Subject: Re: [PATCH] powerpc/nvdimm: Add support for multibyte read/write for metadata

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Thu, 06 Jun 2019 18:19:52 +0530

Alexey Kardashevskiy <[email-masked]> writes:

> On 02/06/2019 14:43, Aneesh Kumar K.V wrote:
>> SCM_READ/WRITE_MEATADATA hcall supports multibyte read/write. This patch
>> updates the metadata read/write to use 1, 2, 4 or 8 byte read/write as
>> mentioned in PAPR document.
>> 
>> READ/WRITE_METADATA hcall supports the 1, 2, 4, or 8 bytes read/write.
>> For other values hcall results H_P3.
>> 
>> Hypervisor stores the metadata contents in big-endian format and in-order
>> to enable read/write in different granularity, we need to switch the contents
>> to big-endian before calling HCALL.
>> 
>> Based on an patch from Oliver O'Halloran <[email-masked]>
>> Signed-off-by: Aneesh Kumar K.V <[email-masked]>
>> ---
>>  arch/powerpc/platforms/pseries/papr_scm.c | 104 +++++++++++++++++-----
>>  1 file changed, 82 insertions(+), 22 deletions(-)
>> 
>> diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
>> index 0176ce66673f..e33cebb8ee6c 100644
>> --- a/arch/powerpc/platforms/pseries/papr_scm.c
>> +++ b/arch/powerpc/platforms/pseries/papr_scm.c
>> @@ -97,42 +97,102 @@ static int drc_pmem_unbind(struct papr_scm_priv *p)
>>  }
>>  
>>  static int papr_scm_meta_get(struct papr_scm_priv *p,
>> -			struct nd_cmd_get_config_data_hdr *hdr)
>> +			     struct nd_cmd_get_config_data_hdr *hdr)
>>  {
>>  	unsigned long data[PLPAR_HCALL_BUFSIZE];
>> +	unsigned long offset, data_offset;
>> +	int len, read;
>>  	int64_t ret;
>>  
>> -	if (hdr->in_offset >= p->metadata_size || hdr->in_length != 1)
>> +	if ((hdr->in_offset + hdr->in_length) >= p->metadata_size)
>>  		return -EINVAL;
>>  
>> -	ret = plpar_hcall(H_SCM_READ_METADATA, data, p->drc_index,
>> -			hdr->in_offset, 1);
>> -
>> -	if (ret == H_PARAMETER) /* bad DRC index */
>> -		return -ENODEV;
>> -	if (ret)
>> -		return -EINVAL; /* other invalid parameter */
>> -
>> -	hdr->out_buf[0] = data[0] & 0xff;
>> -
>> +	for (len = hdr->in_length; len; len -= read) {
>> +
>> +		data_offset = hdr->in_length - len;
>> +		offset = hdr->in_offset + data_offset;
>> +
>> +		if (len >= 8)
>> +			read = 8;
>> +		else if (len >= 4)
>> +			read = 4;
>> +		else if ( len >= 2)
>
> Do not need a space before "len".

Will fix in next update

>
>
>> +			read = 2;
>> +		else
>> +			read = 1;
>> +
>> +		ret = plpar_hcall(H_SCM_READ_METADATA, data, p->drc_index,
>> +				  offset, read);
>> +
>> +		if (ret == H_PARAMETER) /* bad DRC index */
>> +			return -ENODEV;
>> +		if (ret)
>> +			return -EINVAL; /* other invalid parameter */
>> +
>> +		switch (read) {
>> +		case 8:
>> +			*(uint64_t *)(hdr->out_buf + data_offset) = be64_to_cpu(data[0]);
>> +			break;
>> +		case 4:
>> +			*(uint32_t *)(hdr->out_buf + data_offset) = be32_to_cpu(data[0] & 0xffffffff);
>> +			break;
>> +
>> +		case 2:
>> +			*(uint16_t *)(hdr->out_buf + data_offset) = be16_to_cpu(data[0] & 0xffff);
>> +			break;
>> +
>> +		case 1:
>> +			*(uint32_t *)(hdr->out_buf + data_offset) = (data[0] & 0xff);
>
>
> Memory corruption, should be uint8_t*.

Good catch. That also resulted in an error on big endian kernel. Will
fix that in next update
>
>
>> +			break;
>> +		}
>> +	}
>>  	return 0;
>>  }
>>  
>>  static int papr_scm_meta_set(struct papr_scm_priv *p,
>> -			struct nd_cmd_set_config_hdr *hdr)
>> +			     struct nd_cmd_set_config_hdr *hdr)
>>  {
>> +	unsigned long offset, data_offset;
>> +	int len, wrote;
>> +	unsigned long data;
>> +	__be64 data_be;
>>  	int64_t ret;
>>  
>> -	if (hdr->in_offset >= p->metadata_size || hdr->in_length != 1)
>> +	if ((hdr->in_offset + hdr->in_length) >= p->metadata_size)
>>  		return -EINVAL;
>>  
>> -	ret = plpar_hcall_norets(H_SCM_WRITE_METADATA,
>> -			p->drc_index, hdr->in_offset, hdr->in_buf[0], 1);
>> -
>> -	if (ret == H_PARAMETER) /* bad DRC index */
>> -		return -ENODEV;
>> -	if (ret)
>> -		return -EINVAL; /* other invalid parameter */
>> +	for (len = hdr->in_length; len; len -= wrote) {
>> +
>> +		data_offset = hdr->in_length - len;
>> +		offset = hdr->in_offset + data_offset;
>> +
>> +		if (len >= 8) {
>> +			data = *(uint64_t *)(hdr->in_buf + data_offset);
>> +			data_be = cpu_to_be64(data);
>> +			wrote = 8;
>> +		} else if (len >= 4) {
>> +			data = *(uint32_t *)(hdr->in_buf + data_offset);
>> +			data &= 0xffffffff;
>
>
> Why do you need &0xffffffff here and below (&0xffff, &0xff)? uint32_t is
> unsigned type so the sign bit won't be extended.

Sure. I just want to make sure we don't take extra data. For now I will
keep it as it is and let Michael Ellerman decide to drop that?

>
>
>> +			data_be = cpu_to_be32(data);
>> +			wrote = 4;
>> +		} else if (len >= 2) {
>> +			data = *(uint16_t *)(hdr->in_buf + data_offset);
>> +			data &= 0xffff;
>> +			data_be = cpu_to_be16(data);
>> +			wrote = 2;
>> +		} else {
>> +			data_be = *(uint8_t *)(hdr->in_buf + data_offset);
>> +			data_be &= 0xff;
>> +			wrote = 1;
>> +		}
>> +
>> +		ret = plpar_hcall_norets(H_SCM_WRITE_METADATA, p->drc_index,
>> +					 offset, data_be, wrote);
>> +		if (ret == H_PARAMETER) /* bad DRC index */
>> +			return -ENODEV;
>> +		if (ret)
>> +			return -EINVAL; /* other invalid parameter */
>> +	}
>>  
>>  	return 0;
>>  }
>> @@ -154,7 +214,7 @@ int papr_scm_ndctl(struct nvdimm_bus_descriptor *nd_desc, struct nvdimm *nvdimm,
>>  		get_size_hdr = buf;
>>  
>>  		get_size_hdr->status = 0;
>> -		get_size_hdr->max_xfer = 1;
>> +		get_size_hdr->max_xfer = 8;
>>  		get_size_hdr->config_size = p->metadata_size;
>>  		*cmd_rc = 0;
>>  		break;
>> 
>
> -- 
> Alexey

Thanks for the review
-aneesh