Re: [PATCH v8] Preserve the EFI System Resource Table for dom0

[Jan Beulich <jbeulich@xxxxxxxx>]

On 24.06.2022 20:17, Demi Marie Obenour wrote:
> The EFI System Resource Table (ESRT) is necessary for fwupd to identify
> firmware updates to install.  According to the UEFI specification §23.4,
> the ESRT shall be stored in memory of type EfiBootServicesData.  However,
> memory of type EfiBootServicesData is considered general-purpose memory
> by Xen, so the ESRT needs to be moved somewhere where Xen will not
> overwrite it.  Copy the ESRT to memory of type EfiRuntimeServicesData,
> which Xen will not reuse.  dom0 can use the ESRT if (and only if) it is
> in memory of type EfiRuntimeServicesData.
> 
> Earlier versions of this patch reserved the memory in which the ESRT was
> located.  This created awkward alignment problems, and required either
> splitting the E820 table or wasting memory.  It also would have required
> a new platform op for dom0 to use to indicate if the ESRT is reserved.
> By copying the ESRT into EfiRuntimeServicesData memory, the E820 table
> does not need to be modified, and dom0 can just check the type of the
> memory region containing the ESRT.  The copy is only done if the ESRT is
> not already in EfiRuntimeServicesData memory, avoiding memory leaks on
> repeated kexec.
> 
> See https://lore.kernel.org/xen-devel/20200818184018.GN1679@mail-itl/T/
> for details.
> 
> Signed-off-by: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
with one further adjustment:

> @@ -1051,6 +1110,70 @@ static void __init 
> efi_set_gop_mode(EFI_GRAPHICS_OUTPUT_PROTOCOL *gop, UINTN gop
>  #define INVALID_VIRTUAL_ADDRESS (0xBAAADUL << \
>                                   (EFI_PAGE_SHIFT + BITS_PER_LONG - 32))
>  
> +static void __init efi_relocate_esrt(EFI_SYSTEM_TABLE *SystemTable)
> +{
> +    EFI_STATUS status;
> +    UINTN info_size = 0, map_key, mdesc_size;
> +    void *memory_map = NULL;
> +    UINT32 ver;
> +    unsigned int i;
> +
> +    for ( ; ; ) {

In reply to v7 I said:

"Nit: Style:

    for ( ; ; )
    {
"

which you've dealt with just partly. This time I'll take care of this
while committing.

Also for future patches please remember that having brief per-revision
change notes are quite helpful to reviewers.

Jan