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From: Dan Williams <dan.j.williams@intel.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>,
	Shivaprasad G Bhat <sbhat@linux.ibm.com>,
	David Gibson <david@gibson.dropbear.id.au>,
	Greg Kurz <groug@kaod.org>,
	qemu-ppc@nongnu.org, Eduardo Habkost <ehabkost@redhat.com>,
	Marcel Apfelbaum <marcel.apfelbaum@gmail.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Igor Mammedov <imammedo@redhat.com>,
	Xiao Guangrong <xiaoguangrong.eric@gmail.com>,
	Peter Maydell <peter.maydell@linaro.org>,
	Eric Blake <eblake@redhat.com>,
	qemu-arm@nongnu.org, richard.henderson@linaro.org,
	Paolo Bonzini <pbonzini@redhat.com>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	Haozhong Zhang <haozhong.zhang@intel.com>,
	shameerali.kolothum.thodi@huawei.com, kwangwoo.lee@sk.com,
	Markus Armbruster <armbru@redhat.com>,
	Qemu Developers <qemu-devel@nongnu.org>,
	linux-nvdimm <linux-nvdimm@lists.01.org>,
	kvm-ppc@vger.kernel.org, shivaprasadbhat@gmail.com,
	bharata@linux.vnet.ibm.com
Subject: Re: [PATCH v4 0/3] nvdimm: Enable sync-dax property for nvdimm
Date: Tue, 4 May 2021 17:12:19 -0700	[thread overview]
Message-ID: <CAPcyv4hEhZoma=t=EtDXGr9r-i5K0GP01NU=jyDOmdp1YHn2rw@mail.gmail.com> (raw)
In-Reply-To: <023e584a-6110-4d17-7fec-ca715226f869@linux.ibm.com>

On Tue, May 4, 2021 at 2:03 AM Aneesh Kumar K.V
<aneesh.kumar@linux.ibm.com> wrote:
>
> On 5/4/21 11:13 AM, Pankaj Gupta wrote:
> ....
>
> >>
> >> What this patch series did was to express that property via a device
> >> tree node and guest driver enables a hypercall based flush mechanism to
> >> ensure persistence.
> >
> > Would VIRTIO (entirely asynchronous, no trap at host side) based
> > mechanism is better
> > than hyper-call based? Registering memory can be done any way. We
> > implemented virtio-pmem
> > flush mechanisms with below considerations:
> >
> > - Proper semantic for guest flush requests.
> > - Efficient mechanism for performance pov.
> >
>
> sure, virio-pmem can be used as an alternative.
>
> > I am just asking myself if we have platform agnostic mechanism already
> > there, maybe
> > we can extend it to suit our needs? Maybe I am missing some points here.
> >
>
> What is being attempted in this series is to indicate to the guest OS
> that the backing device/file used for emulated nvdimm device cannot
> guarantee the persistence via cpu cache flush instructions.

Right, the detail I am arguing is that it should be a device
description, not a backend file property. In other words this proposal
is advocating this:

-object memory-backend-file,id=mem1,share,sync-dax=$sync-dax,mem-path=$path
-device nvdimm,memdev=mem1

...and I am advocating for reusing or duplicating the virtio-pmem
model like this:

-object memory-backend-file,id=mem1,share,mem-path=$path
-device spapr-hcall,memdev=mem1

...because the interface to the guest is the device, not the
memory-backend-file.
_______________________________________________
Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org
To unsubscribe send an email to linux-nvdimm-leave@lists.01.org

WARNING: multiple messages have this Message-ID (diff)
From: Dan Williams <dan.j.williams@intel.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Peter Maydell <peter.maydell@linaro.org>,
	Shivaprasad G Bhat <sbhat@linux.ibm.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Qemu Developers <qemu-devel@nongnu.org>,
	linux-nvdimm <linux-nvdimm@lists.01.org>,
	Markus Armbruster <armbru@redhat.com>,
	bharata@linux.vnet.ibm.com,
	Haozhong Zhang <haozhong.zhang@intel.com>,
	Eduardo Habkost <ehabkost@redhat.com>,
	richard.henderson@linaro.org, Greg Kurz <groug@kaod.org>,
	kvm-ppc@vger.kernel.org, qemu-arm@nongnu.org,
	Stefan Hajnoczi <stefanha@redhat.com>,
	Igor Mammedov <imammedo@redhat.com>,
	kwangwoo.lee@sk.com, David Gibson <david@gibson.dropbear.id.au>,
	Pankaj Gupta <pankaj.gupta.linux@gmail.com>,
	Xiao Guangrong <xiaoguangrong.eric@gmail.com>,
	shameerali.kolothum.thodi@huawei.com, shivaprasadbhat@gmail.com,
	qemu-ppc@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH v4 0/3] nvdimm: Enable sync-dax property for nvdimm
Date: Tue, 4 May 2021 17:12:19 -0700	[thread overview]
Message-ID: <CAPcyv4hEhZoma=t=EtDXGr9r-i5K0GP01NU=jyDOmdp1YHn2rw@mail.gmail.com> (raw)
In-Reply-To: <023e584a-6110-4d17-7fec-ca715226f869@linux.ibm.com>

