Re: [Qemu-devel] [PATCH v5 2/5] virtio-pmem: Add virtio pmem driver

From: "Michael S. Tsirkin" <mst@redhat.com>
To: Cornelia Huck <cohuck@redhat.com>
Cc: Pankaj Gupta <pagupta@redhat.com>,
	jack@suse.cz, kvm@vger.kernel.org, david@fromorbit.com,
	qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org,
	adilger kernel <adilger.kernel@dilger.ca>,
	zwisler@kernel.org, aarcange@redhat.com,
	dave jiang <dave.jiang@intel.com>,
	linux-nvdimm@lists.01.org,
	vishal l verma <vishal.l.verma@intel.com>,
	willy@infradead.org, hch@infradead.org,
	linux-acpi@vger.kernel.org, jmoyer@redhat.com,
	linux-ext4@vger.kernel.org, lenb@kernel.org, kilobyte@angband.pl,
	riel@surriel.com, yuval shaia <yuval.shaia@oracle.com>,
	stefanha@redhat.com, imammedo@redhat.com,
	dan j williams <dan.j.williams@intel.com>,
	lcapitulino@redhat.com, nilal@redhat.com, tytso@mit.edu,
	xiaoguangrong eric <xiaoguangrong.eric@gmail.com>,
	darrick wong <darrick.wong@oracle.com>,
	rjw@rjwysocki.net, linux-kernel@vger.kernel.org,
	linux-xfs@vger.kernel.org, linux-fsdevel@vg
Subject: Re: [Qemu-devel] [PATCH v5 2/5] virtio-pmem: Add virtio pmem driver
Date: Wed, 10 Apr 2019 12:46:12 -0400	[thread overview]
Message-ID: <20190410124114-mutt-send-email-mst__25048.9573505305$1554914810$gmane$org@kernel.org> (raw)
In-Reply-To: <20190410163139.4a04175e.cohuck@redhat.com>

On Wed, Apr 10, 2019 at 04:31:39PM +0200, Cornelia Huck wrote:
> On Wed, 10 Apr 2019 10:03:01 -0400 (EDT)
> Pankaj Gupta <pagupta@redhat.com> wrote:
> 
> > > 
> > > On Wed, Apr 10, 2019 at 09:38:22AM +0530, Pankaj Gupta wrote:  
> > > > This patch adds virtio-pmem driver for KVM guest.
> > > > 
> > > > Guest reads the persistent memory range information from
> > > > Qemu over VIRTIO and registers it on nvdimm_bus. It also
> > > > creates a nd_region object with the persistent memory
> > > > range information so that existing 'nvdimm/pmem' driver
> > > > can reserve this into system memory map. This way
> > > > 'virtio-pmem' driver uses existing functionality of pmem
> > > > driver to register persistent memory compatible for DAX
> > > > capable filesystems.
> > > > 
> > > > This also provides function to perform guest flush over
> > > > VIRTIO from 'pmem' driver when userspace performs flush
> > > > on DAX memory range.
> > > > 
> > > > Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> 
> > > > diff --git a/include/uapi/linux/virtio_ids.h
> > > > b/include/uapi/linux/virtio_ids.h
> > > > index 6d5c3b2d4f4d..346389565ac1 100644
> > > > --- a/include/uapi/linux/virtio_ids.h
> > > > +++ b/include/uapi/linux/virtio_ids.h
> > > > @@ -43,5 +43,6 @@
> > > >  #define VIRTIO_ID_INPUT        18 /* virtio input */
> > > >  #define VIRTIO_ID_VSOCK        19 /* virtio vsock transport */
> > > >  #define VIRTIO_ID_CRYPTO       20 /* virtio crypto */
> > > > +#define VIRTIO_ID_PMEM         25 /* virtio pmem */
> > > >  
> > > >  #endif /* _LINUX_VIRTIO_IDS_H */  
> > > 
> > > Didn't Paolo point out someone is using 25 for audio?  
> > 
> > 
> > Sorry! I did not notice this.
> > 
> > > 
> > > Please, reserve an ID with the Virtio TC before using it.  
> > 
> > I thought I requested[1] ID 25.
> > 
> > [1] https://github.com/oasis-tcs/virtio-spec/issues/38
> > [2] https://lists.oasis-open.org/archives/virtio-dev/201805/threads.html
> > 
> > In that case I will send request for next available ID i.e 26?
> 
> Have the folks using this for audio sent a reservation request as well?
> If not, I'd say the first requester should get the id...

No but I think they ship their's already. No one ships pmem
so it's less pain for everyone if we just skip 25.

> (And yes, we need to be quicker with voting on/applying id
> reservations :/)

We can't vote on what was not proposed for a vote.
At the moment that responsibility is with the commented
once discussion on the comment has taken place.

I think what's missing is a description of the process
in the README. Want to write it up and post it?

-- 
MST