linux-kernel - Re: [PATCH 1/3] KVM: X86: Add "nopvspin" parameter to disable PV spinlocks

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Message-ID: <07f979cc-04b8-6901-b7b0-3e9f06655eb6@oracle.com>
Date:   Thu, 3 Oct 2019 17:51:07 +0800
From:   Zhenzhong Duan <zhenzhong.duan@...cle.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        linux-kernel@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krcmar <rkrcmar@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH 1/3] KVM: X86: Add "nopvspin" parameter to disable PV
 spinlocks


On 2019/10/3 0:47, Sean Christopherson wrote:
> On Tue, Oct 01, 2019 at 05:47:00PM +0800, Zhenzhong Duan wrote:
>> On 2019/10/1 16:39, Vitaly Kuznetsov wrote:
>>> Zhenzhong Duan<zhenzhong.duan@...cle.com>  writes:
>>>
>>>> On 2019/9/30 23:41, Vitaly Kuznetsov wrote:
>>>>> Zhenzhong Duan<zhenzhong.duan@...cle.com>   writes:
>>>>>
>>>>>> There are cases where a guest tries to switch spinlocks to bare metal
>>>>>> behavior (e.g. by setting "xen_nopvspin" on XEN platform and
>>>>>> "hv_nopvspin" on HYPER_V).
>>>>>>
>>>>>> That feature is missed on KVM, add a new parameter "nopvspin" to disable
>>>>>> PV spinlocks for KVM guest.
>>>>>>
>>>>>> This new parameter is also intended to replace "xen_nopvspin" and
>>>>>> "hv_nopvspin" in the future.
>>>>> Any reason to not do it right now? We will probably need to have compat
>>>>> code to support xen_nopvspin/hv_nopvspin too but emit a 'is deprecated'
>>>>> warning.
>>>> Sorry the description isn't clear, I'll fix it.
>>>>
>>>> I did the compat work in the other two patches.
>>>> [PATCH 2/3] xen: Mark "xen_nopvspin" parameter obsolete and map it to "nopvspin"
>>>> [PATCH 3/3] x86/hyperv: Mark "hv_nopvspin" parameter obsolete and map it to "nopvspin"
>>>>
>>> For some reason I got CCed only on the first one and moreover,
>> The three patches have different maintainers/reviewers by get_maintainer.pl, I added
>> "Cc: maintainers/reviewers" to each patch then git-sendemail picked them automaticly.
>> I meaned to not disturb maintainers with the field they aren't in charge of. It looks
>> I'm wrong.
>>
>> So what's the correct way dealing with this? Should I send the whole patchset to all
>> the maintainers/reviewers related to all the patches?
> There's no one right answer to that question, folks have different
> preferences.  My general rule of thumb is to cc everyone on all patches
> unless the series is obnoxiously large *and* isolated to a specific part
> of the kernel.  The idea being that people are more likely to be annoyed
> if they can't find all patches in a relatively small series (this case)
> than they are about receiving a mail or two that they don't care about.
>
> At a minimum I would cc everyone involved on the cover letter, and cc the
> relevant mailing lists on all patches.  Sending everyone the cover letter
> provides people a quick overview of the patches they didn't receive, as
> well as a starting point if they want to find those patches.  Cc'ing the
> mailing list(s) can make it even easier to find the patches.  The cover
> letter is also a good place to explain why you didn't cc everyone on all
> patches (or vice versa).
>
> Also, the cover letter should have the shortlog and overall diffstats.
> 'git format-patch --cover-letter' will do the work for you.

Thanks for your detailed reply, I's clear to me what to do now.

Zhenzhong