linux-kernel - Re: [PATCH 4/7] drivers/perf: hisi_pcie: Check the target filter properly

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Date: Wed, 21 Feb 2024 17:46:07 +0800
From: Yicong Yang <yangyicong@...wei.com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
CC: <yangyicong@...ilicon.com>, <will@...nel.org>, <mark.rutland@....com>,
	<hejunhao3@...wei.com>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <linuxarm@...wei.com>,
	<prime.zeng@...ilicon.com>, <fanghao11@...wei.com>
Subject: Re: [PATCH 4/7] drivers/perf: hisi_pcie: Check the target filter
 properly

On 2024/2/8 20:29, Jonathan Cameron wrote:
> On Sun, 4 Feb 2024 15:45:24 +0800
> Yicong Yang <yangyicong@...wei.com> wrote:
> 
>> From: Junhao He <hejunhao3@...wei.com>
>>
>> The PMU can monitor traffic of certain target Root Port or downstream
>> target Endpoint. User can specify the target filter by the "port" or
>> "bdf" option respectively. The PMU can only monitor the Root Port or
>> Endpoint on the same PCIe core so the value of "port" or "bdf" should
>> be valid and will be checked by the driver.
>>
>> Currently at least and only one of "port" and "bdf" option must be set.
>> If "port" filter is not set or is set explicitly to zero (default),
>> driver will regard the user specifies a "bdf" option since "port" option
>> is a bitmask of the target Root Ports and zero is not a valid
>> value.
>>
>> If user not explicitly set "port" or "bdf" filter, the driver uses "bdf"
>> default value (zero) to set target filter, but driver will skip the
>> check of bdf=0, although it's a valid value (meaning 0000:000:00.0).
>> Then the user just gets zero.
>>
>> Therefore, we need to check if both "port" and "bdf" are invalid, then
>> return failure and report warning.
>>
>> Testing:
>> before the patch:
>>                    0      hisi_pcie0_core1/rx_mrd_flux/
>>                    0      hisi_pcie0_core1/rx_mrd_flux,port=0/
>>               24,124      hisi_pcie0_core1/rx_mrd_flux,port=1/
>>                    0      hisi_pcie0_core1/rx_mrd_flux,bdf=0/
>>      <not supported>      hisi_pcie0_core1/rx_mrd_flux,bdf=1/
> 
> Nice to include an example that works for bdf
> 			    hisi_pcie0_core1/rx_mrd_flux,bdf=1,port=0 
> or something like that?
>>
>> after the patch:
>>      <not supported>      hisi_pcie0_core1/rx_mrd_flux/
>>      <not supported>      hisi_pcie0_core1/rx_mrd_flux,port=0/
>>               24,153      hisi_pcie0_core1/rx_mrd_flux,port=1/
>>      <not supported>      hisi_pcie0_core1/rx_mrd_flux,bdf=0/
>>      <not supported>      hisi_pcie0_core1/rx_mrd_flux,bdf=1/
>>
>> Signed-off-by: Junhao He <hejunhao3@...wei.com>
>> Signed-off-by: Yicong Yang <yangyicong@...ilicon.com>
> 
> Clearly the current situation is wrong, but perhaps we can
> have a more intuitive scheme (could be added as a follow up patch)
> and have the driver figure out which port the bdf lies below?
> 
> Maybe that's a job for userspace tooling rather than the driver, but
> the driver already has verification code and it wouldn't be hard
> to not just check the rp is ours, but also set the filter to specify
> that rp, or maybe just set the mask to include them all?
> 

To do a check should be simple, we can decode the bdf and find the target
endpoint and related root port for doing the check.

Another example is what we've done in hisi_ptt that we maintian a list of
supported root ports and endpoints, but that will be a bit more complex.

> Jonathan
> 
> 
>> ---
>>  drivers/perf/hisilicon/hisi_pcie_pmu.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/perf/hisilicon/hisi_pcie_pmu.c b/drivers/perf/hisilicon/hisi_pcie_pmu.c
>> index 83be3390686c..b91f03c02c57 100644
>> --- a/drivers/perf/hisilicon/hisi_pcie_pmu.c
>> +++ b/drivers/perf/hisilicon/hisi_pcie_pmu.c
>> @@ -306,10 +306,10 @@ static bool hisi_pcie_pmu_valid_filter(struct perf_event *event,
>>  	if (hisi_pcie_get_trig_len(event) > HISI_PCIE_TRIG_MAX_VAL)
>>  		return false;
>>  
>> -	if (requester_id) {
>> -		if (!hisi_pcie_pmu_valid_requester_id(pcie_pmu, requester_id))
>> -			return false;
>> -	}
>> +	/* Need to explicitly set filter of "port" or "bdf" */
>> +	if (!hisi_pcie_get_port(event) &&
>> +	    !hisi_pcie_pmu_valid_requester_id(pcie_pmu, requester_id))
>> +		return false;
>>  
>>  	return true;
>>  }
> 
> .
>