On Tue, May 4, 2021 at 2:03 AM Aneesh Kumar K.V
<aneesh.kumar@linux.ibm.com> wrote:
>
> On 5/4/21 11:13 AM, Pankaj Gupta wrote:
> ....
>
> >>
> >> What this patch series did was to express that property via a device
> >> tree node and guest driver enables a hypercall based flush mechanism to
> >> ensure persistence.
> >
> > Would VIRTIO (entirely asynchronous, no trap at host side) based
> > mechanism is better
> > than hyper-call based? Registering memory can be done any way. We
> > implemented virtio-pmem
> > flush mechanisms with below considerations:
> >
> > - Proper semantic for guest flush requests.
> > - Efficient mechanism for performance pov.
> >
>
> sure, virio-pmem can be used as an alternative.
>
> > I am just asking myself if we have platform agnostic mechanism already
> > there, maybe
> > we can extend it to suit our needs? Maybe I am missing some points here.
> >
>
> What is being attempted in this series is to indicate to the guest OS
> that the backing device/file used for emulated nvdimm device cannot
> guarantee the persistence via cpu cache flush instructions.

Right, the detail I am arguing is that it should be a device
description, not a backend file property. In other words this proposal
is advocating this:

-object memory-backend-file,id=mem1,share,sync-dax=$sync-dax,mem-path=$path
-device nvdimm,memdev=mem1

...and I am advocating for reusing or duplicating the virtio-pmem
model like this:

-object memory-backend-file,id=mem1,share,mem-path=$path
-device spapr-hcall,memdev=mem1

...because the interface to the guest is the device, not the
memory-backend-file.


WARNING: multiple messages have this Message-ID (diff)
From: Dan Williams <dan.j.williams@intel.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>,
	Shivaprasad G Bhat <sbhat@linux.ibm.com>,
	David Gibson <david@gibson.dropbear.id.au>,
	Greg Kurz <groug@kaod.org>,
	qemu-ppc@nongnu.org, Eduardo Habkost <ehabkost@redhat.com>,
	Marcel Apfelbaum <marcel.apfelbaum@gmail.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Igor Mammedov <imammedo@redhat.com>,
	Xiao Guangrong <xiaoguangrong.eric@gmail.com>,
	Peter Maydell <peter.maydell@linaro.org>,
	Eric Blake <eblake@redhat.com>,
	qemu-arm@nongnu.org, richard.henderson@linaro.org,
	Paolo Bonzini <pbonzini@redhat.com>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	Haozhong Zhang <haozhong.zhang@intel.com>,
	shameerali.kolothum.thodi@huawei.com, kwangwoo.lee@sk.com,
	Markus Armbruster <armbru@redhat.com>,
	Qemu Developers <qemu-devel@nongnu.org>,
	linux-nvdimm <linux-nvdimm@lists.01.org>,
	kvm-ppc@vger.kernel.org, shivaprasadbhat@gmail.com,
	bharata@linux.vnet.ibm.com
Subject: Re: [PATCH v4 0/3] nvdimm: Enable sync-dax property for nvdimm
Date: Wed, 05 May 2021 00:12:19 +0000	[thread overview]
Message-ID: <CAPcyv4hEhZoma=t=EtDXGr9r-i5K0GP01NU=jyDOmdp1YHn2rw@mail.gmail.com> (raw)
In-Reply-To: <023e584a-6110-4d17-7fec-ca715226f869@linux.ibm.com>

On Tue, May 4, 2021 at 2:03 AM Aneesh Kumar K.V
<aneesh.kumar@linux.ibm.com> wrote:
>
> On 5/4/21 11:13 AM, Pankaj Gupta wrote:
> ....
>
> >>
> >> What this patch series did was to express that property via a device
> >> tree node and guest driver enables a hypercall based flush mechanism to
> >> ensure persistence.
> >
> > Would VIRTIO (entirely asynchronous, no trap at host side) based
> > mechanism is better
> > than hyper-call based? Registering memory can be done any way. We
> > implemented virtio-pmem
> > flush mechanisms with below considerations:
> >
> > - Proper semantic for guest flush requests.
> > - Efficient mechanism for performance pov.
> >
>
> sure, virio-pmem can be used as an alternative.
>
> > I am just asking myself if we have platform agnostic mechanism already
> > there, maybe
> > we can extend it to suit our needs? Maybe I am missing some points here.
> >
>
> What is being attempted in this series is to indicate to the guest OS
> that the backing device/file used for emulated nvdimm device cannot
> guarantee the persistence via cpu cache flush instructions.

