linux-kernel - Re: [PATCH v13 00/12] KVM: guest_memfd: Add NUMA mempolicy support

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Message-ID: <aPJzjWzL4EbwDM66@google.com>
Date: Fri, 17 Oct 2025 09:49:17 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
Cc: Ackerley Tng <ackerleytng@...gle.com>, Miguel Ojeda <ojeda@...nel.org>, 
	Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
	Paolo Bonzini <pbonzini@...hat.com>, linux-arm-kernel@...ts.infradead.org, 
	kvmarm@...ts.linux.dev, kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Shivank Garg <shivankg@....com>, David Hildenbrand <david@...hat.com>, Fuad Tabba <tabba@...gle.com>, 
	Ashish Kalra <ashish.kalra@....com>, Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH v13 00/12] KVM: guest_memfd: Add NUMA mempolicy support

On Fri, Oct 17, 2025, Miguel Ojeda wrote:
> On Fri, Oct 17, 2025 at 1:57 AM Ackerley Tng <ackerleytng@...gle.com> wrote:
> >
> > Using the command on virt/ would pick it up. Would it be better to add
> > "virt/" to the "automation" + update .clang-format while we're at it?
> 
> Yeah, that is what I was suggesting if you rely on it (and if the
> maintainers of the relevant folders are OK with it).

Hmm, my vote would be to go all-or-nothing for KVM (x86), i.e. include everything
in KVM, or explicitly filter out KVM.  I don't see how auto-formatting can be
useful if it's wildly inconsistent, e.g. if it works for some KVM for-each macros,
but clobbers others.

And I'm leaning towards filtering out KVM, because I'm not sure I want to encourage
use of auto-formatting.  I can definitely see how it's useful, but so much of the
auto-formatting is just _awful_.

E.g. I ran it on a few KVM files and it generated changes like this

-       intel_pmu_enable_fixed_counter_bits(pmu, INTEL_FIXED_0_KERNEL |
-                                                INTEL_FIXED_0_USER |
-                                                INTEL_FIXED_0_ENABLE_PMI);
+       intel_pmu_enable_fixed_counter_bits(
+               pmu, INTEL_FIXED_0_KERNEL | INTEL_FIXED_0_USER |
+                            INTEL_FIXED_0_ENABLE_PMI);

and 

-                       intel_pmu_enable_fixed_counter_bits(pmu, ICL_FIXED_0_ADAPTIVE);
+                       intel_pmu_enable_fixed_counter_bits(
+                               pmu, ICL_FIXED_0_ADAPTIVE);

There are definitely plenty of good changes as well, but overall I find the results
to be very net negative.  That's obviously highly subjective, and maybe there's
settings in clangd I can tweak to make things more to my liking, but my initial
reaction is that I don't want to actively encourage use of auto-formatting in KVM.

I think no matter what, any decision should be in a separate, dedicated patch/thread.
So for this series, I'll drop the .clang-format change when applying, assuming
nothing else pops that requires a new version.