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From: Pankaj Gupta <pagupta@redhat.com>
To: Jeff Moyer <jmoyer@redhat.com>, Dan Williams <dan.j.williams@intel.com>
Cc: Jan Kara <jack@suse.cz>, KVM list <kvm@vger.kernel.org>,
	David Hildenbrand <david@redhat.com>,
	linux-nvdimm <linux-nvdimm@ml01.01.org>,
	Ross Zwisler <ross.zwisler@intel.com>,
	Qemu Developers <qemu-devel@nongnu.org>,
	lcapitulino@redhat.com, Linux MM <linux-mm@kvack.org>,
	niteshnarayanlal@hotmail.com,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Christoph Hellwig <hch@infradead.org>,
	Marcel Apfelbaum <marcel@redhat.com>,
	Nitesh Narayan Lal <nilal@redhat.com>,
	Haozhong Zhang <haozhong.zhang@intel.com>,
	Rik van Riel <riel@surriel.com>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Kevin Wolf <kwolf@redhat.com>,
	Xiao Guangrong <xiaoguangrong.eric@gmail.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Igor Mammedov <imammedo@redhat.com>
Subject: Re: [Qemu-devel] [RFC v2 1/2] virtio: add pmem driver
Date: Thu, 26 Apr 2018 13:15:38 -0400 (EDT)	[thread overview]
Message-ID: <1499190564.23017177.1524762938762.JavaMail.zimbra@redhat.com> (raw)
In-Reply-To: <x49o9i6885e.fsf@segfault.boston.devel.redhat.com>


> 
> Dan Williams <dan.j.williams@intel.com> writes:
> 
> > [ adding Jeff directly since he has also been looking at
> > infrastructure to track when MAP_SYNC should be disabled ]
> >
> > On Wed, Apr 25, 2018 at 7:21 AM, Dan Williams <dan.j.williams@intel.com>
> > wrote:
> >> On Wed, Apr 25, 2018 at 4:24 AM, Pankaj Gupta <pagupta@redhat.com> wrote:
> >>> This patch adds virtio-pmem driver for KVM
> >>> guest.
> >>
> >> Minor nit, please expand your changelog line wrapping to 72 columns.
> >>
> >>>
> >>> 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.
> >>
> >> We need some additional enabling to disable MAP_SYNC for this
> 
> enable to disable... I like it!  ;-)
> 
> >> configuration. In other words, if fsync() is required then we must
> >> disable the MAP_SYNC optimization. I think this should be a struct
> >> dax_device property looked up at mmap time in each MAP_SYNC capable
> >> ->mmap() file operation implementation.

I understand you mean we want to disable 'MAP_SYNC' optimization as
we are relying on additional fsync. You mean if we add a property/flag
in dax_device struct and its set, disable 'MAP_SYNC' accordingly during
mmap time for corresponding filesystems?  

> 
> Ideally, qemu (seabios?) would advertise a platform capabilities
> sub-table that doesn't fill in the flush bits.

Could you please elaborate on this, how its related to disabling
MAP_SYNC? We are not doing entire nvdimm device emulation. 

> 
> -Jeff
> 
> 

  reply	other threads:[~2018-04-26 17:15 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-25 11:24 [RFC v2 0/2] kvm "fake DAX" device flushing Pankaj Gupta
2018-04-25 11:24 ` [RFC v2 1/2] virtio: add pmem driver Pankaj Gupta
2018-04-25 14:21   ` Dan Williams
2018-04-25 14:43     ` Dan Williams
2018-04-26 12:27       ` Jeff Moyer
2018-04-26 17:15         ` Pankaj Gupta [this message]
2018-04-26 17:24           ` [Qemu-devel] " Jeff Moyer
2018-04-25 14:52   ` Michael S. Tsirkin
2018-04-25 15:11     ` [Qemu-devel] " Pankaj Gupta
2018-04-26 13:12   ` Stefan Hajnoczi
2018-04-26 15:44     ` Pankaj Gupta
2018-04-27 13:31       ` Stefan Hajnoczi
2018-04-28 10:48         ` Pankaj Gupta
2018-04-25 11:24 ` [RFC v2 2/2] pmem: device flush over VIRTIO Pankaj Gupta
2018-04-25 14:23   ` Dan Williams
2018-04-25 14:47     ` Pankaj Gupta
2018-04-26 13:15   ` Stefan Hajnoczi
2018-04-26 16:40     ` Pankaj Gupta
2018-04-26 16:57       ` Dan Williams
2018-04-26 17:13         ` Pankaj Gupta
2018-04-25 11:24 ` [RFC v2] qemu: Add virtio pmem device Pankaj Gupta
2018-04-25 11:35   ` [Qemu-devel] " no-reply
2018-04-25 11:58     ` Pankaj Gupta
2018-04-25 14:23       ` Eric Blake
2018-04-25 14:51         ` Pankaj Gupta
2018-04-25 11:46   ` no-reply
2018-04-25 14:25   ` Eric Blake
2018-04-25 14:55     ` Pankaj Gupta
2018-04-26 13:24   ` Stefan Hajnoczi
2018-04-26 16:43     ` [Qemu-devel] " Pankaj Gupta
2018-06-01 12:24 ` [Qemu-devel] [RFC v2 0/2] kvm "fake DAX" device flushing Igor Mammedov
2018-06-04  5:56   ` Pankaj Gupta
2018-06-04  9:55   ` David Hildenbrand

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