linux-kernel - Re: linux-next: manual merge of the kvm tree with Linus' and the tip trees

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Date:   Tue, 16 Jan 2018 14:37:32 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Radim Krčmář <rkrcmar@...hat.com>,
        KVM <kvm@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux-Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Tom Lendacky <thomas.lendacky@....com>,
        Brijesh Singh <brijesh.singh@....com>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: linux-next: manual merge of the kvm tree with Linus' and the tip
 trees

On 16/01/2018 01:55, Ingo Molnar wrote:
> 
> * Paolo Bonzini <pbonzini@...hat.com> wrote:
> 
>> On 15/01/2018 19:36, Thomas Gleixner wrote:
>>>> Can KVM folks please stop doing random changes to the cpufeatures code
>>>> without talking to x86 maintainers and Borislav?
>>>>
>>>> This wants to go through TIP or at least reviewed and acked.
>>> In fact it needs to go through TIP. We spent a lot of effort to make the
>>> backporting of all this mess simple and this is just shooting a hole in it.
>>
>> I do understand why you want this to go through TIP, but I'm not sure
>> why a change to Processor Tracing is related to PTI or retpolines.  I'm
>> also not sure why it is a problem for backportability, since we always
>> try to send pull requests after TIP.  Is it because 7*32+15 will be free
>> in 4.16 but not earlier?
> 
> It is because certain central x86 changes (such as changes to processor flags)
> are kept on a v4.14 base to keep the PTI backporting efforts manageable.
> 
> Please revert (or rebase) this change from the KVM tree, and submit it separately, 
> as it should have been done to begin with. Please also follow this process in the 
> future: all x86 changes outside arch/x86/kvm/ need an explicit ack from an x86 
> maintainer.

I've always done it like that until
https://marc.info/?l=kvm&m=149335647027790 got no response for three
months, then I thought you didn't care.

We will drop Intel PT support and delay it to 4.17.  Luwei, since your
patches have issues with incorrect use of the MSR bitmap, this is
probably a good thing anyway (better bisectability).  Please repost your
patches at the end of the merge window, then we will wait for an ack
from Thomas/Ingo/Peter.

(Radim, just tell me if you prefer to leave the git tree surgery to me.
  Rebasing on top of commit 5cb0944c0c66004c0d9006a7f0fba5782ae38f69
should be okay for other arches).

Paolo