Messages in this thread | | | Subject | Re: [PATCH 5/9] perf: Adding sysfs group format attribute for pmu device | From | Peter Zijlstra <> | Date | Wed, 01 Feb 2012 14:36:24 +0100 |
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On Tue, 2012-01-31 at 17:25 -0800, Corey Ashford wrote: > > One other comment that occurs to me is that it would be nice for perf to > know when a supplied value is out of range, or will have undefined > results. For example, a field may be 8 bits wide, but not all 8-bit > values are legal. For example, there may be 208 events, and the codes > may be somehwhat or even very sparsely encoded. So, ideally, a config > field in sysfs might look like this: > > config1:0-7:0x0-0xd8,0xdb-0xe2,0xe4-0xe6 > > This way perf could check for valid values before stuffing them into > registers, and give a good error message to the user. If there is no > restriction field, it would be assumed all of the possible values are valid. > > I think the kernel code needs to check for bad values as well, because > people can bypass the restrictions exposed by sysfs and use the > perf_events API directly.
Define bad? The only case where perf cares (from a kernel pov) is when it can make the hardware melt and similar things. Programming the PMU in a non-nonsensical but non-destructive way is fine, you get what you ask for.
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