linux-kernel - Re: [PATCH v15 7/9] ptp: arm/arm64: Enable ptp

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <5dc5480d125ace6566ae616206c3ce3f@kernel.org>
Date:   Tue, 24 Nov 2020 09:04:57 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Jianyong Wu <Jianyong.Wu@....com>
Cc:     netdev@...r.kernel.org, yangbo.lu@....com, john.stultz@...aro.org,
        tglx@...utronix.de, pbonzini@...hat.com,
        sean.j.christopherson@...el.com, richardcochran@...il.com,
        Mark Rutland <Mark.Rutland@....com>, will@...nel.org,
        Suzuki Poulose <Suzuki.Poulose@....com>,
        Andre Przywara <Andre.Przywara@....com>,
        Steven Price <Steven.Price@....com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
        Steve Capper <Steve.Capper@....com>,
        Justin He <Justin.He@....com>, nd <nd@....com>
Subject: Re: [PATCH v15 7/9] ptp: arm/arm64: Enable ptp_kvm for arm/arm64

Jianyong,

On 2020-11-24 05:37, Jianyong Wu wrote:
> Hi Marc,

[...]

>> > +
>> 	arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_PTP_FU
>> NC_ID,
>> > +			     ARM_PTP_NONE_COUNTER, &hvc_res);
>> 
>> I really don't see the need to use a non-architectural counter ID.
>> Using the virtual counter ID should just be fine, and shouldn't lead 
>> to any
>> issue.
>> 
> 
>> Am I missing something?
> 
> In this function, no counter data is needed. If virtual counter ID is
> used here, user may be confused with why we get virtual counter
> data and do nothing with it. So I explicitly add a new "NONE" counter
> ID to make it clear.
> 
> WDYT?

ITIABI (I Think It's A Bad Idea). There are two counters, and the API
allows to retrieve the data for any of these two. If the "user" doesn't
want to do anything with the data, that's their problem.

Here, you can just sue the virtual counter, and that will give you the
exact same semantic, without inventing non-architectural state.

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...