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Mon, 12 Jan 2026 04:23:42 +0000 Received: from smtpav05.wdc07v.mail.ibm.com (smtpav05.wdc07v.mail.ibm.com [10.39.53.232]) by smtprelay02.wdc07v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 60C4NfNt18612842 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 12 Jan 2026 04:23:41 GMT Received: from smtpav05.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BF6C45805D; Mon, 12 Jan 2026 04:23:41 +0000 (GMT) Received: from smtpav05.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 553FD58043; Mon, 12 Jan 2026 04:23:40 +0000 (GMT) Received: from jarvis.ozlabs.ibm.com (unknown [9.150.20.59]) by smtpav05.wdc07v.mail.ibm.com (Postfix) with ESMTP; Mon, 12 Jan 2026 04:23:39 +0000 (GMT) Message-ID: <15b33dda3ccf6889dbd46b0a0f4edfe633b968f5.camel@linux.ibm.com> Subject: Re: [PATCH] powerpc/mm: Use pte_advance_pfn() in set_huge_pte_at() From: Andrew Donnellan To: "Christophe Leroy (CS GROUP)" , linuxppc-dev@lists.ozlabs.org Date: Mon, 12 Jan 2026 15:23:38 +1100 In-Reply-To: <2462a770-7da3-4b42-99ed-6ffd4d44b4f4@kernel.org> References: <20251219-set_huge_pte_at_pte_advance_pfn-v1-1-e3378845af7d@linux.ibm.com> <2462a770-7da3-4b42-99ed-6ffd4d44b4f4@kernel.org> Content-Type: text/plain; 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i < sz / pdsize; i++, ptep++, addr +=3D pdsi= ze) { > > =C2=A0=C2=A0 __set_pte_at(mm, addr, ptep, pte, 0); > > - pte =3D __pte(pte_val(pte) + ((unsigned long long)pdsize / > > PAGE_SIZE << PFN_PTE_SHIFT)); > > + pte =3D pte_advance_pfn(pte, pdsize / PAGE_SIZE); >=20 > How can this work ? >=20 > pdsize is 4M, PAGE_SIZE is 4k so pdsize/PAGE_SIZE is 0x400. >=20 > PFN_PTE_SHIFT is 24. >=20 > 0x400 << 24 is more than what an unsigned long can contain in=20 > pte_advance_pfn() Ah, in spite of the explicit unsigned long long cast that should've reminde= d me otherwise, I forgot that a long isn't 64 bits on 32 bit machines. >=20 --=20 Andrew Donnellan OzLabs, ADL Canberra ajd@linux.ibm.com IBM Australia Limited