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

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Message-ID: <20190410124114-mutt-send-email-mst@kernel.org>
Date:   Wed, 10 Apr 2019 12:46:12 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Cornelia Huck <cohuck@...hat.com>
Cc:     Pankaj Gupta <pagupta@...hat.com>, jack@...e.cz,
        kvm@...r.kernel.org, david@...hat.com, jasowang@...hat.com,
        david@...morbit.com, qemu-devel@...gnu.org,
        virtualization@...ts.linux-foundation.org,
        adilger kernel <adilger.kernel@...ger.ca>, zwisler@...nel.org,
        aarcange@...hat.com, dave jiang <dave.jiang@...el.com>,
        linux-nvdimm@...ts.01.org,
        vishal l verma <vishal.l.verma@...el.com>,
        willy@...radead.org, hch@...radead.org, linux-acpi@...r.kernel.org,
        jmoyer@...hat.com, linux-ext4@...r.kernel.org, lenb@...nel.org,
        kilobyte@...band.pl, riel@...riel.com,
        yuval shaia <yuval.shaia@...cle.com>, stefanha@...hat.com,
        pbonzini@...hat.com, dan j williams <dan.j.williams@...el.com>,
        lcapitulino@...hat.com, kwolf@...hat.com, nilal@...hat.com,
        tytso@....edu, xiaoguangrong eric <xiaoguangrong.eric@...il.com>,
        darrick wong <darrick.wong@...cle.com>, rjw@...ysocki.net,
        linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, imammedo@...hat.com
Subject: Re: [Qemu-devel] [PATCH v5 2/5] virtio-pmem: Add virtio pmem driver

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@...hat.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@...hat.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