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From: Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
To: Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Kevin Wolf <kwolf-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
	<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Qemu Developers
	<qemu-devel-qX2TKyscuCcdnm+yROfE0A@public.gmane.org>,
	Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
	Igor Mammedov <imammedo-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,
	Paolo Bonzini <pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Nitesh Narayan Lal
	<nilal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Eric Blake <eblake-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Subject: Re: [PATCH v2 2/2] virtio-pmem: Add virtio pmem driver
Date: Sat, 13 Oct 2018 09:10:13 -0700	[thread overview]
Message-ID: <CAPcyv4hroaVWA-HgjWCnr7QTd_y7U8sCvS+Up733ttnD6_cKzQ@mail.gmail.com> (raw)
In-Reply-To: <20181013050021.11962-3-pagupta-H+wXaHxf7aLQT0dZR+AlfA@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.

WARNING: multiple messages have this Message-ID (diff)
From: Dan Williams <dan.j.williams@intel.com>
To: Pankaj Gupta <pagupta@redhat.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	KVM list <kvm@vger.kernel.org>,
	Qemu Developers <qemu-devel@nongnu.org>,
	linux-nvdimm <linux-nvdimm@ml01.01.org>, Jan Kara <jack@suse.cz>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	Rik van Riel <riel@surriel.com>,
	Nitesh Narayan Lal <nilal@redhat.com>,
	Kevin Wolf <kwolf@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	zwisler@kernel.org, Vishal L Verma <vishal.l.verma@intel.com>,
	Dave Jiang <dave.jiang@intel.com>,
	David Hildenbrand <david@redhat.com>,
	Xiao Guangrong <xiaoguangrong.eric@gmail.com>,
	Christoph Hellwig <hch@infradead.org>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	lcapitulino@redhat.com, Igor Mammedov <imammedo@redhat.com>,
	Eric Blake <eblake@redhat.com>
Subject: Re: [PATCH v2 2/2] virtio-pmem: Add virtio pmem driver
Date: Sat, 13 Oct 2018 09:10:13 -0700	[thread overview]
Message-ID: <CAPcyv4hroaVWA-HgjWCnr7QTd_y7U8sCvS+Up733ttnD6_cKzQ@mail.gmail.com> (raw)
In-Reply-To: <20181013050021.11962-3-pagupta@redhat.com>

On Fri, Oct 12, 2018 at 10:01 PM Pankaj Gupta <pagupta@redhat.com> 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.

WARNING: multiple messages have this Message-ID (diff)
From: Dan Williams <dan.j.williams@intel.com>
To: Pankaj Gupta <pagupta@redhat.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	KVM list <kvm@vger.kernel.org>,
	Qemu Developers <qemu-devel@nongnu.org>,
	linux-nvdimm <linux-nvdimm@ml01.01.org>, Jan Kara <jack@suse.cz>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	Rik van Riel <riel@surriel.com>,
	Nitesh Narayan Lal <nilal@redhat.com>,
	Kevin Wolf <kwolf@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	zwisler@kernel.org, Vishal L Verma <vishal.l.verma@intel.com>,
	Dave Jiang <dave.jiang@intel.com>,
	David Hildenbrand <david@redhat.com>,
	Xiao Guangrong <xiaoguangrong.eric@gmail.com>,
	Christoph Hellwig <hch@infradead.org>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	lcapitulino@redhat.com, Igor Mammedov <imammedo@redhat.com>,
	Eric Blake <eblake@redhat.com>
Subject: Re: [Qemu-devel] [PATCH v2 2/2] virtio-pmem: Add virtio pmem driver
Date: Sat, 13 Oct 2018 09:10:13 -0700	[thread overview]
Message-ID: <CAPcyv4hroaVWA-HgjWCnr7QTd_y7U8sCvS+Up733ttnD6_cKzQ@mail.gmail.com> (raw)
In-Reply-To: <20181013050021.11962-3-pagupta@redhat.com>

On Fri, Oct 12, 2018 at 10:01 PM Pankaj Gupta <pagupta@redhat.com> 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.

  parent reply	other threads:[~2018-10-13 16:10 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-13  5:00 [PATCH v2 0/2] kvm "fake DAX" device Pankaj Gupta
2018-10-13  5:00 ` [Qemu-devel] " Pankaj Gupta
2018-10-13  5:00 ` 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  5:00     ` [Qemu-devel] " Pankaj Gupta
2018-10-13  5:00     ` Pankaj Gupta
2018-10-13  8:31     ` kbuild test robot
2018-10-13  8:31       ` [Qemu-devel] " kbuild test robot
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  9:38         ` [Qemu-devel] " kbuild test robot
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 16:06     ` [Qemu-devel] " Dan Williams
2018-10-13 16:06     ` 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
2018-10-13  5:00   ` [Qemu-devel] " Pankaj Gupta
     [not found]   ` <20181013050021.11962-3-pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-10-13 16:10     ` Dan Williams [this message]
2018-10-13 16:10       ` Dan Williams
2018-10-13 16:10       ` Dan Williams
     [not found]       ` <CAPcyv4hroaVWA-HgjWCnr7QTd_y7U8sCvS+Up733ttnD6_cKzQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-10-17 19:11         ` [Qemu-devel] " Pankaj Gupta
2018-10-17 19:11           ` Pankaj Gupta
2018-10-17 19:36           ` Dan Williams
2018-10-18  1:44             ` Pankaj Gupta

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