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From: Dan Williams <dan.j.williams@intel.com>
To: Vishal Verma <vishal.l.verma@intel.com>
Cc: linux-cxl@vger.kernel.org, Ben Widawsky <ben.widawsky@intel.com>,
	Linux NVDIMM <nvdimm@lists.linux.dev>
Subject: Re: [ndctl PATCH v4 11/17] libcxl: add a stub interface to determine whether a memdev is active
Date: Thu, 14 Oct 2021 12:59:37 -0700	[thread overview]
Message-ID: <CAPcyv4hzozQnG-s1G_vf=Ej_sgOS+9=bRNbOn6v_fm_RiEdbMg@mail.gmail.com> (raw)
In-Reply-To: <20211007082139.3088615-12-vishal.l.verma@intel.com>

On Thu, Oct 7, 2021 at 1:22 AM Vishal Verma <vishal.l.verma@intel.com> wrote:
>
> Add an interface to determine whether a memdev is bound to a region
> driver and therefore is currently active.
>
> For now, this just returns '0' all the time - i.e. devices are always
> considered inactive. Flesh this out fully once the region driver is
> available.
>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
> ---
>  cxl/lib/libcxl.c   | 10 ++++++++++
>  cxl/libcxl.h       |  1 +
>  cxl/lib/libcxl.sym |  1 +
>  3 files changed, 12 insertions(+)
>
> diff --git a/cxl/lib/libcxl.c b/cxl/lib/libcxl.c
> index de3a8f7..59d091c 100644
> --- a/cxl/lib/libcxl.c
> +++ b/cxl/lib/libcxl.c
> @@ -362,6 +362,16 @@ CXL_EXPORT size_t cxl_memdev_get_label_size(struct cxl_memdev *memdev)
>         return memdev->lsa_size;
>  }
>
> +CXL_EXPORT int cxl_memdev_is_active(struct cxl_memdev *memdev)
> +{
> +       /*
> +        * TODO: Currently memdevs are always considered inactive. Once we have
> +        * cxl_bus drivers that are bound/unbound to memdevs, we'd use that to
> +        * determine the active/inactive state.
> +        */

So I jumped ahead to look at the use case for this and it brings up
questions if this is the right check for the label helpers to be
using. Note that the LSA commands may still be disabled even if the
memdev is inactive. This is because the NVDIMM bridge might be up and
have claimed the label operations for exclusive access via /dev/nmemX.

So perhaps this should become a narrower focused
cxl_memdev_label_area_active() or cxl_memdev_nvdimm_bridge_active().

I think Ben and I still need to arm wrestle how to mediate the label
area, but my going-in position is that the CXL subsystem works through
the NVDIMM subsystem to coordinate label updates. So
cxl_memdev_nvdimm_bridge_active() should be a sufficient check for
now. That's determined simply by the existence of a pmemX device as a
child of a memX device.


> +       return 0;
> +}
> +
>  CXL_EXPORT void cxl_cmd_unref(struct cxl_cmd *cmd)
>  {
>         if (!cmd)
> diff --git a/cxl/libcxl.h b/cxl/libcxl.h
> index d3b97a1..2e24371 100644
> --- a/cxl/libcxl.h
> +++ b/cxl/libcxl.h
> @@ -43,6 +43,7 @@ unsigned long long cxl_memdev_get_pmem_size(struct cxl_memdev *memdev);
>  unsigned long long cxl_memdev_get_ram_size(struct cxl_memdev *memdev);
>  const char *cxl_memdev_get_firmware_verison(struct cxl_memdev *memdev);
>  size_t cxl_memdev_get_label_size(struct cxl_memdev *memdev);
> +int cxl_memdev_is_active(struct cxl_memdev *memdev);
>
>  #define cxl_memdev_foreach(ctx, memdev) \
>          for (memdev = cxl_memdev_get_first(ctx); \
> diff --git a/cxl/lib/libcxl.sym b/cxl/lib/libcxl.sym
> index b9feb93..0e82030 100644
> --- a/cxl/lib/libcxl.sym
> +++ b/cxl/lib/libcxl.sym
> @@ -79,4 +79,5 @@ global:
>  LIBCXL_4 {
>  global:
>         cxl_memdev_get_label_size;
> +       cxl_memdev_is_active;
>  } LIBCXL_3;
> --
> 2.31.1
>

