Re: [Qemu-devel] [edk2] [qemu PATCH] hw/i386/pc_sysfw: support more than one flash drive

[Paolo Bonzini]

Il 26/11/2013 14:53, Laszlo Ersek ha scritto:
>> > 
>> > IIUC in the case of OVMF the guest "just knows" that there are multiple
>> > devices backing the range.  Is that right?
> No, the guest (the flash driver) is unaware of that. It could know if it
> wanted to, but it doesn't care. It cares about a base address and a
> size, and that range is subdivided into various roles. But how many
> flash devices back the range is not interesting for the driver.
> 
> Jordan wrote the driver with one flash device in mind, and when I split
> the image in two parts, I took care to map them so that the base
> address, the size, and those boundaries stay the same. It's sufficient
> for the driver to continue working.

Ah, I see it now.  That's because the driver never needs to write an
offset into the flash device.  Offsets are communicated by writing to
different memory addresses.

Since the OVMF driver never queries the size of the device, it doesn't
care whether the flash is one or two.

Paolo