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Thu, 17 Dec 2020 12:18:54 +0000 (UTC) Received: from [10.36.113.93] (ovpn-113-93.ams2.redhat.com [10.36.113.93]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9E8F060C15; Thu, 17 Dec 2020 12:18:51 +0000 (UTC) Subject: Re: [PATCH 3/3] s390/mm: Define arch_get_mappable_range() To: Anshuman Khandual , Heiko Carstens Cc: linux-mm@kvack.org, akpm@linux-foundation.org, 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 References: <20201210065845.GA20691@osiris> <401e72a7-7865-455a-4c7f-79278e3f0af0@arm.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <62e44a97-0402-2a2b-5364-9b2744814011@redhat.com> Date: Thu, 17 Dec 2020 13:18:50 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <401e72a7-7865-455a-4c7f-79278e3f0af0@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Content-Transfer-Encoding: quoted-printable 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: On 17.12.20 12:45, Anshuman Khandual wrote: >=20 >=20 > On 12/10/20 12:34 PM, David Hildenbrand wrote: >> >>> Am 10.12.2020 um 07:58 schrieb Heiko Carstens : >>> >>> =EF=BB=BFOn Thu, Dec 10, 2020 at 09:48:11AM +0530, Anshuman Khandual = wrote: >>>>>> Alternatively leaving __segment_load() and vmem_add_memory() uncha= nged >>>>>> will create three range checks i.e two memhp_range_allowed() and t= he >>>>>> existing VMEM_MAX_PHYS check in vmem_add_mapping() on all the hotp= lug >>>>>> paths, which is not optimal. >>>>> >>>>> Ah, sorry. I didn't follow this discussion too closely. I just thou= ght >>>>> 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. >>>> >>>> The following change is after the current series and should work wit= h >>>> and without memory hotplug enabled. There will be just a single plac= e >>>> i.e vmem_get_max_addr() to update in case the maximum address change= s >>>> from VMEM_MAX_PHYS to something else later. >>> >>> Still not. That's way too much code churn for what you want to achiev= e. >>> If the s390 specific patch would look like below you can add >>> >>> Acked-by: Heiko Carstens >>> >>> 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. >>> >>> Thanks. >>> >>> 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; >>> >>> + 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 >>> */ >>> >>> +#include >>> #include >>> #include >>> #include >>> @@ -532,11 +533,23 @@ void vmem_remove_mapping(unsigned long start, u= nsigned long size) >>> mutex_unlock(&vmem_mutex); >>> } >>> >>> +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; >>> >>> - 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; >>> >>> >> >> Right, what I had in mind as reply to v1. Not sure if we really need n= ew checks in common code. Having a new memhp_get_pluggable_range() would = be sufficient for my use case (virtio-mem). >=20 > Hello David, >=20 > Quick question. Currently memhp_get_pluggable_range() is a mm/memory_ho= tplug.c > internal static inline function. Only memhp_range_allowed() is availabl= e via > the header include/linux/memory_hotplug.h But For memhp_get_pluggable_r= ange() > to be visible to the drivers, it needs to get included in the header an= d also > be exported via EXPORT_SYMBOL_GPL() in mm/memory_hotplug.c OR just move= the > entire definition as static inline into the header itself. Wondering wh= ich way > would be better ? As it's most likely not on any hot path, exporting the symbol might be the cleanest approach. >=20 > - Anshuman >=20 --=20 Thanks, David / dhildenb