Re: [Qemu-devel] [PATCH v7 0/2] PC system flash support

[Zhi Yong Wu]

On Sun, Nov 6, 2011 at 5:30 AM, Jordan Justen <address@hidden> wrote:
> Cc: qemu-devel
>
> On Fri, Nov 4, 2011 at 22:37, Zhi Yong Wu <address@hidden> wrote:
>> On Sat, Nov 5, 2011 at 12:11 AM, Jordan Justen <address@hidden> wrote:
>>> On Fri, Nov 4, 2011 at 04:34, Zhi Yong Wu <address@hidden> wrote:
>>>> BTW: what is the relationship between -bios and -pflash?
>>>
>>> Previously the QEMU/KVM PC system had no pflash support.  You could
>>> specify a pflash drive, but it would not appear in the VM.
>>>
>>> Also, previously the -bios flag would cause the specified binary to be
>>> loaded by QEMU, and then it was put into a memory region to be used
>>> for the firmware.
>>>
>>> After this change, the pflash drive is used for firmware.  So, it
>> This pflash drive is created with -pflash option, right?
>
> -pflash can be used, but I think it is just a short cut.
>
> -pflash /path/to/file
> is similar to:
> -drive if=pflash,file=/path/to/file
>
> And, after this change,
> -bios /path/to/file
> is similar to:
> -drive if=pflash,file=/path/to/file,readonly=on
>
>>> should be able to support qcow2, since qemu drives support the
>>> different formats.
>
> I confirmed that you can use a qcow2 image with -bios after this change.
>
>>> For backward compatibility, this change makes the -bios parameter be
>>> another way to specify the pflash drive.  If -bios is used, then a
>>> read-only pflash drive is created.
>> Sorry, i don't fully understand this. How about -bios and -pflash are
>> both specified.
>
> In this case the -pflash will be used, and -bios will be ignored.  I
> use -bios to create a pflash drive only if no pflash drive exists
> already.
>
> I think this should be okay, since -pflash has no use in the QEMU PC
> system before this patch, so it is unlikely that both -pflash and
> -bios will be used previously.
>
>>>> If your patch is applied to my source tree, can you know how to use 
>>>> -pflash?
>> Sorry, i made a mistake. I wanted to ask you how to use -pflash if
>> your patch is not applied.
>
> I don't think you can use pflash in a PC system when my patch is not
> applied.  I think without the patch qemu will create the pflash drive
> internally, but it will not be hooked to a device that the emulated PC
> system can see.
>
> I attached a log of me interacting with the pflash device under the
> EFI shell on OVMF *with* the patch applied.
>
Great, thanks a lot. Let me try next week.

> Thanks,
>
> -Jordan
>



-- 
Regards,

Zhi Yong Wu