Right, the detail I am arguing is that it should be a device
description, not a backend file property. In other words this proposal
is advocating this:

-object memory-backend-file,id=mem1,share,sync-dax=$sync-dax,mem-path=$path
-device nvdimm,memdev=mem1

...and I am advocating for reusing or duplicating the virtio-pmem
model like this:

-object memory-backend-file,id=mem1,share,mem-path=$path
-device spapr-hcall,memdev=mem1

...because the interface to the guest is the device, not the
memory-backend-file.

  reply	other threads:[~2021-05-05  0:12 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-29  3:48 [PATCH v4 0/3] nvdimm: Enable sync-dax property for nvdimm Shivaprasad G Bhat
2021-04-29  3:48 ` Shivaprasad G Bhat
2021-04-29  3:48 ` Shivaprasad G Bhat
2021-04-29  3:48 ` [PATCH v4 1/3] spapr: nvdimm: Forward declare and move the definitions Shivaprasad G Bhat
2021-04-29  3:48   ` Shivaprasad G Bhat
2021-04-29  3:48   ` Shivaprasad G Bhat
2021-05-03 18:23   ` Eric Blake
2021-05-03 18:23     ` Eric Blake
2021-05-03 18:23     ` Eric Blake
2021-05-04  1:21     ` David Gibson
2021-05-04  1:21       ` David Gibson
2021-05-04  1:21       ` David Gibson
2021-04-29  3:48 ` [PATCH v4 2/3] spapr: nvdimm: Implement H_SCM_FLUSH hcall Shivaprasad G Bhat
2021-04-29  3:48   ` Shivaprasad G Bhat
2021-04-29  3:48   ` Shivaprasad G Bhat
2021-04-29  3:49 ` [PATCH v4 3/3] nvdimm: Enable sync-dax device property for nvdimm Shivaprasad G Bhat
2021-04-29  3:49   ` Shivaprasad G Bhat
2021-04-29  3:49   ` Shivaprasad G Bhat
2021-05-03 18:27   ` Eric Blake
2021-05-03 18:27     ` Eric Blake
2021-05-03 18:27     ` Eric Blake
2021-04-29 15:55 ` [PATCH v4 0/3] nvdimm: Enable sync-dax " Stefan Hajnoczi
2021-04-29 15:55   ` Stefan Hajnoczi
2021-04-29 15:55   ` Stefan Hajnoczi
2021-04-29 16:32   ` Aneesh Kumar K.V
2021-04-29 16:44     ` Aneesh Kumar K.V
2021-04-29 16:32     ` Aneesh Kumar K.V
2021-04-30  4:27     ` David Gibson
2021-04-30  4:27       ` David Gibson
2021-04-30  4:27       ` David Gibson
2021-04-30 15:08       ` Stefan Hajnoczi
2021-04-30 15:08         ` Stefan Hajnoczi
2021-04-30 15:08         ` Stefan Hajnoczi
2021-04-30 19:14 ` Dan Williams
2021-04-30 19:14   ` Dan Williams
2021-04-30 19:14   ` Dan Williams
2021-05-01 13:55   ` Aneesh Kumar K.V
2021-05-01 13:56     ` Aneesh Kumar K.V
2021-05-01 13:55     ` Aneesh Kumar K.V
2021-05-03 14:05   ` Shivaprasad G Bhat
2021-05-03 14:17     ` Shivaprasad G Bhat
2021-05-03 14:05     ` Shivaprasad G Bhat
2021-05-03 19:41     ` Dan Williams
2021-05-03 19:41       ` Dan Williams
2021-05-03 19:41       ` Dan Williams
2021-05-04  4:59       ` Aneesh Kumar K.V
2021-05-04  4:59         ` Aneesh Kumar K.V
2021-05-04  4:59         ` Aneesh Kumar K.V
2021-05-04  5:43         ` Pankaj Gupta
2021-05-04  5:43           ` Pankaj Gupta
2021-05-04  5:43           ` Pankaj Gupta
2021-05-04  9:02           ` Aneesh Kumar K.V
2021-05-04  9:14             ` Aneesh Kumar K.V
2021-05-04  9:02             ` Aneesh Kumar K.V
2021-05-05  0:12             ` Dan Williams [this message]
2021-05-05  0:12               ` Dan Williams
2021-05-05  0:12               ` Dan Williams

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