Re: [Xen-devel] [PATCH v1 6/9] livepatch: Initial ARM64 support.

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Mon, Aug 15, 2016 at 04:57:26PM +0200, Julien Grall wrote:
> Hi Jan and Konrad,
> 
> On 15/08/2016 16:23, Jan Beulich wrote:
> > > > > On 15.08.16 at 16:09, <konrad.wilk@xxxxxxxxxx> wrote:
> > > On Mon, Aug 15, 2016 at 02:21:48AM -0600, Jan Beulich wrote:
> > > > > > > On 15.08.16 at 01:07, <konrad.wilk@xxxxxxxxxx> wrote:
> > > > > @@ -711,9 +711,15 @@ static int prepare_payload(struct payload 
> > > > > *payload,
> > > > >                  return -EINVAL;
> > > > >              }
> > > > >          }
> > > > > +#ifndef CONFIG_ARM
> > > > >          apply_alternatives_nocheck(start, end);
> > > > > +#else
> > > > > +        apply_alternatives(start, sec->sec->sh_size);
> > > > > +#endif
> > > > 
> > > > Conditionals like this are ugly - can't this be properly abstracted?
> > > 
> > > Yes, I can introduce an apply_alternatives_nocheck on ARM that will
> > > hava the same set of arguments on x86.
> > > 
> > > Or I can make a new function name?
> > 
> > Either way is fine with me, with a slight preference to the former
> > one.
> 
> I am fine with the prototype of the function apply_alternatives_nocheck but
> I don't think the name is relevant for ARM.
> 
> Is there any reason we don't want to call directly apply_alternatives in
> x86?

It assumes (and has an ASSERT) that it is called with interrupts disabled.
And we don't need to do that (as during livepatch loading we can modify the
livepatch payload without worrying about interrupts).

P.S.
loading != applying.

I could do a patch where we rename 'apply_alternatives' -> 
'apply_alternatives_boot'
and 'apply_alternatives_nocheck' to 'apply_alternatives'.

Also the x86 version instead of having:

apply_alternatives(struct alt_instr *start, struct alt_instr *end)

would end up with:

apply_alternatives(void *start, size_t length)

to comply with ARM version.
> 
> Regards,
> 
> -- 
> Julien Grall

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