From: Marcelo Tosatti <mtosatti@redhat.com>
To: Oliver Upton <oupton@google.com>
Cc: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Marc Zyngier <maz@kernel.org>, Peter Shier <pshier@google.com>,
Jim Mattson <jmattson@google.com>,
David Matlack <dmatlack@google.com>,
Ricardo Koller <ricarkol@google.com>,
Jing Zhang <jingzhangos@google.com>,
Raghavendra Rao Anata <rananta@google.com>,
James Morse <james.morse@arm.com>,
Alexandru Elisei <Alexandru.Elisei@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
linux-arm-kernel@lists.infradead.org,
Andrew Jones <drjones@redhat.com>, Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>
Subject: Re: [PATCH v7 6/6] KVM: x86: Expose TSC offset controls to userspace
Date: Thu, 26 Aug 2021 09:48:36 -0300 [thread overview]
Message-ID: <20210826124836.GA155749@fuller.cnet> (raw)
In-Reply-To: <CAOQ_Qsj_MfRNRRSK1UswsfBw4c9ugSW6tKXNua=3O78sHEonvA@mail.gmail.com>
On Mon, Aug 23, 2021 at 01:56:30PM -0700, Oliver Upton wrote:
> Paolo,
>
> On Sun, Aug 15, 2021 at 5:11 PM Oliver Upton <oupton@google.com> wrote:
> >
> > To date, VMM-directed TSC synchronization and migration has been a bit
> > messy. KVM has some baked-in heuristics around TSC writes to infer if
> > the VMM is attempting to synchronize. This is problematic, as it depends
> > on host userspace writing to the guest's TSC within 1 second of the last
> > write.
> >
> > A much cleaner approach to configuring the guest's views of the TSC is to
> > simply migrate the TSC offset for every vCPU. Offsets are idempotent,
> > and thus not subject to change depending on when the VMM actually
> > reads/writes values from/to KVM. The VMM can then read the TSC once with
> > KVM_GET_CLOCK to capture a (realtime, host_tsc) pair at the instant when
> > the guest is paused.
> >
> > Cc: David Matlack <dmatlack@google.com>
> > Cc: Sean Christopherson <seanjc@google.com>
> > Signed-off-by: Oliver Upton <oupton@google.com>
>
> Could you please squash the following into this patch? We need to
> advertise KVM_CAP_VCPU_ATTRIBUTES to userspace. Otherwise, happy to
> resend.
>
> Thanks,
> Oliver
Oliver,
Is there QEMU support for this, or are you using your own
userspace with this?
WARNING: multiple messages have this Message-ID (diff)
From: Marcelo Tosatti <mtosatti@redhat.com>
To: Oliver Upton <oupton@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
kvm@vger.kernel.org, Will Deacon <will@kernel.org>,
Marc Zyngier <maz@kernel.org>, Peter Shier <pshier@google.com>,
Sean Christopherson <seanjc@google.com>,
David Matlack <dmatlack@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org,
Jim Mattson <jmattson@google.com>
Subject: Re: [PATCH v7 6/6] KVM: x86: Expose TSC offset controls to userspace
Date: Thu, 26 Aug 2021 09:48:36 -0300 [thread overview]
Message-ID: <20210826124836.GA155749@fuller.cnet> (raw)
In-Reply-To: <CAOQ_Qsj_MfRNRRSK1UswsfBw4c9ugSW6tKXNua=3O78sHEonvA@mail.gmail.com>
On Mon, Aug 23, 2021 at 01:56:30PM -0700, Oliver Upton wrote:
> Paolo,
>
> On Sun, Aug 15, 2021 at 5:11 PM Oliver Upton <oupton@google.com> wrote:
> >
> > To date, VMM-directed TSC synchronization and migration has been a bit
> > messy. KVM has some baked-in heuristics around TSC writes to infer if
> > the VMM is attempting to synchronize. This is problematic, as it depends
> > on host userspace writing to the guest's TSC within 1 second of the last
> > write.
> >
> > A much cleaner approach to configuring the guest's views of the TSC is to
> > simply migrate the TSC offset for every vCPU. Offsets are idempotent,
> > and thus not subject to change depending on when the VMM actually
> > reads/writes values from/to KVM. The VMM can then read the TSC once with
> > KVM_GET_CLOCK to capture a (realtime, host_tsc) pair at the instant when
> > the guest is paused.
> >
> > Cc: David Matlack <dmatlack@google.com>
> > Cc: Sean Christopherson <seanjc@google.com>
> > Signed-off-by: Oliver Upton <oupton@google.com>
>
> Could you please squash the following into this patch? We need to
> advertise KVM_CAP_VCPU_ATTRIBUTES to userspace. Otherwise, happy to
> resend.
>
> Thanks,
> Oliver
Oliver,
Is there QEMU support for this, or are you using your own
userspace with this?
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
WARNING: multiple messages have this Message-ID (diff)
From: Marcelo Tosatti <mtosatti@redhat.com>
To: Oliver Upton <oupton@google.com>
Cc: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Marc Zyngier <maz@kernel.org>, Peter Shier <pshier@google.com>,
Jim Mattson <jmattson@google.com>,
David Matlack <dmatlack@google.com>,
Ricardo Koller <ricarkol@google.com>,
Jing Zhang <jingzhangos@google.com>,
Raghavendra Rao Anata <rananta@google.com>,
James Morse <james.morse@arm.com>,
Alexandru Elisei <Alexandru.Elisei@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
linux-arm-kernel@lists.infradead.org,
Andrew Jones <drjones@redhat.com>, Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>
Subject: Re: [PATCH v7 6/6] KVM: x86: Expose TSC offset controls to userspace
Date: Thu, 26 Aug 2021 09:48:36 -0300 [thread overview]
Message-ID: <20210826124836.GA155749@fuller.cnet> (raw)
In-Reply-To: <CAOQ_Qsj_MfRNRRSK1UswsfBw4c9ugSW6tKXNua=3O78sHEonvA@mail.gmail.com>
On Mon, Aug 23, 2021 at 01:56:30PM -0700, Oliver Upton wrote:
> Paolo,
>
> On Sun, Aug 15, 2021 at 5:11 PM Oliver Upton <oupton@google.com> wrote:
> >
> > To date, VMM-directed TSC synchronization and migration has been a bit
> > messy. KVM has some baked-in heuristics around TSC writes to infer if
> > the VMM is attempting to synchronize. This is problematic, as it depends
> > on host userspace writing to the guest's TSC within 1 second of the last
> > write.