  reply	other threads:[~2021-10-14 19:59 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-07  8:21 [ndctl PATCH v4 00/17] Initial CXL support Vishal Verma
2021-10-07  8:21 ` [ndctl PATCH v4 01/17] ndctl: add .clang-format Vishal Verma
2021-10-07  8:21 ` [ndctl PATCH v4 02/17] cxl: add a cxl utility and libcxl library Vishal Verma
2021-10-07  8:21 ` [ndctl PATCH v4 03/17] cxl: add a local copy of the cxl_mem UAPI header Vishal Verma
2021-10-07  8:21 ` [ndctl PATCH v4 04/17] util: add the struct_size() helper from the kernel Vishal Verma
2021-10-14  2:40   ` Dan Williams
2021-10-07  8:21 ` [ndctl PATCH v4 05/17] libcxl: add support for command query and submission Vishal Verma
2021-10-14  2:53   ` Dan Williams
2021-10-07  8:21 ` [ndctl PATCH v4 06/17] libcxl: add support for the 'Identify Device' command Vishal Verma
2021-10-07  8:21 ` [ndctl PATCH v4 07/17] libcxl: add GET_HEALTH_INFO mailbox command and accessors Vishal Verma
2021-10-14 16:01   ` Dan Williams
2021-11-02 20:22     ` Verma, Vishal L
2021-11-02 20:27       ` Dan Williams
2021-10-07  8:21 ` [ndctl PATCH v4 08/17] libcxl: add support for the 'GET_LSA' command Vishal Verma
2021-10-14 16:35   ` Dan Williams
2021-10-14 20:06     ` Verma, Vishal L
2021-10-14 20:55       ` Dan Williams
2021-10-07  8:21 ` [ndctl PATCH v4 09/17] util/hexdump: Add a util helper to print a buffer in hex Vishal Verma
2021-10-14 16:48   ` Dan Williams
2021-10-14 20:33     ` Verma, Vishal L
2021-10-14 22:39       ` Dan Williams
2021-11-02 20:25         ` Verma, Vishal L
2021-10-07  8:21 ` [ndctl PATCH v4 10/17] libcxl: add label_size to cxl_memdev, and an API to retrieve it Vishal Verma
2021-10-14 18:24   ` Dan Williams
2021-10-14 21:50     ` Verma, Vishal L
2021-10-07  8:21 ` [ndctl PATCH v4 11/17] libcxl: add a stub interface to determine whether a memdev is active Vishal Verma
2021-10-14 19:59   ` Dan Williams [this message]
2021-10-07  8:21 ` [ndctl PATCH v4 12/17] libcxl: add interfaces for label operations Vishal Verma
2021-10-14 21:27   ` Dan Williams
2021-10-14 22:18     ` Verma, Vishal L
2021-10-14 22:24     ` Verma, Vishal L
2021-10-14 22:45       ` Dan Williams
2021-10-07  8:21 ` [ndctl PATCH v4 13/17] cxl: add commands to read, write, and zero labels Vishal Verma
2021-10-14 22:34   ` Dan Williams
2021-10-07  8:21 ` [ndctl PATCH v4 14/17] Documentation/cxl: add library API documentation Vishal Verma
2021-10-14 23:31   ` Dan Williams
2021-11-05 18:58   ` Dan Williams
2021-10-07  8:21 ` [ndctl PATCH v4 15/17] ndctl: Add CXL packages to the RPM spec Vishal Verma
2021-10-14 23:33   ` Dan Williams
2021-10-07  8:21 ` [ndctl PATCH v4 16/17] cxl-cli: add bash completion Vishal Verma
2021-10-14 23:34   ` Dan Williams
2021-10-07  8:21 ` [ndctl PATCH v4 17/17] cxl: add health information to cxl-list Vishal Verma
2021-10-11 22:07   ` Verma, Vishal L
2021-10-15  0:09     ` Dan Williams
2021-10-14 23:42   ` Verma, Vishal L
2021-10-15 21:15     ` Dan Williams

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