All of lore.kernel.org
 help / color / mirror / Atom feed
From: Marc Zyngier <maz@kernel.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Reiji Watanabe <reijiw@google.com>,
	Oliver Upton <oliver.upton@linux.dev>,
	Will Deacon <will@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	kvmarm@lists.linux.dev, kvm@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	James Morse <james.morse@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Zenghui Yu <yuzenghui@huawei.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Ricardo Koller <ricarkol@google.com>,
	Jing Zhang <jingzhangos@google.com>,
	Raghavendra Rao Anata <rananta@google.com>,
	Shaoqin Huang <shahuang@redhat.com>,
	Rob Herring <robh@kernel.org>
Subject: Re: [PATCH v2 2/2] KVM: arm64: PMU: Don't overwrite PMUSERENR with vcpu loaded
Date: Wed, 12 Apr 2023 11:22:29 +0100	[thread overview]
Message-ID: <86v8i1l7ru.wl-maz@kernel.org> (raw)
In-Reply-To: <ZDZ3xbSePtOD3CSX@FVFF77S0Q05N>

On Wed, 12 Apr 2023 10:20:05 +0100,
Mark Rutland <mark.rutland@arm.com> wrote:
> 
> On Tue, Apr 11, 2023 at 10:14:10PM -0700, Reiji Watanabe wrote:
> > Uh, right, interrupts are not masked during those windows...
> > 
> > What I am currently considering on this would be disabling
> > IRQs while manipulating the register, and introducing a new flag
> > to indicate whether the PMUSERENR for the guest EL0 is loaded,
> > and having kvm_set_pmuserenr() check the new flag.
> > 
> > The code would be something like below (local_irq_save/local_irq_restore
> > needs to be excluded for NVHE though).

It shouldn't need to be excluded. It should be fairly harmless, unless
I'm missing something really obvious?

> > 
> > What do you think ?
> 
> I'm happy with that; it doesn't change the arm_pmu side of the interface and it
> looks good from a functional perspective.
> 
> I'll have to leave it to Marc and Oliver to say whether they're happy with the
> KVM side.

This looks OK to me. My only ask would be to have a small comment in
the __{de}activate_traps_common() functions to say what this protects
against, because I'll page it out within minutes.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Reiji Watanabe <reijiw@google.com>,
	Oliver Upton <oliver.upton@linux.dev>,
	Will Deacon <will@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	kvmarm@lists.linux.dev, kvm@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	James Morse <james.morse@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Zenghui Yu <yuzenghui@huawei.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Ricardo Koller <ricarkol@google.com>,
	Jing Zhang <jingzhangos@google.com>,
	Raghavendra Rao Anata <rananta@google.com>,
	Shaoqin Huang <shahuang@redhat.com>,
	Rob Herring <robh@kernel.org>
Subject: Re: [PATCH v2 2/2] KVM: arm64: PMU: Don't overwrite PMUSERENR with vcpu loaded
Date: Wed, 12 Apr 2023 11:22:29 +0100	[thread overview]
Message-ID: <86v8i1l7ru.wl-maz@kernel.org> (raw)
In-Reply-To: <ZDZ3xbSePtOD3CSX@FVFF77S0Q05N>

On Wed, 12 Apr 2023 10:20:05 +0100,
Mark Rutland <mark.rutland@arm.com> wrote:
> 
> On Tue, Apr 11, 2023 at 10:14:10PM -0700, Reiji Watanabe wrote:
> > Uh, right, interrupts are not masked during those windows...
> > 
> > What I am currently considering on this would be disabling
> > IRQs while manipulating the register, and introducing a new flag
> > to indicate whether the PMUSERENR for the guest EL0 is loaded,
> > and having kvm_set_pmuserenr() check the new flag.
> > 
> > The code would be something like below (local_irq_save/local_irq_restore
> > needs to be excluded for NVHE though).

It shouldn't need to be excluded. It should be fairly harmless, unless
I'm missing something really obvious?

> > 
> > What do you think ?
> 
> I'm happy with that; it doesn't change the arm_pmu side of the interface and it
> looks good from a functional perspective.
> 
> I'll have to leave it to Marc and Oliver to say whether they're happy with the
> KVM side.

This looks OK to me. My only ask would be to have a small comment in
the __{de}activate_traps_common() functions to say what this protects
against, because I'll page it out within minutes.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2023-04-12 10:22 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-04-08  3:47 [PATCH v2 0/2] KVM: arm64: PMU: Correct the handling of PMUSERENR_EL0 Reiji Watanabe
2023-04-08  3:47 ` Reiji Watanabe
2023-04-08  3:47 ` [PATCH v2 1/2] KVM: arm64: PMU: Restore the host's PMUSERENR_EL0 Reiji Watanabe
2023-04-08  3:47   ` Reiji Watanabe
2023-04-08  3:47 ` [PATCH v2 2/2] KVM: arm64: PMU: Don't overwrite PMUSERENR with vcpu loaded Reiji Watanabe
2023-04-08  3:47   ` Reiji Watanabe
2023-04-11  9:33   ` Mark Rutland
2023-04-11  9:33     ` Mark Rutland
2023-04-12  5:14     ` Reiji Watanabe
2023-04-12  5:14       ` Reiji Watanabe
2023-04-12  9:20       ` Mark Rutland
2023-04-12  9:20         ` Mark Rutland
2023-04-12 10:22         ` Marc Zyngier [this message]
2023-04-12 10:22           ` Marc Zyngier
2023-04-13  0:07           ` Reiji Watanabe
2023-04-13  0:07             ` Reiji Watanabe
2023-04-13  8:56             ` Marc Zyngier
2023-04-13  8:56               ` Marc Zyngier
2023-04-15  3:11               ` Reiji Watanabe
2023-04-15  3:11                 ` Reiji Watanabe
2023-04-08  9:04 ` [PATCH v2 0/2] KVM: arm64: PMU: Correct the handling of PMUSERENR_EL0 Marc Zyngier
2023-04-08  9:04   ` Marc Zyngier
2023-04-11 11:24   ` Will Deacon
2023-04-11 11:24     ` Will Deacon
2023-04-12 10:29     ` Marc Zyngier
2023-04-12 10:29       ` 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=86v8i1l7ru.wl-maz@kernel.org \
    --to=maz@kernel.org \
    --cc=alexandru.elisei@arm.com \
    --cc=catalin.marinas@arm.com \
    --cc=james.morse@arm.com \
    --cc=jingzhangos@google.com \
    --cc=kvm@vger.kernel.org \
    --cc=kvmarm@lists.linux.dev \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=mark.rutland@arm.com \
    --cc=oliver.upton@linux.dev \
    --cc=pbonzini@redhat.com \
    --cc=rananta@google.com \
    --cc=reijiw@google.com \
    --cc=ricarkol@google.com \
    --cc=robh@kernel.org \
    --cc=shahuang@redhat.com \
    --cc=suzuki.poulose@arm.com \
    --cc=will@kernel.org \
    --cc=yuzenghui@huawei.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
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.