Re: [Qemu-devel] Testing sysbus devices

[Markus Armbruster <armbru@redhat.com>]

Stephen Checkoway <stephen.checkoway@oberlin.edu> writes:

>> On Feb 19, 2019, at 10:28, Markus Armbruster <armbru@redhat.com> wrote:
>> 
>> My terminology might be confused...
>> 
>> Let me backtrack a bit an explain my use case.  On physical PCs, the
>> single flash chip is commonly configured to have a read-only part and a
>> read/write part.  The read-only part holds UEFI code, and the read-write
>> part holds its persistent state.
>> 
>> Since our virtual flash chips lack this feature, our virtual PCs have
>> *two* of them: one configured read-only, and one configured read/write.
>> Cleaning that up would be nice.
>> 
>> The comment "It does not implement software data protection as found in
>> many real chips" in both pflash_cfi0*.c might be referring to this
>> missing feature.
>
> I understand now, thank you for explaining. I noticed the comments about software data protection in the code, but I didn't investigate.
>
>>From a quick look at <https://www.cypress.com/file/195291/download> Table 27 on page 8, I see there are at least 4 different protection modes. I think the most common one (based on my reading of a handful of data sheets for flash chips) is the high voltage one. Essentially, there are sector groups that can be locked/unlocked using high voltage. It seems easy enough to model this by configuring sectors as locked and refusing to erase or program them.
>
> Software command locking would probably involve implementing a few additional commands.
>
> I'm not sure what the others are.
>
> Which locking method do you need?

László, Philippe, what would you prefer to work with in OVMF?