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[79.242.63.197]) by smtp.gmail.com with ESMTPSA id q17sm7350456wrr.53.2020.12.09.23.04.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 09 Dec 2020 23:04:33 -0800 (PST) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: David Hildenbrand Mime-Version: 1.0 (1.0) Subject: Re: [PATCH 3/3] s390/mm: Define arch_get_mappable_range() Date: Thu, 10 Dec 2020 08:04:32 +0100 Message-Id: References: <20201210065845.GA20691@osiris> Cc: Anshuman Khandual , linux-mm@kvack.org, akpm@linux-foundation.org, david@redhat.com, catalin.marinas@arm.com, linux-arm-kernel@lists.infradead.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Vasily Gorbik , Will Deacon , Ard Biesheuvel , Mark Rutland In-Reply-To: <20201210065845.GA20691@osiris> To: Heiko Carstens X-Mailer: iPhone Mail (18B92) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Am 10.12.2020 um 07:58 schrieb Heiko Carstens : >=20 > =EF=BB=BFOn Thu, Dec 10, 2020 at 09:48:11AM +0530, Anshuman Khandual wrote= : >>>> Alternatively leaving __segment_load() and vmem_add_memory() unchanged >>>> will create three range checks i.e two memhp_range_allowed() and the >>>> existing VMEM_MAX_PHYS check in vmem_add_mapping() on all the hotplug >>>> paths, which is not optimal. >>>=20 >>> Ah, sorry. I didn't follow this discussion too closely. I just thought >>> my point of view would be clear: let's not have two different ways to >>> check for the same thing which must be kept in sync. >>> Therefore I was wondering why this next version is still doing >>> that. Please find a way to solve this. >>=20 >> The following change is after the current series and should work with >> and without memory hotplug enabled. There will be just a single place >> i.e vmem_get_max_addr() to update in case the maximum address changes >> from VMEM_MAX_PHYS to something else later. >=20 > Still not. That's way too much code churn for what you want to achieve. > If the s390 specific patch would look like below you can add >=20 > Acked-by: Heiko Carstens >=20 > But please make sure that the arch_get_mappable_range() prototype in > linux/memory_hotplug.h is always visible and does not depend on > CONFIG_MEMORY_HOTPLUG. I'd like to avoid seeing sparse warnings > because of this. >=20 > Thanks. >=20 > diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c > index 77767850d0d0..e0e78234ae57 100644 > --- a/arch/s390/mm/init.c > +++ b/arch/s390/mm/init.c > @@ -291,6 +291,7 @@ int arch_add_memory(int nid, u64 start, u64 size, > if (WARN_ON_ONCE(params->pgprot.pgprot !=3D PAGE_KERNEL.pgprot)) > return -EINVAL; >=20 > + VM_BUG_ON(!memhp_range_allowed(start, size, 1)); > rc =3D vmem_add_mapping(start, size); > if (rc) > return rc; > diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c > index b239f2ba93b0..ccd55e2f97f9 100644 > --- a/arch/s390/mm/vmem.c > +++ b/arch/s390/mm/vmem.c > @@ -4,6 +4,7 @@ > * Author(s): Heiko Carstens > */ >=20 > +#include > #include > #include > #include > @@ -532,11 +533,23 @@ void vmem_remove_mapping(unsigned long start, unsign= ed long size) > mutex_unlock(&vmem_mutex); > } >=20 > +struct range arch_get_mappable_range(void) > +{ > + struct range range; > + > + range.start =3D 0; > + range.end =3D VMEM_MAX_PHYS; > + return range; > +} > + > int vmem_add_mapping(unsigned long start, unsigned long size) > { > + struct range range; > int ret; >=20 > - if (start + size > VMEM_MAX_PHYS || > + range =3D arch_get_mappable_range(); > + if (start < range.start || > + start + size > range.end || > start + size < start) > return -ERANGE; >=20 >=20 Right, what I had in mind as reply to v1. Not sure if we really need new che= cks in common code. Having a new memhp_get_pluggable_range() would be suffic= ient for my use case (virtio-mem).=