On Mon, Sep 20, 2021 at 10:45:26AM +0100, Russell King (Oracle) wrote:

On Sun, Sep 19, 2021 at 02:36:46PM +0100, Marc Zyngier wrote:

quoted

Urgh. That's a bummer. T1he PMU driver only comes up once it has found
its interrupt controller, which on the Armada 8040 is not the GIC, but
some weird thing on the side that doesn't actually serve any real
purpose. On HW where the PMU is directly wired into the GIC, it all
works fine, though by luck rather than by design.

Anyway, rant over. This is a bug that needs addressing so that KVM can
initialise correctly irrespective of the probing order. This probably
means that the static key controlling KVM's behaviour wrt the PMU must
be controlled by the PMU infrastructure itself, rather than KVM trying
to probe for it.

Can you please give the following hack a go (on top of 5.15-rc1)? I've
briefly tested it on my McBin, and it did the trick. I've also tested
it on the M1 (which really doesn't have an architectural PMU) to
verify that it was correctly failing.

My test program that derives the number of registers qemu uses now
reports 236 registers again and I see:

Hi Russell,

You may be interested in kvm selftests and this one[1] in particular.

[1] tools/testing/selftests/kvm/aarch64/get-reg-list.c

Thanks,
drew

kvm [7]: PMU detected and enabled

in the kernel boot log.

Tested-by: Russell King (Oracle) <redacted>

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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