Re: [RFC PATCH 3/6] hw/sd/sdcard: Do not use legal address '0' for INVALID_ADDRESS

[Dr. David Alan Gilbert]

* Markus Armbruster (armbru@redhat.com) wrote:
> Philippe Mathieu-Daudé <philmd@redhat.com> writes:
> 
> > +Paolo & Kevin.
> >
> > On 9/21/20 10:40 AM, Markus Armbruster wrote:
> >> Philippe Mathieu-Daudé <f4bug@amsat.org> writes:
> >> 
> >>> As it is legal to WRITE/ERASE the address/block 0,
> >>> change the value of this definition to an illegal
> >>> address: UINT32_MAX.
> >>>
> >>> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> >>> ---
> >>> Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
> >>> Cc: Markus Armbruster <armbru@redhat.com>
> >>>
> >>> Same problem I had with the pflash device last year...
> >>> This break migration :(
> >>> What is the best way to do this?
> >> 
> >> Remind me: did we solve the problem with pflash, and if yes, how?
> >
> > No we can't. The best I could do is add a comment and as this
> > is not fixable. See commit aba53a12bd5: ("hw/block/pflash_cfi01:
> > Document use of non-CFI compliant command '0x00'").
> >
> > I now consider the device in maintenance-only
> > mode and won't add any new features.
> >
> > I started working on a new implementation, hoping it can be a
> > drop in replacement. Laszlo still has hope that QEMU pflash
> > device will support sector locking so firmware developers could
> > test upgrading fw in VMs.
> >
> > Back to the SDcard, it might be less critical, so a migration
> > breaking change might be acceptable. I'm only aware of Paolo
> > and Kevin using this device for testing. Not sure of its
> > importance in production.
> 
> Neither am I.
> 
> Which machine types include this device by default?

To me it looks like it's some of the ARM boards.

Dave

> How can a non-default device be added, and to which machine types?
> 
> I gather the fix changes device state incompatibly.  Always, or only in
> certain states?  I'm asking because if device state remains compatible
> most of the time, we might be able use subsection trickery to keep
> migration working most of the time.  Has been done before, I think.
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK