From: Dan Williams <dan.j.williams@intel.com>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: linux-nvdimm <linux-nvdimm@lists.01.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Vishal Verma <vishal.l.verma@intel.com>,
Doug Ledford <dledford@redhat.com>,
Jason Gunthorpe <jgg@mellanox.com>,
Dave Jiang <dave.jiang@intel.com>,
Ira Weiny <ira.weiny@intel.com>, Pavel Machek <pavel@ucw.cz>,
Len Brown <len.brown@intel.com>,
Linux ACPI <linux-acpi@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 11/12] PM, libnvdimm: Add 'mem-quiet' state and callback for firmware activation
Date: Thu, 9 Jul 2020 12:04:30 -0700 [thread overview]
Message-ID: <CAPcyv4iiYMXO1fH0yQ2eBzpOWqPag0W=ebJwV6spGpNJQ9hnrg@mail.gmail.com> (raw)
In-Reply-To: <23449996.3uVv1d17cZ@kreacher>
On Thu, Jul 9, 2020 at 7:57 AM Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
>
> On Tuesday, July 7, 2020 3:59:32 AM CEST Dan Williams wrote:
> > The runtime firmware activation capability of Intel NVDIMM devices
> > requires memory transactions to be disabled for 100s of microseconds.
> > This timeout is large enough to cause in-flight DMA to fail and other
> > application detectable timeouts. Arrange for firmware activation to be
> > executed while the system is "quiesced", all processes and device-DMA
> > frozen.
> >
> > It is already required that invoking device ->freeze() callbacks is
> > sufficient to cease DMA. A device that continues memory writes outside
> > of user-direction violates expectations of the PM core to be to
> > establish a coherent hibernation image.
> >
> > That said, RDMA devices are an example of a device that access memory
> > outside of user process direction. RDMA drivers also typically assume
> > the system they are operating in will never be hibernated. A solution
> > for RDMA collisions with firmware activation is outside the scope of
> > this change and may need to rely on being able to survive the platform
> > imposed memory controller quiesce period.
>
> Thanks for following my suggestion to use the hibernation infrastructure
> rather than the suspend one, but I think it would be better to go a bit
> further with that.
>
> Namely, after thinking about this a bit more I have come to the conclusion
> that what is needed is an ability to execute a function, inside of the
> kernel, in a "quiet" environment in which memory updates are unlikely.
>
> While the hibernation infrastructure as is can be used for that, kind of, IMO
> it would be cleaner to introduce a helper for that, like in the (untested)
> patch below, so if the "quiet execution environment" is needed, whoever
> needs it may simply pass a function to hibernate_quiet_exec() and provide
> whatever user-space I/F is suitable on top of that.
>
> Please let me know what you think.
This looks good to me in concept.
Would you expect that I trigger this from libnvdimm sysfs, or any
future users of this functionality to trigger it through their own
subsystem specific mechanisms?
I have a place for it in libvdimm and could specify the activation
method directly as "suspend" vs "live" activation.
next prev parent reply other threads:[~2020-07-09 19:04 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-07 1:58 [PATCH v2 00/12] ACPI/NVDIMM: Runtime Firmware Activation Dan Williams
2020-07-07 1:58 ` [PATCH v2 01/12] libnvdimm: Validate command family indices Dan Williams
2020-07-07 1:58 ` [PATCH v2 02/12] ACPI: NFIT: Move bus_dsm_mask out of generic nvdimm_bus_descriptor Dan Williams
2020-07-07 1:58 ` [PATCH v2 03/12] ACPI: NFIT: Define runtime firmware activation commands Dan Williams
2020-07-07 1:58 ` [PATCH v2 04/12] tools/testing/nvdimm: Cleanup dimm index passing Dan Williams
2020-07-07 1:59 ` [PATCH v2 05/12] tools/testing/nvdimm: Add command debug messages Dan Williams
2020-07-07 1:59 ` [PATCH v2 06/12] tools/testing/nvdimm: Prepare nfit_ctl_test() for ND_CMD_CALL emulation Dan Williams
2020-07-07 1:59 ` [PATCH v2 07/12] tools/testing/nvdimm: Emulate firmware activation commands Dan Williams
2020-07-07 1:59 ` [PATCH v2 08/12] driver-core: Introduce DEVICE_ATTR_ADMIN_{RO,RW} Dan Williams
2020-07-07 1:59 ` [PATCH v2 09/12] libnvdimm: Convert to DEVICE_ATTR_ADMIN_RO() Dan Williams
2020-07-07 1:59 ` [PATCH v2 10/12] libnvdimm: Add runtime firmware activation sysfs interface Dan Williams
2020-07-07 1:59 ` [PATCH v2 11/12] PM, libnvdimm: Add 'mem-quiet' state and callback for firmware activation Dan Williams
2020-07-07 16:56 ` Pavel Machek
2020-07-09 14:57 ` Rafael J. Wysocki
2020-07-09 19:04 ` Dan Williams [this message]
2020-07-13 14:03 ` Rafael J. Wysocki
2020-07-09 15:00 ` Christoph Hellwig
2020-07-09 15:38 ` Jason Gunthorpe
2020-07-09 15:43 ` Rafael J. Wysocki
2020-07-09 16:10 ` Dan Williams
2020-07-09 16:34 ` Jason Gunthorpe
2020-07-09 15:56 ` Dan Williams
2020-07-07 1:59 ` [PATCH v2 12/12] ACPI: NFIT: Add runtime firmware activate support Dan Williams
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