Re: [PATCH v2] hvmloader: flip "ACPI data" to "ACPI NVS" type for ACPI table region

[Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>]

On 16/10/2020 14:34, Sander Eikelenboom wrote:
> On 16/10/2020 08:34, Jan Beulich wrote:
>> On 16.10.2020 02:39, Igor Druzhinin wrote:
>>> ACPI specification contains statements describing memory marked with regular
>>> "ACPI data" type as reclaimable by the guest. Although the guest shouldn't
>>> really do it if it wants kexec or similar functionality to work, there
>>> could still be ambiguities in treating these regions as potentially regular
>>> RAM.
>>>
>>> One such example is SeaBIOS which currently reports "ACPI data" regions as
>>> RAM to the guest in its e801 call. Which it might have the right to do as 
>>> any
>>> user of this is expected to be ACPI unaware. But a QEMU bootloader later 
>>> seems
>>> to ignore that fact and is instead using e801 to find a place for initrd 
>>> which
>>> causes the tables to be erased. While arguably QEMU bootloader or SeaBIOS 
>>> need
>>> to be fixed / improved here, that is just one example of the potential 
>>> problems
>>> from using a reclaimable memory type.
>>>
>>> Flip the type to "ACPI NVS" which doesn't have this ambiguity in it and is
>>> described by the spec as non-reclaimable (so cannot ever be treated like 
>>> RAM).
>>>
>>> Signed-off-by: Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>
>>
>> Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
>>
>>
> 
> I don't see any stable and or fixes tags, but I assume this will go to
> the stable trees (which have (a backport of)
> 8efa46516c5f4cf185c8df179812c185d3c27eb6 in their staging branches) ?

Yes, this should go to the stable branches as well. I don't usually see Fixes:
tag being used on xen-devel (not sure if it's intentional or simply not
customary). It's also questionable whether it's a fix or a workaround for an
issue with compatibility.

Igor