[PATCH v2] powerpc/pseries: read the lpar name from the firmware

[PATCH v2] powerpc/pseries: read the lpar name from the firmware

[Laurent Dufour]

The LPAR name may be changed after the LPAR has been started in the HMC.
In that case lparstat command is not reporting the updated value because it
reads it from the device tree which is read at boot time.

However this value could be read from RTAS.

Adding this value in the /proc/powerpc/lparcfg output allows to read the
updated value.

Cc: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
---
v2:
 address Nathan's comments.
 change title to partition_name aligning with existing partition_id
---
 arch/powerpc/platforms/pseries/lparcfg.c | 53 ++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/arch/powerpc/platforms/pseries/lparcfg.c b/arch/powerpc/platforms/pseries/lparcfg.c
index f71eac74ea92..0deca7b4cd81 100644
--- a/arch/powerpc/platforms/pseries/lparcfg.c
+++ b/arch/powerpc/platforms/pseries/lparcfg.c
@@ -311,6 +311,58 @@ static void parse_mpp_x_data(struct seq_file *m)
 		seq_printf(m, "coalesce_pool_spurr=%ld\n", mpp_x_data.pool_spurr_cycles);
 }
 
+/*
+ * PAPR defines no maximum for the LPAR name, and defines that the maximum
+ * length of the get-system-parameter's output buffer is 4000 plus 2 bytes for
+ * the length. Limit LPAR's name size to 1024
+ */
+#define SPLPAR_LPAR_NAME_MAXLEN	1026
+#define SPLPAR_LPAR_NAME_TOKEN	55
+static void parse_lpar_name(struct seq_file *m)
+{
+	int rc, len, token;
+	unsigned char *local_buffer;
+
+	token = rtas_token("ibm,get-system-parameter");
+	if (token == RTAS_UNKNOWN_SERVICE)
+		return;
+
+	local_buffer = kmalloc(SPLPAR_LPAR_NAME_MAXLEN, GFP_KERNEL);
+	if (!local_buffer)
+		return;
+
+	do {
+		spin_lock(&rtas_data_buf_lock);
+
+		memset(rtas_data_buf, 0, RTAS_DATA_BUF_SIZE);
+		rc = rtas_call(token, 3, 1, NULL, SPLPAR_LPAR_NAME_TOKEN,
+			       __pa(rtas_data_buf), RTAS_DATA_BUF_SIZE);
+		memcpy(local_buffer, rtas_data_buf, SPLPAR_LPAR_NAME_MAXLEN);
+
+		spin_unlock(&rtas_data_buf_lock);
+	} while (rtas_busy_delay(rc));
+
+	if (rc != 0) {
+		pr_err_once(
+			"%s %s Error calling get-system-parameter (0x%x)\n",
+			__FILE__, __func__, rc);
+	} else {
+		local_buffer[SPLPAR_LPAR_NAME_MAXLEN - 1] = '\0';
+		len = local_buffer[0] * 256 + local_buffer[1];
+
+		/*
+		 * Forces an empty string in the weird case fw reports no data.
+		 */
+		if (!len)
+			local_buffer[2] = '\0';
+
+		seq_printf(m, "partition_name=%s\n", local_buffer + 2);
+	}
+
+	kfree(local_buffer);
+}
+
+
 #define SPLPAR_CHARACTERISTICS_TOKEN 20
 #define SPLPAR_MAXLENGTH 1026*(sizeof(char))
 
@@ -496,6 +548,7 @@ static int pseries_lparcfg_data(struct seq_file *m, void *v)
 
 	if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
 		/* this call handles the ibm,get-system-parameter contents */
+		parse_lpar_name(m);
 		parse_system_parameter_string(m);
 		parse_ppp_data(m);
 		parse_mpp_data(m);
-- 
2.34.1

Re: [PATCH v2] powerpc/pseries: read the lpar name from the firmware

[Michael Ellerman]

Hi Laurent,

Just a few minor comments below ...

