linux-kernel - Re: [PATCH 5/5] arm-cci: Fix CCI PMU event validation

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Message-ID: <20150317185247.GE8399@arm.com>
Date:	Tue, 17 Mar 2015 18:52:47 +0000
From:	Will Deacon <will.deacon@....com>
To:	"Suzuki K. Poulose" <suzuki.poulose@....com>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Nicolas Pitre <nico@...aro.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Kukjin Kim <kgene@...nel.org>,
	Abhilash Kesavan <a.kesavan@...sung.com>,
	Arnd Bergmann <arnd@...db.de>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Liviu Dudau <Liviu.Dudau@....com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Olof Johansson <olof@...om.net>,
	Pawel Moll <Pawel.Moll@....com>,
	Punit Agrawal <Punit.Agrawal@....com>,
	Sudeep Holla <Sudeep.Holla@....com>,
	Catalin Marinas <Catalin.Marinas@....com>
Subject: Re: [PATCH 5/5] arm-cci: Fix CCI PMU event validation

On Tue, Mar 10, 2015 at 03:18:55PM +0000, Suzuki K. Poulose wrote:
> From: "Suzuki K. Poulose" <suzuki.poulose@....com>
> 
> We mask the event with the CCI_PMU_EVENT_MASK, before passing
> the config to pmu_validate_hw_event(), which causes extra bits
> to be ignored and qualifies an invalid event code as valid.
> 
> e.g,
>  $ perf stat -a -C 0 -e CCI_400/config=0x1ff,name=cycles/ sleep 1
>    Performance counter stats for 'system wide':
> 
>          506951142      cycles
> 
>        1.013879626 seconds time elapsed
> 
> where, cycles has an event coding of 0xff. This patch also removes
> the unnecessary 'event' mask in pmu_write_register, since the config_base
> is set by the pmu code after the event is validated.
> 
> Changes since V2:
>  - Switch to input unsigned long for pmu_validate_hw_event()
> 
> Signed-off-by: Suzuki K. Poulose <suzuki.poulose@....com>
> ---
>  drivers/bus/arm-cci.c |   10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c
> index 581190d..89c86e9 100644
> --- a/drivers/bus/arm-cci.c
> +++ b/drivers/bus/arm-cci.c
> @@ -179,12 +179,15 @@ enum cci400_perf_events {
>  #define CCI_REV_R1_MASTER_PORT_MIN_EV	0x00
>  #define CCI_REV_R1_MASTER_PORT_MAX_EV	0x11
>  
> -static int pmu_validate_hw_event(u8 hw_event)
> +static int pmu_validate_hw_event(unsigned long hw_event)
>  {
>  	u8 ev_source = CCI_PMU_EVENT_SOURCE(hw_event);
>  	u8 ev_code = CCI_PMU_EVENT_CODE(hw_event);
>  	int if_type;
>  
> +	if (hw_event & ~CCI_PMU_EVENT_MASK)
> +		return -ENOENT;

Given that you want to build this for arm64, shouldn't CCI_PMU_EVENT_MASK
be an unsigned long too (i.e. 0xffUL)? Otherwise you won't detect set bits
in the upper word here.

Will
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