linux-kernel - Re: [PATCH V2 3/3] s390/mm: Define arch_get_mappable

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Date:   Wed, 13 Jan 2021 12:32:34 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
        akpm@...ux-foundation.org, hca@...ux.ibm.com,
        catalin.marinas@....com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, Vasily Gorbik <gor@...ux.ibm.com>,
        Will Deacon <will@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH V2 3/3] s390/mm: Define arch_get_mappable_range()



On 1/11/21 4:10 PM, David Hildenbrand wrote:
> On 17.12.20 16:28, Anshuman Khandual wrote:
>> This overrides arch_get_mappabble_range() on s390 platform which will be
>> used with recently added generic framework. It modifies the existing range
>> check in vmem_add_mapping() using arch_get_mappable_range(). It also adds a
>> VM_BUG_ON() check that would ensure that memhp_range_allowed() has already
>> been called on the hotplug path.
>>
>> Cc: Heiko Carstens <hca@...ux.ibm.com>
>> Cc: Vasily Gorbik <gor@...ux.ibm.com>
>> Cc: David Hildenbrand <david@...hat.com>
>> Cc: linux-s390@...r.kernel.org
>> Cc: linux-kernel@...r.kernel.org
>> Acked-by: Heiko Carstens <hca@...ux.ibm.com>
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
>> ---
>>  arch/s390/mm/init.c |  1 +
>>  arch/s390/mm/vmem.c | 15 ++++++++++++++-
>>  2 files changed, 15 insertions(+), 1 deletion(-)
>>
>> 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));
> 
> s/1/true/

Sure, will do.

> 
>>  	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..e10e563ad2b4 100644
>> --- a/arch/s390/mm/vmem.c
>> +++ b/arch/s390/mm/vmem.c
>> @@ -4,6 +4,7 @@
>>   *    Author(s): Heiko Carstens <heiko.carstens@...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)
>>  	mutex_unlock(&vmem_mutex);
>>  }
>>  
>> +struct range arch_get_mappable_range(void)
>> +{
>> +	struct range memhp_range;
>> +
>> +	memhp_range.start = 0;
>> +	memhp_range.end =  VMEM_MAX_PHYS;
> 
> s/  / /
> 
> IIRC, the range is inclusive? "VMEM_MAX_PHYS - 1" then, and adjust the
> check below.

Right, the memory range is inclusive at both ends. Hence will update the
code here.

diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
index 21cabe3473d7..afc39ff1cc8d 100644
--- a/arch/s390/mm/vmem.c
+++ b/arch/s390/mm/vmem.c
@@ -538,7 +538,7 @@ struct range arch_get_mappable_range(void)
        struct range memhp_range;
 
        memhp_range.start = 0;
-       memhp_range.end =  VMEM_MAX_PHYS;
+       memhp_range.end =  VMEM_MAX_PHYS - 1;
        return memhp_range;
 }
 
@@ -549,7 +549,7 @@ int vmem_add_mapping(unsigned long start, unsigned long size)
 
        range = arch_get_mappable_range();
        if (start < range.start ||
-           start + size > range.end ||
+           start + size > range.end + 1 ||
            start + size < start)
                return -ERANGE;

(start + size - 1) is valid only when it is upto the inclusive range.end value.