Laurent Dufour <ldufour@linux.ibm.com> writes:
> The LPAR name may be changed after the LPAR has been started in the HMC.
> In that case lparstat command is not reporting the updated value because it
> reads it from the device tree which is read at boot time.
>
> However this value could be read from RTAS.
>
> Adding this value in the /proc/powerpc/lparcfg output allows to read the
> updated value.
>
> Cc: Nathan Lynch <nathanl@linux.ibm.com>
> Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
> ---
> v2:
>  address Nathan's comments.
>  change title to partition_name aligning with existing partition_id
> ---
>  arch/powerpc/platforms/pseries/lparcfg.c | 53 ++++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
>
> diff --git a/arch/powerpc/platforms/pseries/lparcfg.c b/arch/powerpc/platforms/pseries/lparcfg.c
> index f71eac74ea92..0deca7b4cd81 100644
> --- a/arch/powerpc/platforms/pseries/lparcfg.c
> +++ b/arch/powerpc/platforms/pseries/lparcfg.c
> @@ -311,6 +311,58 @@ static void parse_mpp_x_data(struct seq_file *m)
>  		seq_printf(m, "coalesce_pool_spurr=%ld\n", mpp_x_data.pool_spurr_cycles);
>  }
>  
> +/*
> + * PAPR defines no maximum for the LPAR name, and defines that the maximum
> + * length of the get-system-parameter's output buffer is 4000 plus 2 bytes for
> + * the length. Limit LPAR's name size to 1024
> + */
> +#define SPLPAR_LPAR_NAME_MAXLEN	1026

Why not just allocate the full 4000? That's not much memory in the
scheme of things, and allocating less risks us needing to update this in
future. I realise that's a ridiculously long LPAR name, but still.

> +#define SPLPAR_LPAR_NAME_TOKEN	55

Can you add a comment saying where that value is defined, PAPR?

> +static void parse_lpar_name(struct seq_file *m)

Nitpick, but we're not really parsing it, we're just reading it from firmware.

> +{
> +	int rc, len, token;
> +	unsigned char *local_buffer;
> +
> +	token = rtas_token("ibm,get-system-parameter");
> +	if (token == RTAS_UNKNOWN_SERVICE)
> +		return;
> +
> +	local_buffer = kmalloc(SPLPAR_LPAR_NAME_MAXLEN, GFP_KERNEL);
> +	if (!local_buffer)
> +		return;
> +
> +	do {
> +		spin_lock(&rtas_data_buf_lock);
> +
> +		memset(rtas_data_buf, 0, RTAS_DATA_BUF_SIZE);
> +		rc = rtas_call(token, 3, 1, NULL, SPLPAR_LPAR_NAME_TOKEN,
> +			       __pa(rtas_data_buf), RTAS_DATA_BUF_SIZE);
> +		memcpy(local_buffer, rtas_data_buf, SPLPAR_LPAR_NAME_MAXLEN);

Would be nice to skip the memcpy() if rc is non-zero.

> +		spin_unlock(&rtas_data_buf_lock);
> +	} while (rtas_busy_delay(rc));
> +
> +	if (rc != 0) {
> +		pr_err_once(
> +			"%s %s Error calling get-system-parameter (0x%x)\n",
> +			__FILE__, __func__, rc);
> +	} else {
> +		local_buffer[SPLPAR_LPAR_NAME_MAXLEN - 1] = '\0';
> +		len = local_buffer[0] * 256 + local_buffer[1];

This is kind of a hand rolled be16_to_cpu().

And we also have the + 2 to skip the length in several places.

I feel like the code would be cleaner if we had a type for the result
buffer, eg something like:

union {
	char raw_buffer[1026];
        struct {
        	__be16 len;
                char data[1024];
        };
};

> +		/*
> +		 * Forces an empty string in the weird case fw reports no data.
> +		 */
> +		if (!len)
> +			local_buffer[2] = '\0';
> +
> +		seq_printf(m, "partition_name=%s\n", local_buffer + 2);

Then above you could use the data field rather than having to add the
"2" in both places.

> +	}
> +
> +	kfree(local_buffer);
> +}
> +
> +
>  #define SPLPAR_CHARACTERISTICS_TOKEN 20
>  #define SPLPAR_MAXLENGTH 1026*(sizeof(char))
>  
> @@ -496,6 +548,7 @@ static int pseries_lparcfg_data(struct seq_file *m, void *v)
>  
>  	if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
>  		/* this call handles the ibm,get-system-parameter contents */
> +		parse_lpar_name(m);
>  		parse_system_parameter_string(m);
>  		parse_ppp_data(m);
>  		parse_mpp_data(m);
> -- 
> 2.34.1


cheers

Re: [PATCH v2] powerpc/pseries: read the lpar name from the firmware

[Laurent Dufour]

On 03/12/2021, 13:28:10, Michael Ellerman wrote:
> Hi Laurent,
> 
> Just a few minor comments below ...

Thanks, Michael, for your _major_ comments.

I'll send a version 3 soon.

Laurent.

