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

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 9/21/20 2:24 PM, Dr. David Alan Gilbert wrote:
> * 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.

My worry is TYPE_PCI_SDHCI ("sdhci-pci"):

    k->vendor_id = PCI_VENDOR_ID_REDHAT;
    k->device_id = PCI_DEVICE_ID_REDHAT_SDHCI;
    k->class_id = PCI_CLASS_SYSTEM_SDHCI;

config SDHCI_PCI
    bool
    default y if PCI_DEVICES

> 
> 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.