From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pankaj Gupta Subject: Re: [RFC 2/2] KVM: add virtio-pmem driver Date: Thu, 12 Oct 2017 18:18:39 -0400 (EDT) Message-ID: <1363955128.19944709.1507846719987.JavaMail.zimbra@redhat.com> References: <20171012155027.3277-1-pagupta@redhat.com> <20171012155027.3277-3-pagupta@redhat.com> <1567317495.19940236.1507843517318.JavaMail.zimbra@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Kevin Wolf , Rik van Riel , Jan Kara , Xiao Guangrong , KVM list , David Hildenbrand , linux-nvdimm , Ross Zwisler , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Qemu Developers , Linux MM , Stefan Hajnoczi , Paolo Bonzini , Nitesh Narayan Lal To: Dan Williams Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" List-Id: kvm.vger.kernel.org > > On Thu, Oct 12, 2017 at 2:25 PM, Pankaj Gupta wrote: > > > >> > This patch adds virtio-pmem driver for KVM guest. > >> > Guest reads the persistent memory range information > >> > over virtio bus from Qemu and reserves the range > >> > as persistent memory. Guest also allocates a block > >> > device corresponding to the pmem range which later > >> > can be accessed with DAX compatible file systems. > >> > Idea is to use the virtio channel between guest and > >> > host to perform the block device flush for guest pmem > >> > DAX device. > >> > > >> > There is work to do including DAX file system support > >> > and other advanced features. > >> > > >> > Signed-off-by: Pankaj Gupta > >> > --- > >> > drivers/virtio/Kconfig | 10 ++ > >> > drivers/virtio/Makefile | 1 + > >> > drivers/virtio/virtio_pmem.c | 322 > >> > +++++++++++++++++++++++++++++++++++++++ > >> > include/uapi/linux/virtio_pmem.h | 55 +++++++ > >> > 4 files changed, 388 insertions(+) > >> > create mode 100644 drivers/virtio/virtio_pmem.c > >> > create mode 100644 include/uapi/linux/virtio_pmem.h > >> > > >> > diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig > >> > index cff773f15b7e..0192c4bda54b 100644 > >> > --- a/drivers/virtio/Kconfig > >> > +++ b/drivers/virtio/Kconfig > >> > @@ -38,6 +38,16 @@ config VIRTIO_PCI_LEGACY > >> > > >> > If unsure, say Y. > >> > > >> > +config VIRTIO_PMEM > >> > + tristate "Virtio pmem driver" > >> > + depends on VIRTIO > >> > + ---help--- > >> > + This driver adds persistent memory range within a KVM guest. > >> > >> I think we need to call this something other than persistent memory to > >> make it clear that this not memory where the persistence can be > >> managed from userspace. The persistence point always requires a driver > >> call, so this is something distinctly different than "persistent > >> memory". For example, it's a bug if this memory range ends up backing > >> a device-dax range in the guest where there is no such thing as a > >> driver callback to perform the flushing. How does this solution > >> protect against that scenario? > > > > yes, you are right we are not providing device_dax in this case so it > > should > > be clear from name. Any suggestion for name? > > So currently /proc/iomem in a guest with a pmem device attached to a > namespace looks like this: > > c00000000-13bfffffff : Persistent Memory > c00000000-13bfffffff : namespace2.0 > > Can we call it "Virtio Shared Memory" to make it clear it is a > different beast than typical "Persistent Memory"? You can likely I think somewhere we need persistent keyword 'Virtio Persistent Memory' or so. > inject your own name into the resource tree the same way we do in the > NFIT driver. See acpi_nfit_insert_resource(). Sure! thank you.