From: Paolo Bonzini <pbonzini@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>,
Michael Ellerman <mpe@ellerman.id.au>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
KVM list <kvm@vger.kernel.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [GIT PULL] Second batch of KVM changes for Linux 5.6-rc4 (or rc5)
Date: Mon, 2 Mar 2020 00:04:59 +0100 [thread overview]
Message-ID: <4f115b07-7d94-da4f-edb2-f4d565c4289e@redhat.com> (raw)
In-Reply-To: <CAHk-=wiin_LkqP2Cm5iPc5snUXYqZVoMFawZ-rjhZnawven8SA@mail.gmail.com>
On 01/03/20 22:33, Linus Torvalds wrote:
> On Sun, Mar 1, 2020 at 1:03 PM Paolo Bonzini <pbonzini@redhat.com> wrote:
>>
>> Paolo Bonzini (4):
>> KVM: allow disabling -Werror
>
> Honestly, this is just badly done.
>
> You've basically made it enable -Werror only for very random
> configurations - and apparently the one you test.
> Doing things like COMPILE_TEST disables it, but so does not having
> EXPERT enabled.
Yes, I took this from the i915 Kconfig. It's temporary, in 5.7 I am
planning to get it to just !KASAN, but for 5.6 I wanted to avoid more
breakage so I added the other restrictions. The difference between
x86-64 and i386 is really just the frame size warnings, which Christoph
triggered because of a higher CONFIG_NR_CPUS.
(BTW, perhaps it makes sense for Sparse to have something like __nostack
for structs that contain potentially large arrays).
> I've merged this, but I wonder why you couldn't just do what I
> suggested originally? Seriously, if you script your build tests,
> and don't even look at the results, then you might as well use
>
> make KCFLAGS=-Werror
I did that and I'm also adding W=1; and I threw in a smaller than
default frame size warning option too because I don't want cpumasks on
the stack anyway. However, that wouldn't help contributors. I'm okay
if I get W=1 or frame size warnings from patches from other
contributors, but I think it's a disservice to them that they have to
set KCFLAGS in order to avoid warnings.
> the "now it causes problems for
> random compiler versions" is a real issue again - but at least it
> wouldn't be a random kernel subsystem that happens to trigger it, it
> would be a _generic_ issue, and we'd have everybody involved when a
> compiler change introduces a new warning.
Yes, and GCC prereleases are tested with Linux, for example by doing
full Rawhide rebuilds. If we started using -Werror by default
(including allyesconfig), they would probably report warnings early.
Same for clang.
I hope that Linux can have -Werror everywhere, or at least a
CONFIG_WERROR option that does it even if it defaults to n for a release
or more. But I don't think we can get there without first seeing what
issues pop up in a few subsystems or arches---even before considering
new compilers---so I decided I would just try.
Paolo
> Adding the powerpc people, since they have more history with their
> somewhat less hacky one. Except that one automatically gets disabled
> by "make allmodconfig" and friends, which is also kind of pointless.
> Michael, what tends to be the triggers for people using
> PPC_DISABLE_WERROR? Do you have reports for it? Could we have a
> _generic_ option that just gets enabled by default, except it gets
> disabled by _known_ issues (like KASAN).
>
> Being disabled for "make allmodconfig" is kind of against one of the
> _points_ of "the build should be warning-free".
next prev parent reply other threads:[~2020-03-01 23:05 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-01 19:03 [GIT PULL] Second batch of KVM changes for Linux 5.6-rc4 (or rc5) Paolo Bonzini
2020-03-01 21:33 ` Linus Torvalds
2020-03-01 23:04 ` Paolo Bonzini [this message]
2020-03-02 5:10 ` Nathan Chancellor
2020-03-02 10:51 ` Michael Ellerman
2020-03-02 12:14 ` Segher Boessenkool
2020-03-01 22:45 ` pr-tracker-bot
2020-03-02 5:38 ` Naresh Kamboju
2020-03-02 7:21 ` Wanpeng Li
2020-03-02 11:31 ` Anders Roxell
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