[PATCH v3] powerpc/papr_scm: Implement support for H_SCM_FLUSH hcall

[Aneesh Kumar K.V]

On 3/31/21 3:50 PM, Michael Ellerman wrote:
> "Aneesh Kumar K.V" <aneesh.kumar at linux.ibm.com> writes:
>> Shivaprasad G Bhat <sbhat at linux.ibm.com> writes:
>>
>>> Add support for ND_REGION_ASYNC capability if the device tree
>>> indicates 'ibm,hcall-flush-required' property in the NVDIMM node.
>>> Flush is done by issuing H_SCM_FLUSH hcall to the hypervisor.
>>>
>>> If the flush request failed, the hypervisor is expected to
>>> to reflect the problem in the subsequent nvdimm H_SCM_HEALTH call.
>>>
>>> This patch prevents mmap of namespaces with MAP_SYNC flag if the
>>> nvdimm requires an explicit flush[1].
>>>
>>> References:
>>> [1] https://github.com/avocado-framework-tests/avocado-misc-tests/blob/master/memory/ndctl.py.data/map_sync.c
>>
>>
>> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
> 
> Do we need an ack from nvdimm folks on this?
> 
> Or is it entirely powerpc internal (seems like it from the diffstat)?
> 

This is within powerpc and we are implementing details w.r.t PAPR spec. 
There is a Qemu implementation that is getting reviewed here
https://lore.kernel.org/linux-nvdimm/161650723087.2959.8703728357980727008.stgit@6532096d84d3

But with respect to this patch, we can take that independent of the Qemu 
backend implementation.

-aneesh