> >
> > A much cleaner approach to configuring the guest's views of the TSC is to
> > simply migrate the TSC offset for every vCPU. Offsets are idempotent,
> > and thus not subject to change depending on when the VMM actually
> > reads/writes values from/to KVM. The VMM can then read the TSC once with
> > KVM_GET_CLOCK to capture a (realtime, host_tsc) pair at the instant when
> > the guest is paused.
> >
> > Cc: David Matlack <dmatlack@google.com>
> > Cc: Sean Christopherson <seanjc@google.com>
> > Signed-off-by: Oliver Upton <oupton@google.com>
>
> Could you please squash the following into this patch? We need to
> advertise KVM_CAP_VCPU_ATTRIBUTES to userspace. Otherwise, happy to
> resend.
>
> Thanks,
> Oliver
Oliver,
Is there QEMU support for this, or are you using your own
userspace with this?
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-08-26 12:48 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-16 0:11 [PATCH v7 0/6] KVM: x86: Add idempotent controls for migrating system counter state Oliver Upton
2021-08-16 0:11 ` Oliver Upton
2021-08-16 0:11 ` Oliver Upton
2021-08-16 0:11 ` [PATCH v7 1/6] KVM: x86: Fix potential race in KVM_GET_CLOCK Oliver Upton
2021-08-16 0:11 ` Oliver Upton
2021-08-16 0:11 ` Oliver Upton
2021-08-19 18:24 ` Marcelo Tosatti
2021-08-19 18:24 ` Marcelo Tosatti
2021-08-19 18:24 ` Marcelo Tosatti
2021-08-20 18:22 ` Oliver Upton
2021-08-20 18:22 ` Oliver Upton
2021-08-20 18:22 ` Oliver Upton
2021-08-16 0:11 ` [PATCH v7 2/6] KVM: x86: Create helper methods for KVM_{GET,SET}_CLOCK ioctls Oliver Upton
2021-08-16 0:11 ` Oliver Upton
2021-08-16 0:11 ` Oliver Upton
2021-08-16 0:11 ` [PATCH v7 3/6] KVM: x86: Report host tsc and realtime values in KVM_GET_CLOCK Oliver Upton
2021-08-16 0:11 ` Oliver Upton
2021-08-16 0:11 ` Oliver Upton
2021-08-20 12:46 ` Marcelo Tosatti
2021-08-20 12:46 ` Marcelo Tosatti
2021-08-20 12:46 ` Marcelo Tosatti
2021-09-24 8:30 ` Paolo Bonzini
2021-09-24 8:30 ` Paolo Bonzini
2021-09-24 8:30 ` Paolo Bonzini
2021-08-16 0:11 ` [PATCH v7 4/6] KVM: x86: Take the pvclock sync lock behind the tsc_write_lock Oliver Upton
2021-08-16 0:11 ` Oliver Upton
2021-08-16 0:11 ` Oliver Upton
2021-09-02 19:22 ` Sean Christopherson
2021-09-02 19:22 ` Sean Christopherson
2021-09-02 19:22 ` Sean Christopherson
2021-08-16 0:11 ` [PATCH v7 5/6] KVM: x86: Refactor tsc synchronization code Oliver Upton
2021-08-16 0:11 ` Oliver Upton
2021-08-16 0:11 ` Oliver Upton
2021-09-02 19:21 ` Sean Christopherson
2021-09-02 19:21 ` Sean Christopherson
2021-09-02 19:21 ` Sean Christopherson
2021-09-02 19:41 ` Oliver Upton
2021-09-02 19:41 ` Oliver Upton
2021-09-02 19:41 ` Oliver Upton
2021-09-24 9:28 ` Paolo Bonzini
2021-09-24 9:28 ` Paolo Bonzini
2021-09-24 9:28 ` Paolo Bonzini
2021-08-16 0:11 ` [PATCH v7 6/6] KVM: x86: Expose TSC offset controls to userspace Oliver Upton
2021-08-16 0:11 ` Oliver Upton
2021-08-16 0:11 ` Oliver Upton
2021-08-23 20:56 ` Oliver Upton
2021-08-23 20:56 ` Oliver Upton
2021-08-23 20:56 ` Oliver Upton
2021-08-26 12:48 ` Marcelo Tosatti [this message]
2021-08-26 12:48 ` Marcelo Tosatti
2021-08-26 12:48 ` Marcelo Tosatti
2021-08-26 20:27 ` Oliver Upton
2021-08-26 20:27 ` Oliver Upton
2021-08-26 20:27 ` Oliver Upton
2021-08-29 8:25 ` Paolo Bonzini
2021-09-02 19:23 ` [PATCH v7 0/6] KVM: x86: Add idempotent controls for migrating system counter state Sean Christopherson
2021-09-02 19:23 ` Sean Christopherson
2021-09-02 19:23 ` Sean Christopherson
2021-09-02 19:45 ` Oliver Upton
2021-09-02 19:45 ` Oliver Upton
2021-09-02 19:45 ` Oliver Upton
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