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Fri, 06 Jun 2025 11:48:39 -0700 (PDT) MIME-Version: 1.0 References: <20250127160709.80604-1-ubizjak@gmail.com> <20250127160709.80604-7-ubizjak@gmail.com> <02c00acd-9518-4371-be2c-eb63e5d11d9c@kernel.org> <9767d411-81dc-491b-b6da-419240065ffe@kernel.org> In-Reply-To: From: Uros Bizjak Date: Fri, 6 Jun 2025 20:48:36 +0200 X-Gm-Features: AX0GCFvXERXK_nHAKIR60I6AOdB-3j1GvEhNua1NJKWBq6uXzktIDbaVIardb-k Message-ID: Subject: Re: Large modules with 6.15 [was: [PATCH v4 6/6] percpu/x86: Enable strict percpu checks via named AS qualifiers] To: Alexei Starovoitov Cc: Jiri Slaby , Dave Hansen , X86 ML , linux-mm , LKML , linux-bcachefs@vger.kernel.org, linux-arch , Network Development , Nadav Amit , Dennis Zhou , Tejun Heo , Christoph Lameter , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Linus Torvalds , Andy Lutomirski , Brian Gerst , Peter Zijlstra , Shung-Hsi Yu Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: 6ED68A0003 X-Rspamd-Server: rspam09 X-Stat-Signature: fk45pisqu6jrgbmm4cgdrmo9nmrwno3o X-HE-Tag: 1749235721-474121 X-HE-Meta: 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 Bscb9pIz V7XOd/pvGlyUa8DchW9H0FXybRVNk0/WcmJ/2gUop+ruP83iEc4IMY7+jtg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Jun 6, 2025 at 6:39=E2=80=AFPM Alexei Starovoitov wrote: > > On Fri, Jun 6, 2025 at 2:27=E2=80=AFAM Uros Bizjak wr= ote: > > > > On Fri, Jun 6, 2025 at 11:17=E2=80=AFAM Jiri Slaby wrote: > > > > > > On 05. 06. 25, 19:31, Uros Bizjak wrote: > > > > On Thu, Jun 5, 2025 at 7:15=E2=80=AFPM Dave Hansen wrote: > > > >> > > > >> On 6/5/25 07:27, Jiri Slaby wrote: > > > >>> Reverting this gives me back to normal sizes. > > > >>> > > > >>> Any ideas? > > > >> > > > >> I don't see any reason not to revert it. The benefits weren't exac= tly > > > >> clear from the changelogs or cover letter. Enabling "various compi= ler > > > >> checks" doesn't exactly scream that this is critical to end users = in > > > >> some way. > > > >> > > > >> The only question is if we revert just this last patch or the whol= e series. > > > >> > > > >> Uros, is there an alternative to reverting? > > > > > > > > This functionality can easily be disabled in include/linux/compiler= .h > > > > by not defining USE_TYPEOF_UNQUAL: > > > > > > > > #if CC_HAS_TYPEOF_UNQUAL && !defined(__CHECKER__) > > > > # define USE_TYPEOF_UNQUAL 1 > > > > #endif > > > > > > > > (support for typeof_unqual keyword is required to handle __seg_gs > > > > qualifiers), but ... > > > > > > > > ... the issue is reportedly fixed, please see [1], and ... > > > > > > Confirmed, I need a patched userspace (libbpf). > > > > > > > ... you will disable much sought of feature, just ask tglx (and ple= ase > > > > read his rant at [2]): > > > > > > Given this is the second time I hit a bug with this, perhaps introduc= e > > > an EXPERIMENTAL CONFIG option, so that random users can simply disabl= e > > > it if an issue occurs? Without the need of patching random userspace = and > > > changing random kernel headers? > > > > In both cases, the patch *exposed* a bug in a related utility > > software, it is not that the patch itself is buggy. IMO, waving off > > the issue by disabling the feature you just risk the bug in the > > related software to hit even harder in some not too distant future. > > The typeof_unqual exposed the issue in the way GCC generates dwarf. > The libbpf/pahole is a workaround for incorrect dwarf. > The compiler shouldn't emit two identical dwarf definition for > one underlying type within one compilation unit. In this case > typeof_unqual somehow confused gcc. Can you please file a bugreport in GCC bugzilla, so we can analyze the issu= e? Uros.