From: Anshuman Khandual <anshuman.khandual@arm.com>
To: Heiko Carstens <hca@linux.ibm.com>
Cc: linux-mm@kvack.org, akpm@linux-foundation.org, david@redhat.com,
linux-arm-kernel@lists.infradead.org, linux-s390@vger.kernel.org,
linux-kernel@vger.kernel.org, Vasily Gorbik <gor@linux.ibm.com>
Subject: Re: [RFC V2 3/3] s390/mm: Define arch_get_mappable_range()
Date: Thu, 3 Dec 2020 06:03:00 +0530 [thread overview]
Message-ID: <24905c32-f6c1-97a0-000f-f822b9870ea5@arm.com> (raw)
In-Reply-To: <20201202203233.GB11274@osiris>
On 12/3/20 2:02 AM, Heiko Carstens wrote:
> On Mon, Nov 30, 2020 at 08:59:52AM +0530, Anshuman Khandual wrote:
>> This overrides arch_get_mappabble_range() on s390 platform and drops now
>> redundant similar check in vmem_add_mapping(). This compensates by adding
>> a new check __segment_load() to preserve the existing functionality.
>>
>> Cc: Heiko Carstens <hca@linux.ibm.com>
>> Cc: Vasily Gorbik <gor@linux.ibm.com>
>> Cc: David Hildenbrand <david@redhat.com>
>> Cc: linux-s390@vger.kernel.org
>> Cc: linux-kernel@vger.kernel.org
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
>> ---
>> arch/s390/mm/extmem.c | 5 +++++
>> arch/s390/mm/vmem.c | 13 +++++++++----
>> 2 files changed, 14 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/s390/mm/extmem.c b/arch/s390/mm/extmem.c
>> index 5060956b8e7d..cc055a78f7b6 100644
>> --- a/arch/s390/mm/extmem.c
>> +++ b/arch/s390/mm/extmem.c
>> @@ -337,6 +337,11 @@ __segment_load (char *name, int do_nonshared, unsigned long *addr, unsigned long
>> goto out_free_resource;
>> }
>>
>> + if (seg->end + 1 > VMEM_MAX_PHYS || seg->end + 1 < seg->start_addr) {
>> + rc = -ERANGE;
>> + goto out_resource;
>> + }
>> +
>> rc = vmem_add_mapping(seg->start_addr, seg->end - seg->start_addr + 1);
>> if (rc)
>> goto out_resource;
>> diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
>> index b239f2ba93b0..06dddcc0ce06 100644
>> --- a/arch/s390/mm/vmem.c
>> +++ b/arch/s390/mm/vmem.c
>> @@ -532,14 +532,19 @@ 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;
>> + return memhp_range;
>> +}
>> +
>> int vmem_add_mapping(unsigned long start, unsigned long size)
>> {
>> int ret;
>>
>> - if (start + size > VMEM_MAX_PHYS ||
>> - start + size < start)
>> - return -ERANGE;
>> -
>
> I really fail to see how this could be considered an improvement for
> s390. Especially I do not like that the (central) range check is now
> moved to the caller (__segment_load). Which would mean potential
> additional future callers would have to duplicate that code as well.
The physical range check is being moved to the generic hotplug code
via arch_get_mappable_range() instead, making the existing check in
vmem_add_mapping() redundant. Dropping the check there necessitates
adding back a similar check in __segment_load(). Otherwise there
will be a loss of functionality in terms of range check.
May be we could just keep this existing check in vmem_add_mapping()
as well in order avoid this movement but then it would be redundant
check in every hotplug path.
So I guess the choice is to either have redundant range checks in
all hotplug paths or future internal callers of vmem_add_mapping()
take care of the range check.
next prev parent reply other threads:[~2020-12-03 0:34 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-30 3:29 [RFC V2 0/3] mm/hotplug: Pre-validate the address range with platform Anshuman Khandual
2020-11-30 3:29 ` [RFC V2 1/3] mm/hotplug: Prevalidate the address range being added " Anshuman Khandual
2020-12-02 9:20 ` David Hildenbrand
2020-12-02 12:15 ` Anshuman Khandual
2020-11-30 3:29 ` [RFC V2 2/3] arm64/mm: Define arch_get_mappable_range() Anshuman Khandual
2020-12-02 9:26 ` David Hildenbrand
2020-12-02 12:17 ` Anshuman Khandual
2020-11-30 3:29 ` [RFC V2 3/3] s390/mm: " Anshuman Khandual
2020-12-02 20:32 ` Heiko Carstens
2020-12-03 0:33 ` Anshuman Khandual [this message]
2020-12-03 11:51 ` Heiko Carstens
2020-12-03 12:01 ` David Hildenbrand
2020-12-07 4:38 ` Anshuman Khandual
2020-12-07 9:03 ` David Hildenbrand
2020-12-08 5:32 ` Anshuman Khandual
2020-12-08 8:38 ` David Hildenbrand
2020-12-02 6:44 ` [RFC V2 0/3] mm/hotplug: Pre-validate the address range with platform Anshuman Khandual
2020-12-02 20:35 ` Heiko Carstens
2020-12-03 0:12 ` Anshuman Khandual
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