[U-Boot] [PATCH 3/4] x86: doc: Mention qemu-x86_64 support

[Heinrich Schuchardt]

On 10/11/2018 05:27 PM, Bin Meng wrote:
> Hi Heinrich,
> 
> On Thu, Oct 11, 2018 at 11:15 PM Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>>
>> On 10/11/2018 03:53 AM, Bin Meng wrote:
>>> Currently only 32-bit U-Boot for QEMU x86 is documented. Mention
>>> the 64-bit support.
>>>
>>> Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
>>> ---
>>>
>>>  doc/README.x86 | 8 ++++++--
>>>  1 file changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/doc/README.x86 b/doc/README.x86
>>> index 8cc4672..ab48466 100644
>>> --- a/doc/README.x86
>>> +++ b/doc/README.x86
>>> @@ -32,7 +32,7 @@ are supported:
>>>     - Link (Chromebook Pixel)
>>>     - Minnowboard MAX
>>>     - Samus (Chromebook Pixel 2015)
>>> -   - QEMU x86
>>> +   - QEMU x86 (32-bit & 64-bit)
>>>
>>>  As for loading an OS, U-Boot supports directly booting a 32-bit or 64-bit
>>>  Linux kernel as part of a FIT image. It also supports a compressed zImage.
>>> @@ -376,7 +376,9 @@ QEMU x86 target instructions for bare mode:
>>>
>>>  To build u-boot.rom for QEMU x86 targets, just simply run
>>>
>>> -$ make qemu-x86_defconfig
>>> +$ make qemu-x86_defconfig (for 32-bit)
>>> +or
>>> +$ make qemu-x86_64_defconfig (for 64-bit)
>>>  $ make all
>>
>> If your patch series creates a U-Boot usable with QEMU depends on the
>> chosen CPU:
>>
>> This one seems to work:
>> qemu-system-x86_64 -bios u-boot.rom -nographic -cpu core2duo
>>
>> This one fails (as expected):
>> qemu-system-x86_64 -bios u-boot.rom --nographic -cpu pentium
> 
> Pentium does not support 64-bit, so it is expected. In my testing I
> always omit the '-cpu' so this is not a problem. But I can document
> this.
> 
>>
>> I could not get the emulation running without -nographic. Do you know why?
>>
> 
> This is due to currently the VGA support is missing in the 64-bit U-Boot.
> 
>> The documentation above is insufficient. Please, provide a minimum QEMU
>> command line which includes a CPU specification.
>>
>> I would prefer if you could specify two lines per bitness - one with kvm
>> and one without, e.g.
> 
> I doubt -enable-kvm works with U-Boot.

Why? It is just an instruction how QEMU should emulate the CPU. KVM does
not require anything on the target software side.

I have had no problem with KVM on the i386 target.

Regards

Heinrich

> 
>>
>> qemu-system-x86_64 -bios u-boot.rom -nographic -enable-kvm -cpu host
>> qemu-system-x86_64 -bios u-boot.rom -nographic -cpu core2duo
>>
>> qemu-system-i386 -bios u-boot.rom -nographic -enable-kvm -cpu host
>> qemu-system-i386 -bios u-boot.rom -nographic -cpu core2duo
>>
> 
> Will add more info in v2.
> 
> Regards,
> Bin
>