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Peter Anvin" To: Dave Hansen , Em Sharnoff , linux-kernel@vger.kernel.org, x86@kernel.org, linux-mm@kvack.org CC: Ingo Molnar , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Borislav Petkov , "Edgecombe, Rick P" , Oleg Vasilev , Arthur Petukhovsky , Stefan Radig , Misha Sakhnov Subject: Re: [PATCH v3 1/2] x86/mm: Handle alloc failure in phys_*_init() User-Agent: K-9 Mail for Android In-Reply-To: <22cd0fa8-d14d-4d37-a6a1-5e6827d6182b@intel.com> References: <22cd0fa8-d14d-4d37-a6a1-5e6827d6182b@intel.com> Message-ID: <8DA842BD-929D-4CB2-88D8-405F33C9B559@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 180114000C X-Stat-Signature: 8cpfe8icnodsk1zquqap5ixqc4xbqft3 X-Rspam-User: X-HE-Tag: 1749682613-291625 X-HE-Meta: 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 +N5YK8ts plEMjGStMqrJ6h75RPB4XzfQZnaSx550V9uHDdGMmcpN/MB2YiP/PMljMNTA6HBmjt8BNlG3JveXglAgjxJzJCWQbx8x6U1PB9tX0HdPgmmfMG1WqAkd3O6Is/gS081hnz/W7di7HWZwvrVNASxyXQLxP4fs6+tDc4fGDNhKCnvZz2O0+sEEq6l15gZXH10eUF7PhFFKeAiQEd9pAvmKEaPzpd0tF7Gqp/03eKYb6E82xHqDIByaFGybhRXJgG9Ag20ravvWpgydsAKegidNOByCwZZwP3TiB88Rpryl9QHLiY8WGbIVEBj30WCWR4BxgfFtkAQudj4LCwO7wxK0CSrmE4NI2Xd1FHxOkMLY0b415794= 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 June 10, 2025 7:55:36 AM PDT, Dave Hansen wr= ote: >On 6/10/25 03:16, Em Sharnoff wrote: >> + if (!pmd) >> + return (unsigned long)ERR_PTR(-ENOMEM); > >All of this casting isn't great to look at=2E Just about every line of >code that this patch touches also introduces has a cast=2E > >Could you please find a way to reduce the number of casts? > >> + /* >> + * We might have IS_ERR(paddr_last) if allocation failed, but we sho= uld >> + * still update pud before bailing, so that subsequent retries can p= ick >> + * up on progress (here and in phys_pmd_init) without leaking pmd=2E >> + */ > >Please write everything in imperative voice=2E No "we's", please=2E > >> - for (i =3D 0; i < nr_range; i++) >> + for (i =3D 0; i < nr_range; i++) { >> ret =3D kernel_physical_mapping_init(mr[i]=2Estart, mr[i]=2Eend, >> mr[i]=2Epage_size_mask, >> prot); >> + if (IS_ERR((void *)ret)) >> + return ret; >> + } > >Are there any _actual_ users of 'paddr_last'? I see a lot of setting it >and passing it around, but I _think_ this is the only place it actually >gets used=2E Here, the fact that it's an address doesn't even matter=2E > > Given that ERR_PTR and IS_ERR are basically just casts to and from pointer= s, why have them at all?