Re: [PATCH v6 3/4] of: reserved_mem: Use unflatten_devicetree APIs to scan reserved memory nodes

[Klara Modin <klarasmodin@xxxxxxxxx>]

On 2024-07-05 15:05, Klara Modin wrote:
> Hi,
>
> On 2024-05-29 00:36, Oreoluwa Babatunde wrote:
> > The unflatten_devicetree APIs have been setup and are available to be
> > used by the time the fdt_init_reserved_mem() function is called.
> > Since the unflatten_devicetree APIs are a more efficient way of scanning
> > through the DT nodes, switch to using these APIs to facilitate the rest
> > of the reserved memory processing.
>
> With this patch series, I've observed significantly less memory 
> available to userspace on my Raspberry Pi 1 and 3.
>
> I see this message on the kernel console:
> Jul  4 23:13:49 bonnet kernel: OF: reserved mem: 0x1b000000..0x1effffff 
> (65536 KiB) map non-reusable linux
>
> where it was previously marked as reusable:
> Jul  4 22:23:22 bonnet kernel: OF: reserved mem: 0x1b000000..0x1effffff 
> (65536 KiB) map reusable linux,cma
>
> If I look at bcm283x.dtsi, it definitely has the reusable property.
>
> I've below pointed out the snippet I think could be suspicous.
>
> > Signed-off-by: Oreoluwa Babatunde <quic_obabatun@xxxxxxxxxxx>
> > ---
> >   drivers/of/of_reserved_mem.c    | 93 ++++++++++++++++++++-------------
> >   include/linux/of_reserved_mem.h |  2 +-
> >   kernel/dma/coherent.c           | 10 ++--
> >   kernel/dma/contiguous.c         |  8 +--
> >   kernel/dma/swiotlb.c            | 10 ++--
> >   5 files changed, 72 insertions(+), 51 deletions(-)
> >
> > diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
> > index 113d593ea031..05283cd24c3b 100644
> > --- a/drivers/of/of_reserved_mem.c
> > +++ b/drivers/of/of_reserved_mem.c

> > @@ -447,7 +476,7 @@ static int __init 
> > __reserved_mem_alloc_size(unsigned long node, const char *unam
> >                  uname, (unsigned long)(size / SZ_1M));
> >           return -ENOMEM;
> >       }
>
>
> > -    fdt_reserved_mem_save_node(node, uname, base, size);
> > +    fdt_reserved_mem_save_node(NULL, uname, base, size);
>
> This could perhaps be suspicious?
>
> The above message seems to come from of_init_reserved_mem_node when
> called from of_reserved_mem_save_node when called from here. This would 
> mean that the node is not actually saved to rmem and thus not marked 
> reusable?
>
>
> >       return 0;
> >   }

> Regards,
> Klara Modin

Attaching kernel logs of old and new behavior, and my config for reference.

Attachment: config.gz
Description: application/gzip

Attachment: kern-new.log.gz
Description: application/gzip

Attachment: kern-old.log.gz
Description: application/gzip