From: Sean Christopherson <seanjc@google.com>
To: Oliver Upton <oupton@google.com>
Cc: Marc Zyngier <maz@kernel.org>,
kvm@vger.kernel.org, Peter Shier <pshier@google.com>,
kvmarm@lists.cs.columbia.edu
Subject: Re: [PATCH v2 05/11] KVM: arm64: Defer WFI emulation as a requested event
Date: Thu, 30 Sep 2021 18:08:32 +0000 [thread overview]
Message-ID: <YVX9IOb1vyoJowQl@google.com> (raw)
In-Reply-To: <CAOQ_QsjXs8sF+QY0NrSVBvO4xump7CttBU3et6V3O_hNYmCSig@mail.gmail.com>
On Thu, Sep 30, 2021, Oliver Upton wrote:
> On Thu, Sep 30, 2021 at 10:09 AM Sean Christopherson <seanjc@google.com> wrote:
> > Unlike PSCI power-off, WFI isn't cross-vCPU, thus there's no hard requirement
> > for using a request. And KVM_REQ_SLEEP also has an additional guard in that it
> > doesn't enter rcuwait if power_off (or pause) was cleared after the request was
> > made, e.g. if userspace stuffed vCPU state and set the vCPU RUNNABLE.
>
> Yeah, I don't think the punt is necessary for anything but the case
> where userspace sets the MP state to request WFI behavior. A helper
> method amongst all WFI cases is sufficient, and using the deferral for
> everything is a change in behavior.
Is there an actual use case for letting userspace request WFI behavior?
WARNING: multiple messages have this Message-ID (diff)
From: Sean Christopherson <seanjc@google.com>
To: Oliver Upton <oupton@google.com>
Cc: Marc Zyngier <maz@kernel.org>, Peter Shier <pshier@google.com>,
kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org
Subject: Re: [PATCH v2 05/11] KVM: arm64: Defer WFI emulation as a requested event
Date: Thu, 30 Sep 2021 18:08:32 +0000 [thread overview]
Message-ID: <YVX9IOb1vyoJowQl@google.com> (raw)
In-Reply-To: <CAOQ_QsjXs8sF+QY0NrSVBvO4xump7CttBU3et6V3O_hNYmCSig@mail.gmail.com>
On Thu, Sep 30, 2021, Oliver Upton wrote:
> On Thu, Sep 30, 2021 at 10:09 AM Sean Christopherson <seanjc@google.com> wrote:
> > Unlike PSCI power-off, WFI isn't cross-vCPU, thus there's no hard requirement
> > for using a request. And KVM_REQ_SLEEP also has an additional guard in that it
> > doesn't enter rcuwait if power_off (or pause) was cleared after the request was
> > made, e.g. if userspace stuffed vCPU state and set the vCPU RUNNABLE.
>
> Yeah, I don't think the punt is necessary for anything but the case
> where userspace sets the MP state to request WFI behavior. A helper
> method amongst all WFI cases is sufficient, and using the deferral for
> everything is a change in behavior.
Is there an actual use case for letting userspace request WFI behavior?
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next prev parent reply other threads:[~2021-09-30 18:08 UTC|newest]
Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-23 19:15 [PATCH v2 00/11] KVM: arm64: Implement PSCI SYSTEM_SUSPEND support Oliver Upton
2021-09-23 19:15 ` Oliver Upton
2021-09-23 19:16 ` [PATCH v2 01/11] KVM: arm64: Drop unused vcpu param to kvm_psci_valid_affinity() Oliver Upton
2021-09-23 19:16 ` Oliver Upton
2021-10-01 3:50 ` Reiji Watanabe
2021-10-01 3:50 ` Reiji Watanabe
2021-10-05 13:22 ` Andrew Jones
2021-10-05 13:22 ` Andrew Jones
2021-09-23 19:16 ` [PATCH v2 02/11] KVM: arm64: Clean up SMC64 PSCI filtering for AArch32 guests Oliver Upton
2021-09-23 19:16 ` Oliver Upton
2021-10-01 3:56 ` Reiji Watanabe
