Re: [RFC v2 3/8] xen/arm: Export host device-tree to hypfs

[Oleksii Moisieiev <Oleksii_Moisieiev@xxxxxxxx>]

On Wed, Feb 09, 2022 at 07:34:57PM +0000, Julien Grall wrote:
> Hi,
> 
> On 09/02/2022 18:51, Oleksii Moisieiev wrote:
> > On Wed, Feb 09, 2022 at 12:17:17PM +0000, Julien Grall wrote:
> > > > > > +static HYPFS_DIR_INIT_FUNC(host_dt_dir, HOST_DT_DIR, 
> > > > > > &host_dt_dir_funcs);
> > > > > > +
> > > > > > +static int __init host_dtb_export_init(void)
> > > > > > +{
> > > > > > +    ASSERT(dt_host && (dt_host->sibling == NULL));
> > > > > 
> > > > > dt_host can be NULL when booting on ACPI platform. So I think this 
> > > > > wants to
> > > > > be turned to a normal check and return directly.
> > > > > 
> > > > 
> > > > I will replace if with
> > > > if ( !acpi_disabled )
> > > >       return -ENODEV;
> > > > 
> > > > > Also could you explain why you need to check dt_host->sibling?
> > > > > 
> > > > 
> > > > This is my way to check if dt_host points to the top of the device-tree.
> > > > In any case I will replace it with !acpi_disabled as I mentioned
> > > > earlier.
> > > 
> > > dt_host will always points to the root of the host device-tree. I don't
> > > think it is the job of hypfs to enforce it unless you expect the code to 
> > > be
> > > buggy if this happens. But then I would argue the code should be hardened.
> > > 
> > 
> > Hi Julien,
> > 
> > Unfortunatelly I can't use acpi_disabled in host_dtb_export_init because
> > I've already moved host_dtb_export.c to the common folder.
> 
> I am sorry, but I don't understand why moving the code to common code
> prevents you to use !acpi_disabled. Can you clarify?
> 
Sorry, my bad. I thought that acpi_disabled is defined only for arm. Now
I've rechecked and see I was wrong.

> > 
> > As for the host->sibling - I took the whole assert:
> > ASSERT(dt_host && (dt_host->sibling == NULL));
> > from the prepare_dtb_hwdom function. And this assertion was added by the
> > commit b8f1c5e7039efbe1103ed3fe4caedf8c34affe13 authored by you.
> 
> I am not sure what's your point... Yes I wrote the same ASSERT() 9 years
> time. But people view evolves over the time.
> 
> There are some code I wished I had written differently (How about you? ;)).
> However, I don't have the time to rewrite everything I ever wrote. That
> said, I can at least make sure they are not spread.
> 

I'm sorry, I didn't mean to be rude. I've just tried to tell where I
took this assertion from.

> > 
> > What do you think if I omit dt_host->sibling check and make it:
> > 
> > if ( !dt_host )
> >      return -ENODEV;
> 
> We used to set dt_host even when booting with ACPI but that shouldn't be the
> case anymore. So I think this check should be fine.
> 

Ok, thank you. I'll do the change.

Best regards,
Oleksii.