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Subject: Re: [PATCH v3 19/27] powerpc/powernv/pmem: Add an IOCTL to report
 controller statistics
To:     "Alastair D'Silva" <alastair@au1.ibm.com>, alastair@d-silva.org
Cc:     "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
        "Oliver O'Halloran" <oohall@gmail.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Frederic Barrat <fbarrat@linux.ibm.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Ira Weiny <ira.weiny@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Rob Herring <robh@kernel.org>,
        Anton Blanchard <anton@ozlabs.org>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>,
        Madhavan Srinivasan <maddy@linux.vnet.ibm.com>,
        =?UTF-8?Q?C=c3=a9dric_Le_Goater?= <clg@kaod.org>,
        Anju T Sudhakar <anju@linux.vnet.ibm.com>,
        Hari Bathini <hbathini@linux.ibm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Greg Kurz <groug@kaod.org>,
        Nicholas Piggin <npiggin@gmail.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Alexey Kardashevskiy <aik@ozlabs.ru>,
        linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        linux-nvdimm@lists.01.org, linux-mm@kvack.org
References: <20200221032720.33893-1-alastair@au1.ibm.com>
 <20200221032720.33893-20-alastair@au1.ibm.com>
From:   Andrew Donnellan <ajd@linux.ibm.com>
Date:   Thu, 5 Mar 2020 11:46:27 +1100
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On 21/2/20 2:27 pm, Alastair D'Silva wrote:
> From: Alastair D'Silva <alastair@d-silva.org>
> 
> The controller can report a number of statistics that are useful
> in evaluating the performance and reliability of the card.
> 
> This patch exposes this information via an IOCTL.
> 
> Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
> ---
>   arch/powerpc/platforms/powernv/pmem/ocxl.c | 185 +++++++++++++++++++++
>   include/uapi/nvdimm/ocxl-pmem.h            |  17 ++
>   2 files changed, 202 insertions(+)
> 
> diff --git a/arch/powerpc/platforms/powernv/pmem/ocxl.c b/arch/powerpc/platforms/powernv/pmem/ocxl.c
> index 2cabafe1fc58..009d4fd29e7d 100644
> --- a/arch/powerpc/platforms/powernv/pmem/ocxl.c
> +++ b/arch/powerpc/platforms/powernv/pmem/ocxl.c
> @@ -758,6 +758,186 @@ static int ioctl_controller_dump_complete(struct ocxlpmem *ocxlpmem)
>   				    GLOBAL_MMIO_HCI_CONTROLLER_DUMP_COLLECTED);
>   }
>   
> +/**
> + * controller_stats_header_parse() - Parse the first 64 bits of the controller stats admin command response
> + * @ocxlpmem: the device metadata
> + * @length: out, returns the number of bytes in the response (excluding the 64 bit header)
> + */
> +static int controller_stats_header_parse(struct ocxlpmem *ocxlpmem,
> +	u32 *length)
> +{
> +	int rc;
> +	u64 val;
> +
> +	u16 data_identifier;
> +	u32 data_length;
> +
> +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> +				     ocxlpmem->admin_command.data_offset,
> +				     OCXL_LITTLE_ENDIAN, &val);
> +	if (rc)
> +		return rc;
> +
> +	data_identifier = val >> 48;
> +	data_length = val & 0xFFFFFFFF;
> +
> +	if (data_identifier != 0x4353) { // 'CS'
> +		dev_err(&ocxlpmem->dev,
> +			"Bad data identifier for controller stats, expected 'CS', got '%-.*s'\n",
> +			2, (char *)&data_identifier);
> +		return -EINVAL;

