From: Marc Zyngier <maz@kernel.org>
To: Qian Cai <qcai@redhat.com>
Cc: linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu, kernel-team@android.com,
Stephen Rothwell <sfr@canb.auug.org.au>,
Linux Next Mailing List <linux-next@vger.kernel.org>,
Alexandru Elisei <alexandru.elisei@arm.com>
Subject: Re: [PATCH] KVM: arm64: Don't access PMCR_EL0 when no PMU is available
Date: Mon, 04 Jan 2021 19:32:41 +0000 [thread overview]
Message-ID: <81607700b5de4860a6f281c68ee17669@kernel.org> (raw)
In-Reply-To: <22cd2b3e8b8b278f110a3540755583efee7189fd.camel@redhat.com>
On 2021-01-04 18:42, Qian Cai wrote:
> On Mon, 2021-01-04 at 18:26 +0000, Marc Zyngier wrote:
>> What I'm suggesting is this [1], which is to get rid of KVM_ARM_PMU
>> completely. At least, the kernel configuration will be consistent.
>>
>
> Do you have a patch for CONFIG_KVM to select HW_PERF_EVENTS then? I
> could cook
> one if not.
I don't think there should be such a patch. People do disable
HW_PERF_EVENTS in production in some cases, and we should
honor that. All I am trying to guarantee at the moment is
that the KVM configuration is consistent, as I believe that's
what broke in your particular case.
What needs doing is to hide the PMU registers from userspace
when no PMU is configured, or even available. I'll try and post
something to that effect tomorrow (hey, I'm still officially
on holiday...).
M.
--
Jazz is not dead. It just smells funny...
prev parent reply other threads:[~2021-01-04 19:33 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20201210083059.1277162-1-maz@kernel.org>
2021-01-04 15:47 ` [PATCH] KVM: arm64: Don't access PMCR_EL0 when no PMU is available Qian Cai
2021-01-04 16:08 ` Marc Zyngier
2021-01-04 16:22 ` Qian Cai
2021-01-04 16:27 ` Marc Zyngier
2021-01-04 18:20 ` Qian Cai
2021-01-04 18:26 ` Marc Zyngier
2021-01-04 18:42 ` Qian Cai
2021-01-04 19:32 ` Marc Zyngier [this message]
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