Re: [PATCH] Use EfiACPIReclaimMemory for ESRT

[Jan Beulich <jbeulich@xxxxxxxx>]

On 30.09.2022 23:02, Demi Marie Obenour wrote:
> As discussed on xen-devel, using EfiRuntimeServicesData for more than is
> absolutely necessary is a bad idea.
> ---
>  xen/common/efi/boot.c | 19 +++++++++++--------
>  1 file changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
> index 
> db0340c8e2628314226c618dda11ede4c62fdf3b..dba23439758d1e842d267dcd19448e0f9113b115
>  100644
> --- a/xen/common/efi/boot.c
> +++ b/xen/common/efi/boot.c
> @@ -601,11 +601,13 @@ static size_t __init get_esrt_size(const 
> EFI_MEMORY_DESCRIPTOR *desc)
>      if ( physical_start > esrt || esrt - physical_start >= len )
>          return 0;
>      /*
> -     * The specification requires EfiBootServicesData, but accept
> -     * EfiRuntimeServicesData, which is a more logical choice.
> +     * The specification requires EfiBootServicesData, but also accept
> +     * EfiRuntimeServicesData (for compatibility) and EfiACPIReclaimMemory
> +     * (which will contain the tables after successful kexec).

What's the compatibility concern here? We haven't released any Xen
version yet where the table would be moved to EfiRuntimeServicesData.

Jan

>       */
>      if ( (desc->Type != EfiRuntimeServicesData) &&
> -         (desc->Type != EfiBootServicesData) )
> +         (desc->Type != EfiBootServicesData) &&
> +         (desc->Type != EfiACPIReclaimMemory) )
>          return 0;
>      available_len = len - (esrt - physical_start);
>      if ( available_len <= offsetof(EFI_SYSTEM_RESOURCE_TABLE, Entries) )
> @@ -1144,18 +1146,19 @@ static void __init efi_relocate_esrt(EFI_SYSTEM_TABLE 
> *SystemTable)
>      for ( i = 0; i < info_size; i += mdesc_size )
>      {
>          /*
> -         * ESRT needs to be moved to memory of type EfiRuntimeServicesData
> +         * ESRT needs to be moved to memory of type EfiACPIReclaimMemory
>           * so that the memory it is in will not be used for other purposes.
>           */
>          void *new_esrt = NULL;
> -        size_t esrt_size = get_esrt_size(memory_map + i);
> +        const EFI_MEMORY_DESCRIPTOR *desc = memory_map + i;
> +        size_t esrt_size = get_esrt_size(desc);
>  
>          if ( !esrt_size )
>              continue;
> -        if ( ((EFI_MEMORY_DESCRIPTOR *)(memory_map + i))->Type ==
> -             EfiRuntimeServicesData )
> +        if ( desc->Type == EfiRuntimeServicesData ||
> +             desc->Type == EfiACPIReclaimMemory )
>              break; /* ESRT already safe from reuse */
> -        status = efi_bs->AllocatePool(EfiRuntimeServicesData, esrt_size,
> +        status = efi_bs->AllocatePool(EfiACPIReclaimMemory, esrt_size,
>                                        &new_esrt);
>          if ( status == EFI_SUCCESS && new_esrt )
>          {