lkml.org 
[lkml]   [2017]   [Oct]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [Qemu-devel] [RFC 2/2] KVM: add virtio-pmem driver
On Tue, Oct 17, 2017 at 04:30:41AM -0400, Pankaj Gupta wrote:
>
> > > Are you saying do it as existing i.e ACPI pmem like interface?
> > > The reason we have created this new driver is exiting pmem driver
> > > does not define proper semantics for guest flushing requests.
> >
> > At this point I'm caring about the Linux-internal interface, and
> > for that it should be integrated into the nvdimm subsystem and not
> > a block driver. How the host <-> guest interface looks is a different
> > idea.
> >
> > >
> > > Regarding block support of driver, we want to achieve DAX support
> > > to bypass guest page cache. Also, we want to utilize existing DAX
> > > capable file-system interfaces(e.g fsync) from userspace file API's
> > > to trigger the host side flush request.
> >
> > Well, if you want to support XFS+DAX better don't make it a block
> > devices, because I'll post patches soon to stop using the block device
> > entirely for the DAX case.
>
> o.k I will look at your patches once they are in mailing list.
> Thanks for the heads up.
>
> If I am guessing it right, we don't need block device additional features
> for pmem? We can bypass block device features like blk device cache flush etc.
> Also, still we would be supporting ext4 & XFS filesystem with pmem?
>
> If there is time to your patches can you please elaborate on this a bit.

I think the idea is that the nvdimm subsystem already adds block device
semantics on top of the struct nvdimms that it manages. See
drivers/nvdimm/blk.c.

So it would be cleaner to make virtio-pmem an nvdimm bus. This will
eliminate the duplication between your driver and drivers/nvdimm/ code.
Try "git grep nvdimm_bus_register" to find drivers that use the nvdimm
subsystem.

The virtio-pmem driver could register itself similar to the existing
ACPI NFIT and BIOS e820 pmem drivers.

Stefan

\
 
 \ /
  Last update: 2017-10-22 17:13    [W:0.084 / U:0.004 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site