From: Andrew Jones <drjones@redhat.com>
To: Steven Price <steven.price@arm.com>
Cc: "Mark Rutland" <mark.rutland@arm.com>,
kvm@vger.kernel.org, "Radim Krčmář" <rkrcmar@redhat.com>,
"Marc Zyngier" <maz@kernel.org>,
"Suzuki K Pouloze" <suzuki.poulose@arm.com>,
linux-doc@vger.kernel.org, "Russell King" <linux@armlinux.org.uk>,
linux-kernel@vger.kernel.org, "James Morse" <james.morse@arm.com>,
"Julien Thierry" <julien.thierry.kdev@gmail.com>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Will Deacon" <will@kernel.org>,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v5 05/10] KVM: arm64: Support stolen time reporting via shared structure
Date: Fri, 4 Oct 2019 11:51:16 +0200 [thread overview]
Message-ID: <20191004095116.a6bi46y76chik3kd@kamzik.brq.redhat.com> (raw)
In-Reply-To: <b107c1ca-6804-dc47-af25-fcd0b201472f@arm.com>
On Fri, Oct 04, 2019 at 10:13:40AM +0100, Steven Price wrote:
> On 04/10/2019 08:03, Andrew Jones wrote:
> > On Thu, Oct 03, 2019 at 03:22:35PM +0200, Andrew Jones wrote:
> >> On Wed, Oct 02, 2019 at 03:50:32PM +0100, Steven Price wrote:
> >>> +int kvm_update_stolen_time(struct kvm_vcpu *vcpu, bool init)
> >>> +{
> >>> + struct kvm *kvm = vcpu->kvm;
> >>> + u64 steal;
> >>> + u64 steal_le;
> >>> + u64 offset;
> >>> + int idx;
> >>> + u64 base = vcpu->arch.steal.base;
> >>> +
> >>> + if (base == GPA_INVALID)
> >>> + return -ENOTSUPP;
> >>> +
> >>> + /* Let's do the local bookkeeping */
> >>> + steal = vcpu->arch.steal.steal;
> >>> + steal += current->sched_info.run_delay - vcpu->arch.steal.last_steal;
> >>> + vcpu->arch.steal.last_steal = current->sched_info.run_delay;
> >>> + vcpu->arch.steal.steal = steal;
> >>> +
> >>> + steal_le = cpu_to_le64(steal);
> >>
> >> Agreeing on a byte order for this interface makes sense, but I don't see
> >> it documented anywhere. Is this an SMCCC thing? Because I skimmed some
> >> of those specs and other users too but didn't see anything obvious. Anyway
> >> even if everybody but me knows that all data returned from SMCCC calls
> >> should be LE, it might be nice to document that in the pvtime doc.
>
> A very good point - I'll document this in the Linux document and feed
> that back for DEN0057A.
>
> >
> > I have another [potentially dumb] SMCCC byte order question. If we need
> > to worry about using LE for the members of this structure, then why don't
> > we need to worry about the actual return values of the SMCCC calls? Like
> > the IPA of the structure?
>
> The SMCCC calls pass values in registers. It's only when reading/writing
> these values from/to memory that the endianness actually has any meaning.
>
Ah yes, of course.
Thanks,
drew
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next prev parent reply other threads:[~2019-10-04 9:51 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-02 14:50 [PATCH v5 00/10] arm64: Stolen time support Steven Price
2019-10-02 14:50 ` [PATCH v5 01/10] KVM: arm64: Document PV-time interface Steven Price
2019-10-03 12:19 ` Andrew Jones
2019-10-04 9:00 ` Steven Price
2019-10-02 14:50 ` [PATCH v5 02/10] KVM: arm/arm64: Factor out hypercall handling from PSCI code Steven Price
2019-10-03 12:23 ` Andrew Jones
2019-10-02 14:50 ` [PATCH v5 03/10] KVM: arm64: Implement PV_FEATURES call Steven Price
2019-10-02 14:50 ` [PATCH v5 04/10] KVM: Implement kvm_put_guest() Steven Price
2019-10-02 14:50 ` [PATCH v5 05/10] KVM: arm64: Support stolen time reporting via shared structure Steven Price
2019-10-03 13:22 ` Andrew Jones
2019-10-04 7:03 ` Andrew Jones
2019-10-04 9:13 ` Steven Price
2019-10-04 9:51 ` Andrew Jones [this message]
2019-10-02 14:50 ` [PATCH v5 06/10] KVM: Allow kvm_device_ops to be const Steven Price
2019-10-03 13:23 ` Andrew Jones
2019-10-02 14:50 ` [PATCH v5 07/10] KVM: arm64: Provide VCPU attributes for stolen time Steven Price
2019-10-02 14:50 ` [PATCH v5 08/10] arm/arm64: Provide a wrapper for SMCCC 1.1 calls Steven Price
2019-10-02 14:50 ` [PATCH v5 09/10] arm/arm64: Make use of the SMCCC 1.1 wrapper Steven Price
2019-10-02 14:50 ` [PATCH v5 10/10] arm64: Retrieve stolen time as paravirtualized guest Steven Price
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