Same comment as earlier patches re EINVAL

> +	}
> +
> +	*length = data_length;
> +	return 0;
> +}
> +
> +static int ioctl_controller_stats(struct ocxlpmem *ocxlpmem,
> +				  struct ioctl_ocxl_pmem_controller_stats __user *uarg)
> +{
> +	struct ioctl_ocxl_pmem_controller_stats args;
> +	u32 length;
> +	int rc;
> +	u64 val;
> +
> +	memset(&args, '\0', sizeof(args));
> +
> +	mutex_lock(&ocxlpmem->admin_command.lock);
> +
> +	rc = admin_command_request(ocxlpmem, ADMIN_COMMAND_CONTROLLER_STATS);
> +	if (rc)
> +		goto out;
> +
> +	rc = ocxl_global_mmio_write64(ocxlpmem->ocxl_afu,
> +				      ocxlpmem->admin_command.request_offset + 0x08,
> +				      OCXL_LITTLE_ENDIAN, 0);
> +	if (rc)
> +		goto out;
> +
> +	rc = admin_command_execute(ocxlpmem);
> +	if (rc)
> +		goto out;
> +
> +
> +	rc = admin_command_complete_timeout(ocxlpmem,
> +					    ADMIN_COMMAND_CONTROLLER_STATS);
> +	if (rc < 0) {
> +		dev_warn(&ocxlpmem->dev, "Controller stats timed out\n");
> +		goto out;
> +	}
> +
> +	rc = admin_response(ocxlpmem);
> +	if (rc < 0)
> +		goto out;
> +	if (rc != STATUS_SUCCESS) {
> +		warn_status(ocxlpmem,
> +			    "Unexpected status from controller stats", rc);
> +		goto out;
> +	}
> +
> +	rc = controller_stats_header_parse(ocxlpmem, &length);
> +	if (rc)
> +		goto out;
> +
> +	if (length != 0x140)
> +		warn_status(ocxlpmem,
> +			    "Unexpected length for controller stats data, expected 0x140, got 0x%x",
> +			    length);

Might be worth a comment to explain where 0x140 comes from (it looks 
correct from my reading of the spec)

> +
> +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> +				     ocxlpmem->admin_command.data_offset + 0x08 + 0x08,
> +				     OCXL_LITTLE_ENDIAN, &val);
> +	if (rc)
> +		goto out;
> +
> +	args.reset_count = val >> 32;
> +	args.reset_uptime = val & 0xFFFFFFFF;
> +
> +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> +				     ocxlpmem->admin_command.data_offset + 0x08 + 0x10,
> +				     OCXL_LITTLE_ENDIAN, &val);
> +	if (rc)
> +		goto out;
> +
> +	args.power_on_uptime = val >> 32;

We're not collecting life remaining?

> +
> +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> +				     ocxlpmem->admin_command.data_offset + 0x08 + 0x40 + 0x08,
> +				     OCXL_LITTLE_ENDIAN, &args.host_load_count);

My reading of the spec says HLC is at +0x10

> +	if (rc)
> +		goto out;
> +
> +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> +				     ocxlpmem->admin_command.data_offset + 0x08 + 0x40 + 0x10,
> +				     OCXL_LITTLE_ENDIAN, &args.host_store_count);

HSC at +0x18

> +	if (rc)
> +		goto out;
> +
> +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> +				     ocxlpmem->admin_command.data_offset + 0x08 + 0x40 + 0x18,
> +				     OCXL_LITTLE_ENDIAN, &args.media_read_count);

MRC is at +0x50

And you're missing CRU, HLD, HSD

> +	if (rc)
> +		goto out;
> +
> +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> +				     ocxlpmem->admin_command.data_offset + 0x08 + 0x40 + 0x20,
> +				     OCXL_LITTLE_ENDIAN, &args.media_write_count);

MWC at +0x58

> +	if (rc)
> +		goto out;
> +
> +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> +				     ocxlpmem->admin_command.data_offset + 0x08 + 0x40 + 0x28,
> +				     OCXL_LITTLE_ENDIAN, &args.cache_hit_count);

CRHC at +0x90

> +	if (rc)
> +		goto out;
> +
> +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> +				     ocxlpmem->admin_command.data_offset + 0x08 + 0x40 + 0x30,
> +				     OCXL_LITTLE_ENDIAN, &args.cache_miss_count);

This field doesn't seem to exist at all in my copy of the spec

> +	if (rc)
> +		goto out;
> +
> +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> +				     ocxlpmem->admin_command.data_offset + 0x08 + 0x40 + 0x38,
> +				     OCXL_LITTLE_ENDIAN, &args.media_read_latency);

Nor this one

> +	if (rc)
> +		goto out;
> +
> +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> +				     ocxlpmem->admin_command.data_offset + 0x08 + 0x40 + 0x40,
> +				     OCXL_LITTLE_ENDIAN, &args.media_write_latency);

