linux-kernel - Re: [PATCH] x86: convert x86_platform

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Message-ID: <9eed0fcb-ec0b-9a1a-934f-e79a4b428e14@redhat.com>
Date:   Mon, 16 Oct 2017 14:21:22 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        y2038 Mailman List <y2038@...ts.linaro.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Juergen Gross <jgross@...e.com>,
        Marcos Paulo de Souza <marcos.souza.org@...il.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        John Stultz <john.stultz@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kvm@...r.kernel.org, xen-devel <xen-devel@...ts.xenproject.org>
Subject: Re: [PATCH] x86: convert x86_platform_ops to timespec64

On 16/10/2017 14:16, Arnd Bergmann wrote:
> On Mon, Oct 16, 2017 at 2:08 PM, Paolo Bonzini <pbonzini@...hat.com> wrote:
>> On 16/10/2017 10:11, Arnd Bergmann wrote:
>>> Thanks!
>>>
>>> Since you've looked at it overall, do you have an opinion on the question
>>> how to fix the PV interface to deal with the pvclock_wall_clock overflow?
>>
>> It has to be done separately for each hypervisor.
>>
>> In KVM, for example, it is probably best to abandon
>> pvclock_read_wallclock altogether, and instead use the recently
>> introduced KVM_HC_CLOCK_PAIRING hypercall.  drivers/ptp/ptp_kvm.c is
>> already using it and it's y2106 safe.
> 
> Right, makes sense. I see that this interface is currently implemented
> only for 64-bit x86 in kvm_emulate_hypercall(). Could this be extended
> to x86-32 and the non-x86 architectures as well?

Yes, it could be implemented for x86-32 too.  The whole pvclock concept
however is specific to x86.

Paolo