Re: [Qemu-devel] [PATCH 2/9 V5] hostmem-file: add the 'pmem' option

[Junyan He]

Because we have disk backend imitation for NVDimm kind memory, I think it is 
more

flexible for user to specify the real or not real pmem rather than we check in 
qemu

using the pmem_is_pmem API

________________________________
From: Stefan Hajnoczi <address@hidden>
Sent: Thursday, May 31, 2018 1:09:42 PM
To: address@hidden
Cc: address@hidden; Haozhong Zhang; address@hidden; address@hidden; 
address@hidden; address@hidden; address@hidden; address@hidden; Junyan He; 
address@hidden; address@hidden; address@hidden; address@hidden
Subject: Re: [Qemu-devel] [PATCH 2/9 V5] hostmem-file: add the 'pmem' option

On Thu, May 10, 2018 at 10:08:51AM +0800, address@hidden wrote:
> From: Junyan He <address@hidden>
>
> When QEMU emulates vNVDIMM labels and migrates vNVDIMM devices, it
> needs to know whether the backend storage is a real persistent memory,
> in order to decide whether special operations should be performed to
> ensure the data persistence.
>
> This boolean option 'pmem' allows users to specify whether the backend
> storage of memory-backend-file is a real persistent memory. If
> 'pmem=on', QEMU will set the flag RAM_PMEM in the RAM block of the
> corresponding memory region.

I'm still not sure if this option is necessary since pmem_is_pmem() is
available with the introduction of the libpmem dependency.  Why can't it
be used?

Stefan