From: Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
To: Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Cc: Kevin Wolf <kwolf-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Nitesh Narayan Lal
<nilal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>,
Xiao Guangrong
<xiaoguangrong.eric-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
KVM list <kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Rik van Riel <riel-ebMLmSuQjDVBDgjK7y7TUQ@public.gmane.org>,
linux-nvdimm
<linux-nvdimm-y27Ovi1pjclAfugRpC6u6w@public.gmane.org>,
David Hildenbrand <david-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Linux Kernel Mailing List
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Qemu Developers
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Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
Igor Mammedov <imammedo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Paolo Bonzini <pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
"Michael S. Tsirkin"
<mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Stefan Hajnoczi
<stefanha-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
zwisler-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
lcapitulino-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org
Subject: Re: [Qemu-devel] [PATCH v2 2/2] virtio-pmem: Add virtio pmem driver
Date: Wed, 17 Oct 2018 15:11:49 -0400 (EDT) [thread overview]
Message-ID: <431127218.21694133.1539803509205.JavaMail.zimbra@redhat.com> (raw)
In-Reply-To: <CAPcyv4hroaVWA-HgjWCnr7QTd_y7U8sCvS+Up733ttnD6_cKzQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
> On Fri, Oct 12, 2018 at 10:01 PM Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> 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.
>
> Before we can move forward with this driver we need additional
> filesystem enabling to detect when the backing device is fronting DAX
> pmem or a paravirtualized page cache through virtio-pmem. Any
> interface that requires fsync() and a round trip to the hypervisor to
> flush host page cache is not DAX.
I saw your proposal[1] for new mmap flag MAP_DIRECT. IIUIC mapping should fail for
MAP_DIRECT if it requires explicit flush or buffer indirection. So, if we disable
MAP_SYNC flag for virtio-pmem this should fail MAP_DIRECT as well? Otherwise
without MAP_DIRECT, virtio-pmem should be defaulted to VIRTIO flush mechanism.
[1] https://marc.info/?l=linux-fsdevel&m=153953206330814&w=2
Thanks,
Pankaj
next prev parent reply other threads:[~2018-10-17 19:11 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-13 5:00 [PATCH v2 0/2] kvm "fake DAX" device Pankaj Gupta
[not found] ` <20181013050021.11962-1-pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-10-13 5:00 ` [PATCH v2 1/2] libnvdimm: nd_region flush callback support Pankaj Gupta
2018-10-13 8:31 ` kbuild test robot
[not found] ` <20181013050021.11962-2-pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-10-13 9:38 ` kbuild test robot
2018-10-13 16:06 ` [PATCH v2 0/2] kvm "fake DAX" device Dan Williams
2018-10-13 16:29 ` [Qemu-devel] " Pankaj Gupta
2018-10-13 5:00 ` [PATCH v2 2/2] virtio-pmem: Add virtio pmem driver Pankaj Gupta
[not found] ` <20181013050021.11962-3-pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-10-13 16:10 ` Dan Williams
[not found] ` <CAPcyv4hroaVWA-HgjWCnr7QTd_y7U8sCvS+Up733ttnD6_cKzQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-10-17 19:11 ` Pankaj Gupta [this message]
2018-10-17 19:36 ` [Qemu-devel] " Dan Williams
2018-10-18 1:44 ` Pankaj Gupta
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