linux-kernel - Re: [PATCH v3 18/27] powerpc/powernv/pmem: Add controller dump IOCTLs

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Date:   Fri, 06 Mar 2020 14:34:23 +1100
From:   "Alastair D'Silva" <alastair@....ibm.com>
To:     Andrew Donnellan <ajd@...ux.ibm.com>
Cc:     "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        "Oliver O'Halloran" <oohall@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Frederic Barrat <fbarrat@...ux.ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh@...nel.org>,
        Anton Blanchard <anton@...abs.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>,
        Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>,
        Cédric Le Goater <clg@...d.org>,
        Anju T Sudhakar <anju@...ux.vnet.ibm.com>,
        Hari Bathini <hbathini@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kurz <groug@...d.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-nvdimm@...ts.01.org, linux-mm@...ck.org
Subject: Re: [PATCH v3 18/27] powerpc/powernv/pmem: Add controller dump
 IOCTLs

On Wed, 2020-03-04 at 17:53 +1100, Andrew Donnellan wrote:
> On 21/2/20 2:27 pm, Alastair D'Silva wrote:
> > +static int ioctl_controller_dump_data(struct ocxlpmem *ocxlpmem,
> > +		struct ioctl_ocxl_pmem_controller_dump_data __user
> > *uarg)
> > +{
> > +	struct ioctl_ocxl_pmem_controller_dump_data args;
> > +	u16 i;
> > +	u64 val;
> > +	int rc;
> > +
> > +	if (copy_from_user(&args, uarg, sizeof(args)))
> > +		return -EFAULT;
> > +
> > +	if (args.buf_size % 8)
> > +		return -EINVAL;
> > +
> > +	if (args.buf_size > ocxlpmem->admin_command.data_size)
> > +		return -EINVAL;
> > +
> > +	mutex_lock(&ocxlpmem->admin_command.lock);
> > +
> > +	rc = admin_command_request(ocxlpmem,
> > ADMIN_COMMAND_CONTROLLER_DUMP);
> > +	if (rc)
> > +		goto out;
> > +
> > +	val = ((u64)args.offset) << 32;
> > +	val |= args.buf_size;
> > +	rc = ocxl_global_mmio_write64(ocxlpmem->ocxl_afu,
> > +				      ocxlpmem-
> > >admin_command.request_offset + 0x08,
> > +				      OCXL_LITTLE_ENDIAN, val);
> > +	if (rc)
> > +		goto out;
> > +
> > +	rc = admin_command_execute(ocxlpmem);
> > +	if (rc)
> > +		goto out;
> > +
> > +	rc = admin_command_complete_timeout(ocxlpmem,
> > +					    ADMIN_COMMAND_CONTROLLER_DU
> > MP);
> > +	if (rc < 0) {
> > +		dev_warn(&ocxlpmem->dev, "Controller dump timed
> > out\n");
> > +		goto out;
> > +	}
> > +
> > +	rc = admin_response(ocxlpmem);
> > +	if (rc < 0)
> > +		goto out;
> > +	if (rc != STATUS_SUCCESS) {
> > +		warn_status(ocxlpmem,
> > +			    "Unexpected status from retrieve error
> > log",
> 
> Controller dump
> 

Ok

> > +			    rc);
> > +		goto out;
> > +	}
> > +
> > +	for (i = 0; i < args.buf_size; i += 8) {
> > +		u64 val;
> > +
> > +		rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> > +					     ocxlpmem-
> > >admin_command.data_offset + i,
> > +					     OCXL_HOST_ENDIAN, &val);
> 
> Is a controller dump something where we want to do endian swapping?
> 

No, we just have raw binary data that we want to pass through.
OCXL_HOST_ENDIAN does no swapping.

> Any reason we're not doing the usual check of the data identifier, 
> additional data length etc?
> 

I'll add that

> > +		if (rc)
> > +			goto out;
> > +
> > +		if (copy_to_user(&args.buf[i], &val, sizeof(u64))) {
> > +			rc = -EFAULT;
> > +			goto out;
> > +		}
> > +	}
> > +
> > +	if (copy_to_user(uarg, &args, sizeof(args))) {
> > +		rc = -EFAULT;
> > +		goto out;
> > +	}
> > +
> > +	rc = admin_response_handled(ocxlpmem);
> > +	if (rc)
> > +		goto out;
> > +
> > +out:
> > +	mutex_unlock(&ocxlpmem->admin_command.lock);
> > +	return rc;
> > +}
> > +
> > +int request_controller_dump(struct ocxlpmem *ocxlpmem)
> > +{
> > +	int rc;
> > +	u64 busy = 1;
> > +
> > +	rc = ocxl_global_mmio_set64(ocxlpmem->ocxl_afu,
> > GLOBAL_MMIO_CHIC,
> > +				    OCXL_LITTLE_ENDIAN,
> > +				    GLOBAL_MMIO_CHI_CDA);
> 
> This return code is ignored
> 
> > +
> > +
> > +	rc = ocxl_global_mmio_set64(ocxlpmem->ocxl_afu,
> > GLOBAL_MMIO_HCI,
> > +				    OCXL_LITTLE_ENDIAN,
> > +				    GLOBAL_MMIO_HCI_CONTROLLER_DUMP);
> > +	if (rc)
> > +		return rc;
> > +
> > +	while (busy) {
> > +		rc = ocxl_global_mmio_read64(ocxlpmem->ocxl_afu,
> > +					     GLOBAL_MMIO_HCI,
> > +					     OCXL_LITTLE_ENDIAN,
> > &busy);
> > +		if (rc)
> > +			return rc;
> > +
> > +		busy &= GLOBAL_MMIO_HCI_CONTROLLER_DUMP;
> > +		cond_resched();
> > +	}
> > +
> > +	return 0;
> > +}
> 
> 
-- 
Alastair D'Silva
Open Source Developer
Linux Technology Centre, IBM Australia
mob: 0423 762 819