[U-Boot] [PATCH v2 4/8] x86: Tidy up selection of building the EFI stub

[Bin Meng]

Hi Alex,

On Thu, Sep 29, 2016 at 3:13 PM, Alexander Graf <agraf at suse.de> wrote:
> On 09/29/2016 07:37 AM, Bin Meng wrote:
>>
>> Hi Alex,
>>
>> On Thu, Sep 29, 2016 at 1:08 PM, Alexander Graf <agraf at suse.de> wrote:
>>>
>>>
>>> Am 29.09.2016 um 05:37 schrieb Bin Meng <bmeng.cn at gmail.com>:
>>>
>>> Hi Simon,
>>>
>>> On Wed, Sep 28, 2016 at 10:43 PM, Simon Glass <sjg at chromium.org> wrote:
>>>
>>> Hi Bin,
>>>
>>>
>>> On 27 September 2016 at 19:23, Bin Meng <bmeng.cn at gmail.com> wrote:
>>>
>>> Hi Simon,
>>>
>>>
>>> On Wed, Sep 28, 2016 at 1:55 AM, Simon Glass <sjg at chromium.org> wrote:
>>>
>>> Hi Bin,
>>>
>>>
>>> On 26 September 2016 at 20:44, Bin Meng <bmeng.cn at gmail.com> wrote:
>>>
>>> Hi Simon,
>>>
>>>
>>> On Tue, Sep 27, 2016 at 8:35 AM, Simon Glass <sjg at chromium.org> wrote:
>>>
>>> Hi Bin,
>>>
>>>
>>> On 26 September 2016 at 02:50, Bin Meng <bmeng.cn at gmail.com> wrote:
>>>
>>> Hi Simon,
>>>
>>>
>>> On Mon, Sep 26, 2016 at 5:27 AM, Simon Glass <sjg at chromium.org> wrote:
>>>
>>> At present we use a CONFIG option in efi.h to determine whether we are
>>>
>>> building the EFI stub or not. This means that the same header cannot be
>>>
>>> used for EFI_LOADER support. The CONFIG option will be enabled for the
>>>
>>> whole build, even when not building the stub.
>>>
>>>
>>> Use a different define instead, set up just for the files that make up
>>> the
>>>
>>> stub.
>>>
>>>
>>> Signed-off-by: Simon Glass <sjg at chromium.org>
>>>
>>> ---
>>>
>>>
>>> Changes in v2:
>>>
>>> - Add new patch to tidy up selection of building the EFI stub
>>>
>>>
>>> include/efi.h    | 7 +++++--
>>>
>>> lib/efi/Makefile | 4 ++--
>>>
>>> 2 files changed, 7 insertions(+), 4 deletions(-)
>>>
>>>
>>> diff --git a/include/efi.h b/include/efi.h
>>>
>>> index d07187c..3d58780 100644
>>>
>>> --- a/include/efi.h
>>>
>>> +++ b/include/efi.h
>>>
>>> @@ -30,8 +30,11 @@ struct efi_device_path;
>>>
>>>
>>> #define EFI_BITS_PER_LONG      BITS_PER_LONG
>>>
>>>
>>> -/* With 64-bit EFI stub, EFI_BITS_PER_LONG has to be 64 */
>>>
>>> -#ifdef CONFIG_EFI_STUB_64BIT
>>>
>>> +/*
>>>
>>> + * With 64-bit EFI stub, EFI_BITS_PER_LONG has to be 64. EFI_STUB is set
>>>
>>> + * in lib/efi/Makefile, when building the stub.
>>>
>>> + */
>>>
>>> +#if defined(CONFIG_EFI_STUB_64BIT) && defined(EFI_STUB)
>>>
>>>
>>> I don't understand why this is needed?
>>>
>>>
>>> If building the 64-bit EFI stub, we need to use 64-bit ints for the
>>>
>>> stub, but 32-bits for the rest of U-Boot. So this header gets used
>>>
>>> both ways.
>>>
>>>
>>>
>>> For 32-bit EFI stub or U-Boot itself, EFI_BITS_PER_LONG is defined as
>>>
>>> BITS_PER_LONG which is 32.
>>>
>>>
>>> Yes that's right. But in the case of the stub, it can be different
>>>
>>> from U-Boot itself. This case takes care of that.
>>>
>>>
>>>
>>> Sorry but I still don't get it. What's broken without this change?
>>>
>>>
>>> When building U-Boot with CONFIG_EFI_STUB_64BIT enabled, at present
>>>
>>> EFI_BITS_PER_LONG will be 64.
>>>
>>>
>>> This is fine for building the stub.
>>>
>>>
>>>
>>> Yes
>>>
>>> But for building U-Boot, we still want it to be 32.
>>>
>>>
>>>
>>> Yes
>>>
>>> At present the code overrides EFI_BITS_PER_LONG, setting it to 64 if
>>>
>>> CONFIG_EFI_STUB_64BIT is enabled.
>>>
>>>
>>> This means that EFI_LOADER support does not build properly, since it
>>>
>>> uses 64 instead of 32.
>>>
>>>
>>>
>>> So you want CONFIG_EFI_STUB_64BIT and CONFIG_EFI_LOADER both be
>>> defined? I don't think it is a valid configuration.
>>>
>>>
>>> Why not?
>>>
>> So the board has a 64-bit UEFI BIOS, and with CONFIG_EFI_STUB_64BIT we
>> build U-Boot as a 64-bit UEFI payload and let the UEFI BIOS boot the
>> payload (U-Boot), then with CONFIG_EFI_LOADER we are trying to provide
>> the UEFI runtime environment within the U-Boot. What value are we
>> looking for? This is asking for troubles.
>
>
> Why is this asking for trouble? The inner uefi payload has no idea that the
> outer uefi firmware exists. It only ever talks to u-boot. I would argue the
> other way around: If we can't make it work, we have a layering problem.
>

This shows no value to me. In the end, providing EFI loader in the
U-Boot is to load some EFI apps. But this can be done from the
original UEFI BIOS without the need to have the middle-stage U-Boot
payload. What layering problem do we want to fix here? Are you saying
testing EFI loader in the U-Boot is not enough, so that we should
support such configuration for additional testing?

Regards,
Bin