2021-10-01 3:56 ` Reiji Watanabe
2021-10-05 13:23 ` Andrew Jones
2021-10-05 13:23 ` Andrew Jones
2021-09-23 19:16 ` [PATCH v2 03/11] KVM: arm64: Encapsulate reset request logic in a helper function Oliver Upton
2021-09-23 19:16 ` Oliver Upton
2021-10-01 6:04 ` Reiji Watanabe
2021-10-01 6:04 ` Reiji Watanabe
2021-10-01 16:10 ` Oliver Upton
2021-10-01 16:10 ` Oliver Upton
2021-10-05 13:33 ` Andrew Jones
2021-10-05 13:33 ` Andrew Jones
2021-10-05 15:05 ` Oliver Upton
2021-10-05 15:05 ` Oliver Upton
2021-10-05 19:01 ` Andrew Jones
2021-10-05 19:01 ` Andrew Jones
2021-10-13 4:48 ` Reiji Watanabe
2021-10-13 4:48 ` Reiji Watanabe
2021-10-05 13:35 ` Andrew Jones
2021-10-05 13:35 ` Andrew Jones
2021-09-23 19:16 ` [PATCH v2 04/11] KVM: arm64: Rename the KVM_REQ_SLEEP handler Oliver Upton
2021-09-23 19:16 ` Oliver Upton
2021-10-05 13:34 ` Andrew Jones
2021-10-05 13:34 ` Andrew Jones
2021-09-23 19:16 ` [PATCH v2 05/11] KVM: arm64: Defer WFI emulation as a requested event Oliver Upton
2021-09-23 19:16 ` Oliver Upton
2021-09-30 10:50 ` Marc Zyngier
2021-09-30 10:50 ` Marc Zyngier
2021-09-30 17:09 ` Sean Christopherson
2021-09-30 17:09 ` Sean Christopherson
2021-09-30 17:32 ` Oliver Upton
2021-09-30 17:32 ` Oliver Upton
2021-09-30 18:08 ` Sean Christopherson [this message]
2021-09-30 18:08 ` Sean Christopherson
2021-09-30 21:57 ` Oliver Upton
2021-09-30 21:57 ` Oliver Upton
2021-10-01 13:57 ` Marc Zyngier
2021-10-01 13:57 ` Marc Zyngier
2021-09-23 19:16 ` [PATCH v2 06/11] KVM: arm64: Add support for SYSTEM_SUSPEND PSCI call Oliver Upton
2021-09-23 19:16 ` Oliver Upton
2021-09-30 12:29 ` Marc Zyngier
2021-09-30 12:29 ` Marc Zyngier
2021-09-30 17:19 ` Sean Christopherson
2021-09-30 17:19 ` Sean Christopherson
2021-09-30 17:35 ` Oliver Upton
2021-09-30 17:35 ` Oliver Upton
2021-09-30 17:40 ` Oliver Upton
2021-09-30 17:40 ` Oliver Upton
2021-10-01 14:02 ` Marc Zyngier
2021-10-01 14:02 ` Marc Zyngier
2021-10-05 16:02 ` Oliver Upton
2021-10-05 16:02 ` Oliver Upton
2021-09-23 19:16 ` [PATCH v2 07/11] selftests: KVM: Rename psci_cpu_on_test to psci_test Oliver Upton
2021-09-23 19:16 ` Oliver Upton
2021-10-05 13:36 ` Andrew Jones
2021-10-05 13:36 ` Andrew Jones
2021-09-23 19:16 ` [PATCH v2 08/11] selftests: KVM: Create helper for making SMCCC calls Oliver Upton
2021-09-23 19:16 ` Oliver Upton
2021-10-05 13:39 ` Andrew Jones
2021-10-05 13:39 ` Andrew Jones
2021-09-23 19:16 ` [PATCH v2 09/11] selftests: KVM: Use KVM_SET_MP_STATE to power off vCPU in psci_test Oliver Upton
2021-09-23 19:16 ` Oliver Upton
2021-09-23 19:16 ` [PATCH v2 10/11] selftests: KVM: Refactor psci_test to make it amenable to new tests Oliver Upton
2021-09-23 19:16 ` Oliver Upton
2021-10-05 13:45 ` Andrew Jones
2021-10-05 13:45 ` Andrew Jones
2021-10-05 14:54 ` Oliver Upton
2021-10-05 14:54 ` Oliver Upton
2021-10-05 19:05 ` Andrew Jones
2021-10-05 19:05 ` Andrew Jones
2021-09-23 19:16 ` [PATCH v2 11/11] selftests: KVM: Test SYSTEM_SUSPEND PSCI call Oliver Upton
2021-09-23 19:16 ` Oliver Upton
2021-10-05 13:49 ` Andrew Jones
2021-10-05 13:49 ` Andrew Jones
2021-10-05 15:07 ` Oliver Upton
2021-10-05 15:07 ` Oliver Upton
2021-09-23 20:15 ` [PATCH v2 00/11] KVM: arm64: Implement PSCI SYSTEM_SUSPEND support Oliver Upton
2021-09-23 20:15 ` Oliver Upton
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