Re: [Xen-devel] REGRESSION: Xen 4.13 RC5 fails to bootstrap Dom0 on ARM

[Roman Shaposhnik <roman@xxxxxxxxxx>]

On Thu, Dec 19, 2019 at 4:01 PM Stefano Stabellini
<sstabellini@xxxxxxxxxx> wrote:
>
> On Thu, 19 Dec 2019, Julien Grall wrote:
> > > > In fact most of people on Arm are using GRUB rather than EFI directly as
> > > > this is more friendly to use.
> > > >
> > > > Regarding the devicetree, Xen and Linux will completely ignore the
> > > > memory nodes in Xen if using EFI. This because the EFI memory map will
> > > > give you an overview of the platform with the EFI regions included.
> > >
> > > Aha! So in that sense it is a bug in Xen after all, right? (that's what
> > > you're
> > > referring to when you say you now understand what needs to get fixed).
> >
> > Yes. The EFI memory map is a list of existing memory with a type associated 
> > to
> > it (Conventional, BootServiceCodes, MemoryMappedIO...).
> >
> > The OS/Hypervisor will have to go through them and check which regions are
> > usuable. Compare to Linux, Xen has limited itself to only a few types.
> >
> > However, I think we can be on a par with Linux here.
>
> I gave a look at the Linux implementation, the interesting bit is
> drivers/firmware/efi/arm-init.c:is_usable_memory as far as I can tell.
> I also gave a look at the Xen side, which is
> xen/arch/arm/efi/efi-boot.h:efi_process_memory_map_bootinfo. As guessed,
> the two are not quite the same.
>
> One of the main differences is that Linux uses as "System RAM" even
> regions that were marked as EFI_BOOT_SERVICES_CODE/DATA and
> EFI_LOADER_CODE/DATA because they will get freed anyway. Xen doesn't
> do that unless map_bs is set.
>
> I wrote a quick patch to implement the Linux behavior on Xen, only
> lightly tested. I can confirm that I see more memory this way. However,
> I am not sure we actually want to import the Linux behavior wholesale.
>
> Anyway, Roman, could you please let me know if this patch solves the
> issue?

Tried the attached patch -- but it seems I can't boot at all with this. Xen
doesn't print anything on the console either.

To Julien's point -- should I reduce the # of types and try again?

Thanks,
Roman.

>
>
>
> diff --git a/xen/arch/arm/efi/efi-boot.h b/xen/arch/arm/efi/efi-boot.h
> index ca655ff003..ad18ff3669 100644
> --- a/xen/arch/arm/efi/efi-boot.h
> +++ b/xen/arch/arm/efi/efi-boot.h
> @@ -149,10 +149,14 @@ static EFI_STATUS __init 
> efi_process_memory_map_bootinfo(EFI_MEMORY_DESCRIPTOR *
>
>      for ( Index = 0; Index < (mmap_size / desc_size); Index++ )
>      {
> -        if ( desc_ptr->Type == EfiConventionalMemory ||
> -             (!map_bs &&
> -              (desc_ptr->Type == EfiBootServicesCode ||
> -               desc_ptr->Type == EfiBootServicesData)) )
> +        if ( desc_ptr->Attribute == EFI_MEMORY_WB &&
> +             (desc_ptr->Type == EfiConventionalMemory ||
> +              desc_ptr->Type == EfiLoaderCode ||
> +              desc_ptr->Type == EfiLoaderData ||
> +              desc_ptr->Type == EfiACPIReclaimMemory ||
> +              desc_ptr->Type == EfiPersistentMemory ||
> +              desc_ptr->Type == EfiBootServicesCode ||
> +              desc_ptr->Type == EfiBootServicesData) )
>          {
>              if ( !meminfo_add_bank(&bootinfo.mem, desc_ptr) )
>              {
> diff --git a/xen/include/efi/efidef.h b/xen/include/efi/efidef.h
> index 86a7e111bf..f46207840f 100644
> --- a/xen/include/efi/efidef.h
> +++ b/xen/include/efi/efidef.h
> @@ -147,6 +147,7 @@ typedef enum {
>      EfiMemoryMappedIO,
>      EfiMemoryMappedIOPortSpace,
>      EfiPalCode,
> +    EfiPersistentMemory,
>      EfiMaxMemoryType
>  } EFI_MEMORY_TYPE;
>

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