From: Dan Williams <dan.j.williams@intel.com>
To: Jason Gunthorpe <jgg@mellanox.com>
Cc: Christoph Hellwig <hch@infradead.org>,
linux-nvdimm <linux-nvdimm@lists.01.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Doug Ledford <dledford@redhat.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 09:10:06 -0700 [thread overview]
Message-ID: <CAPcyv4hSPWEUih=we5QM_rdk7fLemi8phyk8_0tOd8ieL_=vPg@mail.gmail.com> (raw)
In-Reply-To: <20200709153854.GY23821@mellanox.com>
On Thu, Jul 9, 2020 at 8:39 AM Jason Gunthorpe <jgg@mellanox.com> wrote:
>
> On Thu, Jul 09, 2020 at 04:00:51PM +0100, Christoph Hellwig wrote:
> > On Mon, Jul 06, 2020 at 06:59:32PM -0700, 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.
>
> Are you saying freeze doesn't work for some RDMA drivers? That would
> be a driver bug, I think.
Right, it's more my hunch than a known bug at this point, but in my
experience with testing server class hardware when I've reported a
power management bugs I've sometimes got the incredulous response "who
suspends / hibernates servers!?". I can drop that comment.
Are there protocol timeouts that might need to be adjusted for a 100s
of microseconds blip in memory controller response?
> The consequences of doing freeze are pretty serious, but it should
> still stop DMA.
Ok, and there is still the option to race the quiesce if the effects
of the freeze are worse than a potential timeout from the quiesce.
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next prev parent reply other threads:[~2020-07-09 16:10 UTC|newest]
Thread overview: 24+ 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
2020-07-10 14:02 ` Sasha Levin
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
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 [this message]
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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