Re: [Xen-devel] [PATCH v2] xen/arm: during efi boot, improve the check for usable memory

[Julien Grall <julien@xxxxxxx>]

Hi Stefano,

On 14/01/2020 23:31, Stefano Stabellini wrote:
> When booting via EFI, the EFI memory map has information about memory
> regions and their type. Improve the check for the type and attribute of
> each memory region to figure out whether it is usable memory or not.
> This patch brings the check on par with Linux v5.5-rc6 and makes more
> memory reusable as normal memory by Xen (except that Linux also reuses
> EFI_PERSISTENT_MEMORY, which we do not).
>
> Specifically, this patch also reuses memory marked as
> EfiLoaderCode/Data, and it uses both Attribute and Type for the check
> (Attribute needs to be EFI_MEMORY_WB).
>
> Reported-by: Roman Shaposhnik <roman@xxxxxxxxxx>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
> CC: Julien Grall <julien@xxxxxxx>
Acked-by: Julien Grall <julien@xxxxxxx>

Cheers,

> ---
> Changes in v2:
> - improve commit message
> - do not allocate memory marked as EFI_PERSISTENT_MEMORY
> - do not change map_bs' behavior
> ---
>   xen/arch/arm/efi/efi-boot.h | 11 +++++++----
>   1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/xen/arch/arm/efi/efi-boot.h b/xen/arch/arm/efi/efi-boot.h
> index d7bf934077..6527cb0bdf 100644
> --- a/xen/arch/arm/efi/efi-boot.h
> +++ b/xen/arch/arm/efi/efi-boot.h
> @@ -149,10 +149,13 @@ 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 ||
> +              (!map_bs &&
> +               (desc_ptr->Type == EfiBootServicesCode ||
> +                desc_ptr->Type == EfiBootServicesData))) )
>           {
>               if ( !meminfo_add_bank(&bootinfo.mem, desc_ptr) )
>               {
--
Julien Grall

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