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[209.85.128.175]) by smtp.gmail.com with ESMTPSA id 00721157ae682-6e20d2a4beasm5196097b3.133.2024.09.25.00.13.18 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 25 Sep 2024 00:13:18 -0700 (PDT) Received: by mail-yw1-f175.google.com with SMTP id 00721157ae682-6db4b602e38so51749087b3.1 for ; Wed, 25 Sep 2024 00:13:18 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCXYywqAKwyAZawQljFScAI7mIRgQNG73+9kR23nj6RydHAPyppjdbTA0B5nk4CHG3gUsMLxoEBSiw==@kvack.org X-Received: by 2002:a05:690c:112:b0:6e2:5a8:3447 with SMTP id 00721157ae682-6e21d86342dmr15183337b3.26.1727248398167; Wed, 25 Sep 2024 00:13:18 -0700 (PDT) MIME-Version: 1.0 References: <20240924154205.1491376-1-linux@roeck-us.net> In-Reply-To: <20240924154205.1491376-1-linux@roeck-us.net> From: Geert Uytterhoeven Date: Wed, 25 Sep 2024 09:13:06 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3] mm: Make SPLIT_PTE_PTLOCKS depend on SMP To: Guenter Roeck Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Hildenbrand Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: 1wgzzi7gckzhwcrd6gbmurpkxcgt5esx X-Rspamd-Queue-Id: E4146A0003 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1727248400-168005 X-HE-Meta: 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 /F33HVMi 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 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 Tue, Sep 24, 2024 at 5:42=E2=80=AFPM Guenter Roeck = wrote: > SPLIT_PTE_PTLOCKS depends on "NR_CPUS >=3D 4". Unfortunately, that evalua= tes > to true if there is no NR_CPUS configuration option. This results in > CONFIG_SPLIT_PTE_PTLOCKS=3Dy for mac_defconfig. This in turn causes the m= 68k > "q800" and "virt" machines to crash in qemu if debugging options are > enabled. > > Making CONFIG_SPLIT_PTE_PTLOCKS dependent on the existence of NR_CPUS > does not work since a dependency on the existence of a numeric Kconfig > entry always evaluates to false. Example: > > config HAVE_NO_NR_CPUS > def_bool y > depends on !NR_CPUS > > After adding this to a Kconfig file, "make defconfig" includes: > $ grep NR_CPUS .config > CONFIG_NR_CPUS=3D64 > CONFIG_HAVE_NO_NR_CPUS=3Dy > > Defining NR_CPUS for m68k does not help either since many architectures > define NR_CPUS only for SMP configurations. > > Make SPLIT_PTE_PTLOCKS depend on SMP instead to solve the problem. > > Fixes: 394290cba966 ("mm: turn USE_SPLIT_PTE_PTLOCKS / USE_SPLIT_PTE_PTLO= CKS into Kconfig options") > Cc: David Hildenbrand > Cc: Andrew Morton > Cc: Geert Uytterhoeven > Signed-off-by: Guenter Roeck Reviewed-by: Geert Uytterhoeven Tested-by: Geert Uytterhoeven > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -595,6 +595,7 @@ config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE > config SPLIT_PTE_PTLOCKS > def_bool y > depends on MMU > + depends on SMP > depends on NR_CPUS >=3D 4 Nit: please combine these two lines, to make it clear they are related. > depends on !ARM || CPU_CACHE_VIPT > depends on !PARISC || PA20 Gr{oetje,eeting}s, Geert --=20 Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k= .org In personal conversations with technical people, I call myself a hacker. Bu= t when I'm talking to journalists I just say "programmer" or something like t= hat. -- Linus Torvalds