[PATCH 3/3] s390/mm: Define arch_get_mappable_range()
anshuman.khandual at arm.com
Thu Dec 10 02:40:03 EST 2020
On 12/10/20 12:34 PM, David Hildenbrand wrote:
>> Am 10.12.2020 um 07:58 schrieb Heiko Carstens <hca at linux.ibm.com>:
>> On 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.
>>>> 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.
>>> 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.
>> 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
>> Acked-by: Heiko Carstens <hca at linux.ibm.com>
>> 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.
>> 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 != PAGE_KERNEL.pgprot))
>> return -EINVAL;
>> + VM_BUG_ON(!memhp_range_allowed(start, size, 1));
>> rc = 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 <heiko.carstens at de.ibm.com>
>> +#include <linux/memory_hotplug.h>
>> #include <linux/memblock.h>
>> #include <linux/pfn.h>
>> #include <linux/mm.h>
>> @@ -532,11 +533,23 @@ void vmem_remove_mapping(unsigned long start, unsigned long size)
>> +struct range arch_get_mappable_range(void)
>> + struct range range;
>> + range.start = 0;
>> + range.end = 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 = 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 new checks in common code. Having a new memhp_get_pluggable_range() would be sufficient for my use case (virtio-mem).
Didn't quite understand "Not sure if we really need new checks in common code".
Could you please be more specific. New checks as in pagemap_range() ? Because
other places it is either replacing erstwhile check_hotplug_memory_addressable()
or just moving existing checks from platform arch_add_memory() to the beginning
of various hotplug paths.
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