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From: "Elliott, Robert (Persistent Memory)" <elliott@hpe.com>
To: 'Ross Zwisler' <ross.zwisler@linux.intel.com>,
	Igor Mammedov <imammedo@redhat.com>,
	"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Cc: "Michael S . Tsirkin" <mst@redhat.com>,
	Eduardo Habkost <ehabkost@redhat.com>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	linux-nvdimm <linux-nvdimm@lists.01.org>
Subject: RE: [qemu PATCH v2 3/4] nvdimm, acpi: support NFIT platform capabilities
Date: Thu, 17 May 2018 22:06:37 +0000	[thread overview]
Message-ID: <AT5PR8401MB11697DD6A19AA3F499ACDDBAAB910@AT5PR8401MB1169.NAMPRD84.PROD.OUTLOOK.COM> (raw)
In-Reply-To: <20180517050024.20101-4-ross.zwisler@linux.intel.com>



> -----Original Message-----
> From: Linux-nvdimm [mailto:linux-nvdimm-bounces@lists.01.org] On Behalf Of
> Ross Zwisler
> Sent: Thursday, May 17, 2018 12:00 AM
> Subject: [qemu PATCH v2 3/4] nvdimm, acpi: support NFIT platform
> capabilities
> 
> Add a machine command line option to allow the user to control the
> Platform
> Capabilities Structure in the virtualized NFIT.  This Platform
> Capabilities
> Structure was added in ACPI 6.2 Errata A.
> 
...
> +Platform Capabilities
> +---------------------
> +
> +ACPI 6.2 Errata A added support for a new Platform Capabilities Structure
> +which allows the platform to communicate what features it supports
> related to
> +NVDIMM data durability.  Users can provide a capabilities value to a
> guest via
> +the optional "nvdimm-cap" machine command line option:
> +
> +    -machine pc,accel=kvm,nvdimm,nvdimm-cap=2
> +
> +As of ACPI 6.2 Errata A, the following values are valid for the bottom
> two
> +bits:
> +
> +2 - Memory Controller Flush to NVDIMM Durability on Power Loss Capable.
> +3 - CPU Cache Flush to NVDIMM Durability on Power Loss Capable.

It's a bit unclear that those are decimal values for the field, not 
bit numbers.

...
> -static GArray *nvdimm_build_device_structure(void)
> +/*
> + * ACPI 6.2 Errata A: 5.2.25.9 NVDIMM Platform Capabilities Structure
> + */
> +static void
> +nvdimm_build_structure_caps(GArray *structures, uint32_t capabilities)
> +{
> +    NvdimmNfitPlatformCaps *nfit_caps;
> +
> +    nfit_caps = acpi_data_push(structures, sizeof(*nfit_caps));
> +
> +    nfit_caps->type = cpu_to_le16(7 /* NVDIMM Platform Capabilities */);
> +    nfit_caps->length = cpu_to_le16(sizeof(*nfit_caps));
> +    nfit_caps->highest_cap = 2;
> +    nfit_caps->capabilities = cpu_to_le32(capabilities);

highest_cap needs to be set to a value that at least covers the highest 
bit set to 1 used in capabilities.

As capabilities bits are added, there are three different meanings:
* 1: bit within highest_cap range, platform is claiming the 1 meaning
* 0: bit within highest_cap range, platform is claiming the 0 meaning
* not reported: bit not within highest_cap range, so the platform's
  implementation of this feature is unknown. Not necessarily the same 
  as the 0 meaning.

So, there should be a way to specify a highest_cap value to convey that
some of the upper capabilities bits are valid and contain 0.

---
Robert Elliott, HPE Persistent Memory


_______________________________________________
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https://lists.01.org/mailman/listinfo/linux-nvdimm

  reply	other threads:[~2018-05-17 22:06 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-17  5:00 [qemu PATCH v2 0/4] support NFIT platform capabilities Ross Zwisler
2018-05-17  5:00 ` [qemu PATCH v2 1/4] nvdimm: fix typo in label-size definition Ross Zwisler
2018-05-17  5:00 ` [qemu PATCH v2 2/4] tests/.gitignore: add entry for generated file Ross Zwisler
2018-05-17  5:00 ` [qemu PATCH v2 3/4] nvdimm, acpi: support NFIT platform capabilities Ross Zwisler
2018-05-17 22:06   ` Elliott, Robert (Persistent Memory) [this message]
2018-05-18 15:23     ` Ross Zwisler
2018-05-18 16:37       ` Elliott, Robert (Persistent Memory)
2018-05-18 19:31         ` Ross Zwisler
2018-05-21 15:54         ` Ross Zwisler
2018-05-17  5:00 ` [qemu PATCH v2 4/4] ACPI testing: test " Ross Zwisler
2018-05-17  5:08 ` [Qemu-devel] [qemu PATCH v2 0/4] support " no-reply
2018-05-17 15:32   ` [qemu PATCH v3 3/4] nvdimm, acpi: " Ross Zwisler

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