From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Marc Zyngier <maz@kernel.org>
Cc: kvm@vger.kernel.org, Will Deacon <will@kernel.org>,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Subject: Re: REGRESSION: Upgrading host kernel from 5.11 to 5.13 breaks QEMU guests - perf/fw_devlink/kvm
Date: Mon, 20 Sep 2021 10:45:26 +0100 [thread overview]
Message-ID: <YUhYNnwaTt+5oMzh@shell.armlinux.org.uk> (raw)
In-Reply-To: <877dfcwutt.wl-maz@kernel.org>
On Sun, Sep 19, 2021 at 02:36:46PM +0100, Marc Zyngier wrote:
> 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:
kvm [7]: PMU detected and enabled
in the kernel boot log.
Tested-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Thanks.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
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next prev parent reply other threads:[~2021-09-20 9:45 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-18 16:17 REGRESSION: Upgrading host kernel from 5.11 to 5.13 breaks QEMU guests - perf/fw_devlink/kvm Russell King (Oracle)
2021-09-19 13:36 ` Marc Zyngier
2021-09-20 9:45 ` Russell King (Oracle) [this message]
2021-09-20 14:39 ` Andrew Jones
2021-09-20 9:56 ` Will Deacon
2021-09-20 10:23 ` Marc Zyngier
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