Re: [PATCH V2 3/4] xen/unpopulated-alloc: Add mechanism to use Xen resource

[Oleksandr <olekstysh@xxxxxxxxx>]

On 28.10.21 22:08, Boris Ostrovsky wrote:

Hi Boris

I am sorry for the late response.

> On 10/26/21 12:05 PM, Oleksandr Tyshchenko wrote:
> >   +static void unpopulated_init(void)
> > +{
> > +    static bool inited = false;
> > +    int ret;
> > +
> > +    if (inited)
> > +        return;
> > +
> > +    /*
> > +     * Try to initialize Xen resource the first and fall back to 
> > default
> > +     * resource if arch doesn't offer one.
> > +     */
> > +    ret = arch_xen_unpopulated_init(&xen_resource);
> > +    if (!ret)
> > +        target_resource = &xen_resource;
> > +    else if (ret == -ENOSYS)
> > +        target_resource = &iomem_resource;
> > +    else
> > +        pr_err("Cannot initialize Xen resource\n");
>
> I'd pass target_resource as a parameter to arch_xen_unpopulated_init() 
> instead. Default routine will assign it iomem_resource and you won't 
> have to deal with -ENOSYS.
That would be much better, thank you. Will do.


> Also, what happens in case of error? Is it fatal? I don't think your 
> changes in fill_list() will work.
The error is fatal as we don't have a suitable resource to allocate a 
region from, and yes, the fill_list() must not be called.

> > +
> > +    inited = true;
>
> I agree with Stefano in that it would be better to call this from an 
> init function, and you won't have t worry about multiple calls here.
Yes, that's good point, thank you. Will do.


> -boris
--
Regards,

Oleksandr Tyshchenko