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Subject: Re: [PATCH v3 19/27] powerpc/powernv/pmem: Add an IOCTL to report
 controller statistics
From:   "Alastair D'Silva" <alastair@au1.ibm.com>
To:     Andrew Donnellan <ajd@linux.ibm.com>
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>,
        =?ISO-8859-1?Q?C=E9dric?= 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
Date:   Thu, 12 Mar 2020 15:47:14 +1100
In-Reply-To: <c0002b11-7f54-38d3-4ae2-9008a5cc0b61@linux.ibm.com>
References: <20200221032720.33893-1-alastair@au1.ibm.com>
         <20200221032720.33893-20-alastair@au1.ibm.com>
         <c0002b11-7f54-38d3-4ae2-9008a5cc0b61@linux.ibm.com>
Organization: IBM Australia
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On Thu, 2020-03-05 at 11:46 +1100, Andrew Donnellan wrote:
> 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_COL
> > LECTED);
> >   }
> >   
> > +/**
> > + * 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
> 

I don't think I've seen a comment yet on these particular blocks. Can
you suggest a better return value?

> > +	}
> > +
> > +	*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_ST
> > ATS);
> > +	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)

Ok

> 
> > +
> > +	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?
> 

It looks like my implementation is out of date. I'll bring it in line
with the spec.

> > +
> > +	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
> 
Ditto

> > +	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
> 
Ditto

> > +	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
> 

Ok

> > +
> > +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(OCX
> > L_PMEM_MAGIC, 0x02)
> >   #define IOCTL_OCXL_PMEM_CONTROLLER_DUMP_DATA		_IOWR(O
> > CXL_PMEM_MAGIC, 0x03, struct ioctl_ocxl_pmem_controller_dump_data)
> >   #define IOCTL_OCXL_PMEM_CONTROLLER_DUMP_COMPLETE	_IO(OCXL_PMEM_M
> > AGIC, 0x04)
> > +#define IOCTL_OCXL_PMEM_CONTROLLER_STATS		_IO(OCXL_PMEM_M
> > AGIC, 0x05)
> >   
> >   #endif /* _UAPI_OCXL_SCM_H */
> > 
-- 
Alastair D'Silva
Open Source Developer
Linux Technology Centre, IBM Australia
mob: 0423 762 819