Subject: Re: [PATCH v2 07/11] powerpc: add a shared interface to get gpci version and capabilities

From: Cody P Schafer <[email-masked]>
Date: Tue, 25 Feb 2014 13:20:59 -0800

On 02/24/2014 07:33 PM, Michael Ellerman wrote:
> [PATCH v2 07/11] powerpc: add a shared interface to get gpci version and capabilities
>
> All the patches that touch perf should be "powerpc/perf: foo"

Ok.

> On Fri, 2014-14-02 at 22:02:11 UTC, Cody P Schafer wrote:
>> ...
>
> I realise this is a fairly small patch but a changelog is still nice. You could
> for example mention that we don't currently use .ga, .expanded or .lab but
> we're adding the logic anyway because ...
>

Well, we do use them to expose some more information to the user (via 
sysfs attributes). Always nice to know what capabilities are enabled.

But sure, I can explain why each bit in that structure is a good idea.

>
>> Signed-off-by: Cody P Schafer <[email-masked]>
>> ---
>>   arch/powerpc/perf/hv-common.c | 39 +++++++++++++++++++++++++++++++++++++++
>>   arch/powerpc/perf/hv-common.h | 17 +++++++++++++++++
>>   2 files changed, 56 insertions(+)
>>   create mode 100644 arch/powerpc/perf/hv-common.c
>>   create mode 100644 arch/powerpc/perf/hv-common.h
>>
>> diff --git a/arch/powerpc/perf/hv-common.c b/arch/powerpc/perf/hv-common.c
>> new file mode 100644
>> index 0000000..47e02b3
>> --- /dev/null
>> +++ b/arch/powerpc/perf/hv-common.c
>> @@ -0,0 +1,39 @@
>> +#include <asm/io.h>
>> +#include <asm/hvcall.h>
>> +
>> +#include "hv-gpci.h"
>> +#include "hv-common.h"
>> +
>> +unsigned long hv_perf_caps_get(struct hv_perf_caps *caps)
>> +{
>> +	unsigned long r;
>> +	struct p {
>> +		struct hv_get_perf_counter_info_params params;
>> +		struct cv_system_performance_capabilities caps;
>> +	} __packed __aligned(sizeof(uint64_t));
>> +
>> +	struct p arg = {
>> +		.params = {
>> +			.counter_request = cpu_to_be32(
>> +					CIR_SYSTEM_PERFORMANCE_CAPABILITIES),
>> +			.starting_index = cpu_to_be32(-1),
>> +			.counter_info_version_in = 0,
>> +		}
>> +	};
>> +
>> +	r = plpar_hcall_norets(H_GET_PERF_COUNTER_INFO,
>> +			       virt_to_phys(&arg), sizeof(arg));
>> +
>> +	if (r)
>> +		return r;
>> +
>> +	pr_devel("capability_mask: 0x%x\n", arg.caps.capability_mask);
>> +
>> +	caps->version = arg.params.counter_info_version_out;
>> +	caps->collect_privileged = !!arg.caps.perf_collect_privileged;
>> +	caps->ga = !!(arg.caps.capability_mask & CV_CM_GA);
>> +	caps->expanded = !!(arg.caps.capability_mask & CV_CM_EXPANDED);
>> +	caps->lab = !!(arg.caps.capability_mask & CV_CM_LAB);
>> +
>> +	return r;
>> +}
>> diff --git a/arch/powerpc/perf/hv-common.h b/arch/powerpc/perf/hv-common.h
>> new file mode 100644
>> index 0000000..7e615bd
>> --- /dev/null
>> +++ b/arch/powerpc/perf/hv-common.h
>> @@ -0,0 +1,17 @@
>> +#ifndef LINUX_POWERPC_PERF_HV_COMMON_H_
>> +#define LINUX_POWERPC_PERF_HV_COMMON_H_
>> +
>> +#include <linux/types.h>
>> +
>> +struct hv_perf_caps {
>> +	u16 version;
>> +	u16 collect_privileged:1,
>> +	    ga:1,
>> +	    expanded:1,
>> +	    lab:1,
>> +	    unused:12;
>> +};
>> +
>> +unsigned long hv_perf_caps_get(struct hv_perf_caps *caps);
>> +
>> +#endif
>> --
>> 1.8.5.4
>>
>>
>