Re: [Xen-devel] [PATCH for-4.12 v2 2/2] xen/arm: Stop relocating Xen

[Julien Grall <julien.grall@xxxxxxx>]

On 12/18/18 12:09 PM, Andrii Anisov wrote:
> Hello Julien,
Hi,

> On 17.12.18 19:34, Andrii Anisov wrote:
> > I see something like following as a quick WA (not even build tested):
> >
> > diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> > index d2c63a8..bf72ba9 100644
> > --- a/xen/arch/arm/domain_build.c
> > +++ b/xen/arch/arm/domain_build.c
> > @@ -223,8 +223,9 @@ fail:
> >    * meet these requirements directly. So instead of proceed as follows:
> >    *
> >    * We first allocate the largest allocation we can as low as we
> > - * can. This then becomes the first bank. This bank must be at least
> > - * 128MB (or dom0_mem if that is smaller).
> > + * can. This then becomes the first bank. This bank is at least 128MB 
> > even if
> > + * dom0 is configured for less. It is the way to get that bank 128MB 
> > aligned,
> > + * what is required for 32-bit zImage.
> >    *
> >    * Then we start allocating more memory, trying to allocate the
> >    * largest possible size and trying smaller sizes until we
> > @@ -253,7 +254,7 @@ static void __init allocate_memory_11(struct 
> > domain *d,
> >                                         struct kernel_info *kinfo)
> >   {
> >       const unsigned int min_low_order =
> > -        get_order_from_bytes(min_t(paddr_t, dom0_mem, MB(128)));
> > +        get_order_from_bytes(MB(128));
> >       const unsigned int min_order = get_order_from_bytes(MB(4));
> >       struct page_info *pg;
> >       unsigned int order = get_allocation_size(kinfo->unassigned_mem);
> > @@ -268,6 +269,10 @@ static void __init allocate_memory_11(struct 
> > domain *d,
> >        */
> >       BUG_ON(!is_domain_direct_mapped(d));
> >
> > +    if ( dom0_mem < MB(128))
> > +        printk(XENLOG_WARNING "Allocating 128MB for Domain0 with 
> > %"PRIu64"MB\n",
> > +               dom0_mem/MB(1));
> > +
> >       printk("Allocating 1:1 mappings totalling %ldMB for dom0:\n",
> >              /* Don't want format this as PRIpaddr (16 digit hex) */
> >              (unsigned long)(kinfo->unassigned_mem >> 20));
> >
> >
> > But I'm not sure if it worth to be sent, because I'm going to rewrite 
> > it soon.
>  From the second thought, we have last posting date for 4.12 already in 
> the past. So redesign will not go to 4.12.
> Maybe it worth to have the thing above as a bugfix for 4.12?
> What do you think?
AFAICT, it was possible to boot a Dom0 with only 64MB on Arm64. So I am 
not entirely why we would also limit the size there.
For Arm32, I think we should just return an error and fail the domain 
build. If you ask 64MB and we give you 128MB then something is already 
really wrong.
Anyway, I think this should be submitted properly to discuss for Xen 
4.12 inclusion.
Cheers,

--
Julien Grall

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