> 
> Laurent Dufour <ldufour@linux.ibm.com> writes:
>> The LPAR name may be changed after the LPAR has been started in the HMC.
>> In that case lparstat command is not reporting the updated value because it
>> reads it from the device tree which is read at boot time.
>>
>> However this value could be read from RTAS.
>>
>> Adding this value in the /proc/powerpc/lparcfg output allows to read the
>> updated value.
>>
>> Cc: Nathan Lynch <nathanl@linux.ibm.com>
>> Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
>> ---
>> v2:
>>  address Nathan's comments.
>>  change title to partition_name aligning with existing partition_id
>> ---
>>  arch/powerpc/platforms/pseries/lparcfg.c | 53 ++++++++++++++++++++++++
>>  1 file changed, 53 insertions(+)
>>
>> diff --git a/arch/powerpc/platforms/pseries/lparcfg.c b/arch/powerpc/platforms/pseries/lparcfg.c
>> index f71eac74ea92..0deca7b4cd81 100644
>> --- a/arch/powerpc/platforms/pseries/lparcfg.c
>> +++ b/arch/powerpc/platforms/pseries/lparcfg.c
>> @@ -311,6 +311,58 @@ static void parse_mpp_x_data(struct seq_file *m)
>>  		seq_printf(m, "coalesce_pool_spurr=%ld\n", mpp_x_data.pool_spurr_cycles);
>>  }
>>  
>> +/*
>> + * PAPR defines no maximum for the LPAR name, and defines that the maximum
>> + * length of the get-system-parameter's output buffer is 4000 plus 2 bytes for
>> + * the length. Limit LPAR's name size to 1024
>> + */
>> +#define SPLPAR_LPAR_NAME_MAXLEN	1026
> 
> Why not just allocate the full 4000? That's not much memory in the
> scheme of things, and allocating less risks us needing to update this in
> future. I realise that's a ridiculously long LPAR name, but still.
> 
>> +#define SPLPAR_LPAR_NAME_TOKEN	55
> 
> Can you add a comment saying where that value is defined, PAPR?
> 
>> +static void parse_lpar_name(struct seq_file *m)
> 
> Nitpick, but we're not really parsing it, we're just reading it from firmware.
> 
>> +{
>> +	int rc, len, token;
>> +	unsigned char *local_buffer;
>> +
>> +	token = rtas_token("ibm,get-system-parameter");
>> +	if (token == RTAS_UNKNOWN_SERVICE)
>> +		return;
>> +
>> +	local_buffer = kmalloc(SPLPAR_LPAR_NAME_MAXLEN, GFP_KERNEL);
>> +	if (!local_buffer)
>> +		return;
>> +
>> +	do {
>> +		spin_lock(&rtas_data_buf_lock);
>> +
>> +		memset(rtas_data_buf, 0, RTAS_DATA_BUF_SIZE);
>> +		rc = rtas_call(token, 3, 1, NULL, SPLPAR_LPAR_NAME_TOKEN,
>> +			       __pa(rtas_data_buf), RTAS_DATA_BUF_SIZE);
>> +		memcpy(local_buffer, rtas_data_buf, SPLPAR_LPAR_NAME_MAXLEN);
> 
> Would be nice to skip the memcpy() if rc is non-zero.
> 
>> +		spin_unlock(&rtas_data_buf_lock);
>> +	} while (rtas_busy_delay(rc));
>> +
>> +	if (rc != 0) {
>> +		pr_err_once(
>> +			"%s %s Error calling get-system-parameter (0x%x)\n",
>> +			__FILE__, __func__, rc);
>> +	} else {
>> +		local_buffer[SPLPAR_LPAR_NAME_MAXLEN - 1] = '\0';
>> +		len = local_buffer[0] * 256 + local_buffer[1];
> 
> This is kind of a hand rolled be16_to_cpu().
> 
> And we also have the + 2 to skip the length in several places.
> 
> I feel like the code would be cleaner if we had a type for the result
> buffer, eg something like:
> 
> union {
> 	char raw_buffer[1026];
>         struct {
>         	__be16 len;
>                 char data[1024];
>         };
> };
> 
>> +		/*
>> +		 * Forces an empty string in the weird case fw reports no data.
>> +		 */
>> +		if (!len)
>> +			local_buffer[2] = '\0';
>> +
>> +		seq_printf(m, "partition_name=%s\n", local_buffer + 2);
> 
> Then above you could use the data field rather than having to add the
> "2" in both places.
> 
>> +	}
>> +
>> +	kfree(local_buffer);
>> +}
>> +
>> +
>>  #define SPLPAR_CHARACTERISTICS_TOKEN 20
>>  #define SPLPAR_MAXLENGTH 1026*(sizeof(char))
>>  
>> @@ -496,6 +548,7 @@ static int pseries_lparcfg_data(struct seq_file *m, void *v)
>>  
>>  	if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
>>  		/* this call handles the ibm,get-system-parameter contents */
>> +		parse_lpar_name(m);
>>  		parse_system_parameter_string(m);
>>  		parse_ppp_data(m);
>>  		parse_mpp_data(m);
>> -- 
>> 2.34.1
> 
> 
> cheers
>