Nor this one

> +	if (rc)
> +		goto out;
> +
> +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> +				     ocxlpmem->admin_command.data_offset + 0x08 + 0x40 + 0x48,
> +				     OCXL_LITTLE_ENDIAN, &args.cache_read_latency);

Nor this one

> +	if (rc)
> +		goto out;
> +
> +	rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> +				     ocxlpmem->admin_command.data_offset + 0x08 + 0x40 + 0x50,
> +				     OCXL_LITTLE_ENDIAN, &args.cache_write_latency);

Nor this one

> +	if (rc)
> +		goto out;
> +
> +	if (copy_to_user(uarg, &args, sizeof(args))) {
> +		rc = -EFAULT;
> +		goto out;
> +	}
> +
> +	rc = admin_response_handled(ocxlpmem);
> +	if (rc)
> +		goto out;
> +
> +	rc = 0;
> +	goto out;

Per Fred this pattern isn't common in the kernel, but perhaps this is 
just personal taste

> +
> +out:
> +	mutex_unlock(&ocxlpmem->admin_command.lock);
> +	return rc;
> +}
> +
>   static long file_ioctl(struct file *file, unsigned int cmd, unsigned long args)
>   {
>   	struct ocxlpmem *ocxlpmem = file->private_data;
> @@ -781,6 +961,11 @@ static long file_ioctl(struct file *file, unsigned int cmd, unsigned long args)
>   	case IOCTL_OCXL_PMEM_CONTROLLER_DUMP_COMPLETE:
>   		rc = ioctl_controller_dump_complete(ocxlpmem);
>   		break;
> +
> +	case IOCTL_OCXL_PMEM_CONTROLLER_STATS:
> +		rc = ioctl_controller_stats(ocxlpmem,
> +					    (struct ioctl_ocxl_pmem_controller_stats __user *)args);
> +		break;
>   	}
>   
>   	return rc;
> diff --git a/include/uapi/nvdimm/ocxl-pmem.h b/include/uapi/nvdimm/ocxl-pmem.h
> index d4d8512d03f7..add223aa2fdb 100644
> --- a/include/uapi/nvdimm/ocxl-pmem.h
> +++ b/include/uapi/nvdimm/ocxl-pmem.h
> @@ -50,6 +50,22 @@ struct ioctl_ocxl_pmem_controller_dump_data {
>   	__u64 reserved[8];
>   };
>   
> +struct ioctl_ocxl_pmem_controller_stats {
> +	__u32 reset_count;
> +	__u32 reset_uptime; /* seconds */
> +	__u32 power_on_uptime; /* seconds */
> +	__u64 host_load_count;
> +	__u64 host_store_count;
> +	__u64 media_read_count;
> +	__u64 media_write_count;
> +	__u64 cache_hit_count;
> +	__u64 cache_miss_count;
> +	__u64 media_read_latency; /* nanoseconds */
> +	__u64 media_write_latency; /* nanoseconds */
> +	__u64 cache_read_latency; /* nanoseconds */
> +	__u64 cache_write_latency; /* nanoseconds */
> +};
> +
>   /* ioctl numbers */
>   #define OCXL_PMEM_MAGIC 0x5C
>   /* SCM devices */
> @@ -57,5 +73,6 @@ struct ioctl_ocxl_pmem_controller_dump_data {
>   #define IOCTL_OCXL_PMEM_CONTROLLER_DUMP			_IO(OCXL_PMEM_MAGIC, 0x02)
>   #define IOCTL_OCXL_PMEM_CONTROLLER_DUMP_DATA		_IOWR(OCXL_PMEM_MAGIC, 0x03, struct ioctl_ocxl_pmem_controller_dump_data)
>   #define IOCTL_OCXL_PMEM_CONTROLLER_DUMP_COMPLETE	_IO(OCXL_PMEM_MAGIC, 0x04)
> +#define IOCTL_OCXL_PMEM_CONTROLLER_STATS		_IO(OCXL_PMEM_MAGIC, 0x05)
>   
>   #endif /* _UAPI_OCXL_SCM_H */
> 

-- 
Andrew Donnellan              OzLabs, ADL Canberra
ajd@linux.ibm.com             IBM Australia Limited