KVM Archive on lore.kernel.org
 help / color / Atom feed
From: Marc Zyngier <maz@kernel.org>
To: linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org
Cc: James Morse <james.morse@arm.com>,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>
Subject: [PATCH 0/2] KVM: arm64: Filtering PMU events
Date: Fri, 14 Feb 2020 18:36:13 +0000
Message-ID: <20200214183615.25498-1-maz@kernel.org> (raw)

It is at times necessary to prevent a guest from being able to sample
certain events if multiple CPUs share resources such as a cache level.
In this case, it would be interesting if the VMM could simply prevent
certain events from being counted instead of simply not exposing a PMU.

Given that most events are not architected, there is no easy way
to designate which events shouldn't be counted other than specifying
the raw event number.

Since I have no idea whether it is better to use an event whitelist
or blacklist, the proposed API takes a cue from the x86 version and
allows either allowing or denying counting of ranges of events.
The event space being pretty large (16bits on ARMv8.1), the default
policy is set by the first filter that gets installed (default deny if
we first allow, default allow if we first deny).

The filter state is global to the guest, despite the PMU being per
CPU. I'm not sure whether it would be worth it making it CPU-private.

Anyway, I'd be interesting in comments on how people would use this.
I'll try to push a patch against kvmtool that implement this shortly
(what I have currently is a harcoded set of hacks).

Marc Zyngier (2):
  KVM: arm64: Add PMU event filtering infrastructure
  KVM: arm64: Document PMU filtering API

 Documentation/virt/kvm/devices/vcpu.txt | 28 +++++++++
 arch/arm64/include/asm/kvm_host.h       |  6 ++
 arch/arm64/include/uapi/asm/kvm.h       | 16 ++++++
 virt/kvm/arm/arm.c                      |  2 +
 virt/kvm/arm/pmu.c                      | 76 +++++++++++++++++++++----
 5 files changed, 116 insertions(+), 12 deletions(-)

-- 
2.20.1


             reply index

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-14 18:36 Marc Zyngier [this message]
2020-02-14 18:36 ` [PATCH 1/2] KVM: arm64: Add PMU event filtering infrastructure Marc Zyngier
2020-02-14 22:01   ` Robin Murphy
2020-02-15 10:28     ` Marc Zyngier
2020-02-17 15:33       ` Robin Murphy
2020-02-14 18:36 ` [PATCH 2/2] KVM: arm64: Document PMU filtering API Marc Zyngier
2020-02-15 13:00 ` [PATCH 0/2] KVM: arm64: Filtering PMU events Marc Zyngier

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200214183615.25498-1-maz@kernel.org \
    --to=maz@kernel.org \
    --cc=james.morse@arm.com \
    --cc=julien.thierry.kdev@gmail.com \
    --cc=kvm@vger.kernel.org \
    --cc=kvmarm@lists.cs.columbia.edu \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=suzuki.poulose@arm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

KVM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/kvm/0 kvm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 kvm kvm/ https://lore.kernel.org/kvm \
		kvm@vger.kernel.org
	public-inbox-index kvm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.kvm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git