Hey Drew!
On 09.09.20 08:25, Andrew Jones wrote:
On Tue, Sep 08, 2020 at 10:57:30PM +0200, Alexander Graf wrote:
We currently pass through the number of PMU counters that we have available
in hardware to guests. So if my host supports 10 concurrently active PMU
counters, my guest will be able to spawn 10 counters as well.
This is undesireable if we also want to use the PMU on the host for
monitoring. In that case, we want to split the PMU between guest and
host.
To help that case, let's add a PMU attr that allows us to limit the number
of PMU counters that we expose. With this patch in place, user space can
keep some counters free for host use.
Hi Alex,
Is there any reason to use the device API instead of just giving the user
control over the necessary PMCR_EL0 bits through set/get-one-reg?
I mostly used the attr interface because I was in that particular mental
mode after looking at the filtering bits :).
Today, the PMCR_EL0 register gets reset implicitly on every vcpu reset
call. How would we persist the counter field across resets? Would we in
the first place?
I'm slightly hazy how the ONE_REG API would look like here. Do you have
recommendations?
Alex
Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879
