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From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Jason Gunthorpe <jgg@mellanox.com>
Cc: Christoph Hellwig <hch@infradead.org>,
	"linux-nvdimm@lists.01.org" <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>,
	ACPI Devel Maling List <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 17:43:52 +0200	[thread overview]
Message-ID: <CAJZ5v0hW79nEe1P5YqNx0o0jHAMuPw-i02GY3TCvG_uFu48ETg@mail.gmail.com> (raw)
In-Reply-To: <20200709153854.GY23821@mellanox.com>

On Thu, Jul 9, 2020 at 5:39 PM 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.
>
> The consequences of doing freeze are pretty serious, but it should
> still stop DMA.

Yes, it should.  The "freeze" callbacks are expected to prevent any
DMA transfers from being carried out after they have been executed.

Thanks!
_______________________________________________
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WARNING: multiple messages have this Message-ID (diff)
From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Jason Gunthorpe <jgg@mellanox.com>
Cc: Christoph Hellwig <hch@infradead.org>,
	Dan Williams <dan.j.williams@intel.com>,
	"linux-nvdimm@lists.01.org" <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>,
	ACPI Devel Maling List <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 17:43:52 +0200	[thread overview]
Message-ID: <CAJZ5v0hW79nEe1P5YqNx0o0jHAMuPw-i02GY3TCvG_uFu48ETg@mail.gmail.com> (raw)
In-Reply-To: <20200709153854.GY23821@mellanox.com>

On Thu, Jul 9, 2020 at 5:39 PM 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.
>
> The consequences of doing freeze are pretty serious, but it should
> still stop DMA.

Yes, it should.  The "freeze" callbacks are expected to prevent any
DMA transfers from being carried out after they have been executed.

Thanks!

  reply	other threads:[~2020-07-09 15:44 UTC|newest]

Thread overview: 48+ 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 ` Dan Williams
2020-07-07  1:58 ` [PATCH v2 01/12] libnvdimm: Validate command family indices Dan Williams
2020-07-07  1:58   ` Dan Williams
2020-07-10 14:02   ` Sasha Levin
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   ` 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   ` Dan Williams
2020-07-07  1:58 ` [PATCH v2 04/12] tools/testing/nvdimm: Cleanup dimm index passing Dan Williams
2020-07-07  1:58   ` 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   ` 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   ` 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   ` 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   ` 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   ` 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   ` 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  1:59   ` Dan Williams
2020-07-07 16:56   ` Pavel Machek
2020-07-07 16:56     ` Pavel Machek
2020-07-09 14:57   ` Rafael J. Wysocki
2020-07-09 14:57     ` Rafael J. Wysocki
2020-07-09 19:04     ` Dan Williams
2020-07-09 19:04       ` Dan Williams
2020-07-13 14:03       ` Rafael J. Wysocki
2020-07-13 14:03         ` Rafael J. Wysocki
2020-07-09 15:00   ` Christoph Hellwig
2020-07-09 15:00     ` Christoph Hellwig
2020-07-09 15:38     ` Jason Gunthorpe
2020-07-09 15:38       ` Jason Gunthorpe
2020-07-09 15:43       ` Rafael J. Wysocki [this message]
2020-07-09 15:43         ` Rafael J. Wysocki
2020-07-09 16:10       ` Dan Williams
2020-07-09 16:10         ` Dan Williams
2020-07-09 16:34         ` Jason Gunthorpe
2020-07-09 16:34           ` Jason Gunthorpe
2020-07-09 15:56     ` Dan Williams
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
2020-07-07  1:59   ` Dan Williams

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