linux-kernel - Re: [RFC PATCH 00/26] Runtime paravirt patching

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Message-ID: <37d755a7-8fc9-8cc8-5627-027a8479b6c7@oracle.com>
Date:   Fri, 10 Apr 2020 02:32:35 -0700
From:   Ankur Arora <ankur.a.arora@...cle.com>
To:     Jürgen Groß <jgross@...e.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     peterz@...radead.org, hpa@...or.com, jpoimboe@...hat.com,
        namit@...are.com, mhiramat@...nel.org, bp@...en8.de,
        vkuznets@...hat.com, pbonzini@...hat.com,
        boris.ostrovsky@...cle.com, mihai.carabas@...cle.com,
        kvm@...r.kernel.org, xen-devel@...ts.xenproject.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [RFC PATCH 00/26] Runtime paravirt patching

On 2020-04-08 5:28 a.m., Jürgen Groß wrote:
> On 08.04.20 07:02, Ankur Arora wrote:
[ snip ]
> 
> Quite a lot of code churn and hacks for a problem which should not
> occur on a well administrated machine.
Yeah, I agree the patch set is pretty large and clearly the NMI or
the stop_machine() are completely out. That said, as I wrote in my
other mail I think the problem is still worth solving.

> Especially the NMI dependencies make me not wanting to Ack this series.
The NMI solution did turn out to be pretty ugly.

I was using it to solve two problems: avoid a deadlock where an NMI handler
could use a lock while the stop_machine() thread is trying to rewrite the
corresponding call-sites. And, needed to ensure that we don't lock
and unlock using mismatched primitives.


Thanks
Ankur

> 
> 
> Juergen