[Xen-devel] Registering interrupt handler for performance counter overflow

[Eitan Kaplan <e.kaplan@xxxxxxxxxxxx>]

Hi all,

I am a computer engineering student at Columbia University. This is my first time writing to this list (please let me know if this isn't the place for this type of question!).

I am working with a professor on a project to mitigate Spectre and Meltdown (and other similar cache timing side-channel attacks).  We are using Xen and modifying its source as a way of modeling the affect certain potential hardware changes. As part of that project, we need to use the performance counters to generate interrupts at certain microarchitectural events.  I have successfully added into xen/arch/x86/setup.c a few lines to setup the (Intel Sandy Bridge) performance counter control MSRs and set the counter itself to a few below overflow.  All that's missing is a simple interrupt handler that will reset the counter to a few below overflow (and perhaps do some logging).

I am having trouble figuring out how to register my handler in Xen.  I assume that I have to call request_irq(), but I am not sure how to set all the arguments for that call.  Would anyone be able to give me any pointers?  Suggestions or pointers to resources/examples for registering interrupt handlers in Xen would be really helpful!

Alternatively, is there an existing interrupt handler that is already setup for PMC overflow interrupts that I might be able to tweak?

Thank you!

Eitan Kaplan

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