linux-kernel - Re: [PATCH 2/5] x86, vdso, pvclock: Simplify and speed up the vdso pvclock reader

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Message-ID: <CALCETrX=MFYDzcki-2EvKwxUCG-e9yZFJx4NZS_becPG7XwvqA@mail.gmail.com>
Date:	Fri, 11 Dec 2015 10:03:24 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	Ingo Molnar <mingo@...nel.org>, Andy Lutomirski <luto@...nel.org>,
	X86 ML <x86@...nel.org>, Marcelo Tosatti <mtosatti@...hat.com>,
	Radim Krcmar <rkrcmar@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	kvm list <kvm@...r.kernel.org>, Alexander Graf <agraf@...e.de>
Subject: Re: [PATCH 2/5] x86, vdso, pvclock: Simplify and speed up the vdso
 pvclock reader

On Fri, Dec 11, 2015 at 12:42 AM, Paolo Bonzini <pbonzini@...hat.com> wrote:
>
>
> On 11/12/2015 08:52, Ingo Molnar wrote:
>>
>> * Paolo Bonzini <pbonzini@...hat.com> wrote:

>>>
>>> Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
>>
>> Thanks. I've added your Reviewed-by to the 1/5 patch as well - to be able to put
>> the whole series into the tip:x86/entry tree. Let me know if you'd like it to be
>> done differently.
>
> The 1/5 patch is entirely in KVM and is not necessary for the rest of
> the series to work.  I would like it to be separate, because Marcelo has
> not yet chimed in to say why it was necessary.
>
> Can you just apply patches 2-5?

Yes, please.  I don't grok the clock update mechanism in the KVM host
well enough to be sure that patch 1 is actually correct.  All I know
is that it works better on my laptop with the patch than without the
patch and that it seems at least conceptually correct.

In any event, patch 1 is a host patch and 2-5 are guest patches, and
they only interact to the extent that it's hard for me to test 2-5 on
the guest without patch 1 on the host because without patch 1 my
laptop's host kernel tends to disable stable kvmclock, thus disabling
the entire mechanism in the guest.

--Andy
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