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

[Markus Armbruster]

Jordan Justen <address@hidden> writes:

> On Tue, Nov 26, 2013 at 5:32 AM, Laszlo Ersek <address@hidden> wrote:
>> On 11/26/13 13:36, Markus Armbruster wrote:
>>
>>> Your stated purpose for multiple -pflash:
>>>
>>>     This accommodates the following use case: suppose that OVMF is split in
>>>     two parts, a writeable host file for non-volatile variable storage, and 
>>> a
>>>     read-only part for bootstrap and decompressible executable code.
>>>
>>> Such a split between writable part and read-only part makes sense to me.
>>> How is it done in physical hardware?  Single device with configurable
>>> write-protect, or two separate devices?
>>
>> (Jordan could help more.)
>>
>> Likely one device that's fully writeable.
>
> Most parts will have a dedicated read-only line.
>
> Many devices have 'block-locking' that will make some subset of blocks
> read-only until a reset.
>
> In addition to this, many chipsets will allow flash writes to be
> protected by triggering SMM when a flash write occurs.
>
> Using multiple chips are less common due to cost, but this is not a
> factor for QEMU. :)

Should we stick to what real hardware does?  Single device, perhaps with
block locking.