linux-kernel - Re: [PATCH v5 3/6] fpga: m10bmc-sec: expose max10 flash update count

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Date:   Sun, 15 Nov 2020 12:03:30 -0800
From:   Moritz Fischer <mdf@...nel.org>
To:     Russ Weight <russell.h.weight@...el.com>
Cc:     mdf@...nel.org, lee.jones@...aro.org, linux-fpga@...r.kernel.org,
        linux-kernel@...r.kernel.org, trix@...hat.com, lgoncalv@...hat.com,
        yilun.xu@...el.com, hao.wu@...el.com, matthew.gerlach@...el.com
Subject: Re: [PATCH v5 3/6] fpga: m10bmc-sec: expose max10 flash update count

On Fri, Nov 13, 2020 at 04:55:56PM -0800, Russ Weight wrote:
> Extend the MAX10 BMC Secure Update driver to provide a
> sysfs file to expose the flash update count for the FPGA
> user image.
> 
> Signed-off-by: Russ Weight <russell.h.weight@...el.com>
> Reviewed-by: Tom Rix <trix@...hat.com>
> ---
> v5:
>   - Renamed sysfs node user_flash_count to flash_count and updated the
>     sysfs documentation accordingly.
> v4:
>   - Moved the sysfs file for displaying the flash count from the
>     FPGA Security Manager class driver to here. The
>     m10bmc_user_flash_count() function is removed and the
>     functionality is moved into a user_flash_count_show()
>     function.
>   - Added ABI documentation for the new sysfs entry
> v3:
>   - Changed: iops -> sops, imgr -> smgr, IFPGA_ -> FPGA_, ifpga_ to fpga_
>   - Changed "MAX10 BMC Secure Engine driver" to "MAX10 BMC Secure Update
>     driver"
>   - Removed wrapper functions (m10bmc_raw_*, m10bmc_sys_*). The
>     underlying functions are now called directly.
> v2:
>   - Renamed get_qspi_flash_count() to m10bmc_user_flash_count()
>   - Minor code cleanup per review comments
>   - Added m10bmc_ prefix to functions in m10bmc_iops structure
> ---
>  .../testing/sysfs-driver-intel-m10-bmc-secure |  8 +++++
>  drivers/fpga/intel-m10-bmc-secure.c           | 34 +++++++++++++++++++
>  2 files changed, 42 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-driver-intel-m10-bmc-secure b/Documentation/ABI/testing/sysfs-driver-intel-m10-bmc-secure
> index 2992488b717a..73a3aba750e8 100644
> --- a/Documentation/ABI/testing/sysfs-driver-intel-m10-bmc-secure
> +++ b/Documentation/ABI/testing/sysfs-driver-intel-m10-bmc-secure
> @@ -27,3 +27,11 @@ Description:	Read only. Returns the root entry hash for the BMC image
>  		"hash not programmed".  This file is only visible if the
>  		underlying device supports it.
>  		Format: "0x%x".
> +
> +What:		/sys/bus/platform/devices/n3000bmc-secure.*.auto/security/flash_count
> +Date:		Oct 2020
> +KernelVersion:  5.11
> +Contact:	Russ Weight <russell.h.weight@...el.com>
> +Description:	Read only. Returns number of times the secure update
> +		staging area has been flashed.
> +		Format: "%u".
> diff --git a/drivers/fpga/intel-m10-bmc-secure.c b/drivers/fpga/intel-m10-bmc-secure.c
> index 198bc8273d6b..6ad897001086 100644
> --- a/drivers/fpga/intel-m10-bmc-secure.c
> +++ b/drivers/fpga/intel-m10-bmc-secure.c
> @@ -11,6 +11,7 @@
>  #include <linux/mfd/intel-m10-bmc.h>
>  #include <linux/module.h>
>  #include <linux/platform_device.h>
> +#include <linux/slab.h>
>  
>  struct m10bmc_sec {
>  	struct device *dev;
> @@ -77,7 +78,40 @@ DEVICE_ATTR_SEC_REH_RO(bmc, BMC_PROG_MAGIC, BMC_PROG_ADDR, BMC_REH_ADDR);
>  DEVICE_ATTR_SEC_REH_RO(sr, SR_PROG_MAGIC, SR_PROG_ADDR, SR_REH_ADDR);
>  DEVICE_ATTR_SEC_REH_RO(pr, PR_PROG_MAGIC, PR_PROG_ADDR, PR_REH_ADDR);
>  
> +#define FLASH_COUNT_SIZE 4096	/* count stored as inverted bit vector */
> +
> +static ssize_t flash_count_show(struct device *dev,
> +				struct device_attribute *attr, char *buf)
> +{
> +	struct m10bmc_sec *sec = dev_get_drvdata(dev);
> +	unsigned int stride = regmap_get_reg_stride(sec->m10bmc->regmap);
> +	unsigned int num_bits = FLASH_COUNT_SIZE * 8;
> +	u8 *flash_buf;
> +	int cnt, ret;

(Nit) Can you make this:

	struct m10bmc_sec *sec = dev_get_drvdata(dev);
	unsigned int stride, num_bits;
	u8 *flash_buf;
	int cnt, ret;

	stride = regmap_get_reg_stride(sec->m10bmc->regmap);
	num_bits = FLASH_COUNT_SIZE * 8;


> +
> +	flash_buf = kmalloc(FLASH_COUNT_SIZE, GFP_KERNEL);
> +	if (!flash_buf)
> +		return -ENOMEM;
> +
> +	ret = regmap_bulk_read(sec->m10bmc->regmap, STAGING_FLASH_COUNT,
> +			       flash_buf, FLASH_COUNT_SIZE / stride);
> +	if (ret) {
> +		dev_err(sec->dev,
> +			"failed to read flash count: %x cnt %x: %d\n",
> +			STAGING_FLASH_COUNT, FLASH_COUNT_SIZE / stride, ret);
> +		goto exit_free;
> +	}
> +	cnt = num_bits - bitmap_weight((unsigned long *)flash_buf, num_bits);
> +
> +exit_free:
> +	kfree(flash_buf);
> +
> +	return ret ? : sysfs_emit(buf, "%u\n", cnt);
> +}
> +static DEVICE_ATTR_RO(flash_count);
> +
>  static struct attribute *m10bmc_security_attrs[] = {
> +	&dev_attr_flash_count.attr,
>  	&dev_attr_bmc_root_entry_hash.attr,
>  	&dev_attr_sr_root_entry_hash.attr,
>  	&dev_attr_pr_root_entry_hash.attr,
> -- 
> 2.25.1
> 

Otherwise looks good to me,

- Moritz