> > > > Hi,
> > > >
> > > > On 09/04/2020 07:30, Jan Beulich wrote:
> > > > > On 09.04.2020 00:05, Julien Grall wrote:
> > > > > I don't see why a new port may not also want
> > > > > to go that route instead of the x86/Arm one.
> > > > I could accept that someone would want to reinvent a new ABI
> > > > from scratch for just an hypothetical new arch. However it would
> > > > be quite an effort to reinvent XEN_GUEST_HANDLE(). The chance is
> > > > RISC-V is only going to re-use what Arm did as Arm already did
> > > > with x86.
> > > >
> > > > I would like to avoid to introduce a new directory asm-generic
> > > > with just one header in it. Maybe you have some other headers in
> > > > mind?
> > > I recall having wondered a few times whether we shouldn't use this
> > > concept elsewhere. One case iirc was bitops stuff. Looking over
> > > the Linux ones, some atomic and barrier fallback implementations
> > > may also sensibly live there, and there are likely more.
> > In theory it makes sense but, in the current state of Xen, 
> > 'asm-generic' means they are common to Arm and x86. This is basically 
> > the same definition as for the directory 'xen'. So how do you draw a 
> > line which files go where?
> > To be honest, I don't think we can draw a line without a 3rd 
> > architecture. So I would recommend to wait until then to create an 
> > asm-generic directory.
> > Meanwhile, I still think the consolidation in xen/ is useful as it 
> > makes easier to maintain. It is also going to make easier for RISCv 
> > (or a new arch) as they don't have to worry about duplication (if any).
> > In the event they decide to purse their own route, then it is not 
> > going to be a massive pain to move part of xen/guest_access.h in 
> > asm-generic/guest_access.h and include the latter from {xen, asm} 
> > /guest_access.h.
> Cheers,
--
Julien Grall