Re: [Qemu-devel] [PATCH v4 6/7] Make the kernel image in the fw_cfg DMA interface bootable

[Laszlo Ersek <lersek@redhat.com>]

On 10/01/15 18:02, Kevin O'Connor wrote:
> On Thu, Oct 01, 2015 at 05:25:11PM +0200, Laszlo Ersek wrote:
>> On 10/01/15 14:16, Marc Marí wrote:
>>> Add an entry to the bootorder file with name "vmlinux".
>>> Give this entry more priority than the romfile.
>>>
>>> Signed-off-by: Marc Marí <markmb@redhat.com>
>>> ---
>>>  hw/i386/pc.c | 4 +++-
>>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
>>> index 81d93b4..c4c51f7 100644
>>> --- a/hw/i386/pc.c
>>> +++ b/hw/i386/pc.c
>>> @@ -1012,8 +1012,10 @@ static void load_linux(PCMachineState *pcms,
>>>      fw_cfg_add_bytes(fw_cfg, FW_CFG_SETUP_DATA, setup, setup_size);
>>>  
>>>      option_rom[nb_option_roms].name = "linuxboot.bin";
>>> -    option_rom[nb_option_roms].bootindex = 0;
>>> +    option_rom[nb_option_roms].bootindex = 1;
>>>      nb_option_roms++;
>>> +
>>> +    add_boot_device_path(0, NULL, "vmlinux");
>>>  }
>>>  
>>>  #define NE2000_NB_MAX 6
>>>
>>
>> Where does this idea come from?
>>
>> This will yet again break the invariant that the bootorder fw_cfg file
>> is a list of OpenFirmware device paths.
> 
> I believe it came from a discussion between myself and Marc, because I
> did not like the way Marc's original SeaBIOS patches overloaded the
> meaning of "genroms/linuxboot.bin" in the bootorder file.
> 
> [...]
>> Given that direct kernel boot is always expected to take priority over
>> anything else (which is ensured by this QEMU patch too), can
>> bootprio_find_vmlinux() in SeaBIOS just look at the same fw_cfg key
>> (0x0008)?
> 
> That's fine with me.  Marc - I think qemu_vmlinux_setup() in SeaBIOS
> with the following would work:
> 
> void qemu_vmlinux_setup(void)
> {
>     u32 kernel_size;
>     qemu_cfg_read_entry(&kernel_size, QEMU_CFG_KERNEL_SIZE, sizeof(kernel_size));
>     if (kernel_size)
>         boot_add_qemu_vmlinux("QEMU Kernel image", 0);
> }

Thank you, Kevin; that would be great!
Laszlo

> Marc, if you're okay with the above, you don't have to keep respinning
> patches - I can fix it up upon commit.
> 
> -Kevin
>