linux-kernel - Re: [PATCH RFC] virtio-mem: check against memhp_get_pluggable

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Date:   Fri, 22 Jan 2021 09:02:51 +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:     Oscar Salvador <osalvador@...e.de>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Will Deacon <will@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Pankaj Gupta <pankaj.gupta.linux@...il.com>,
        Michal Hocko <mhocko@...nel.org>,
        Wei Yang <richard.weiyang@...ux.alibaba.com>,
        teawater <teawaterz@...ux.alibaba.com>,
        Pankaj Gupta <pankaj.gupta@...ud.ionos.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: Re: [PATCH RFC] virtio-mem: check against memhp_get_pluggable_range()
 which memory we can hotplug



On 1/21/21 3:27 PM, David Hildenbrand wrote:
> On 18.01.21 14:21, Anshuman Khandual wrote:
>>
>>
>> On 1/18/21 6:43 PM, Anshuman Khandual wrote:
>>> From: David Hildenbrand <david@...hat.com>
>>>
>>> Right now, we only check against MAX_PHYSMEM_BITS - but turns out there
>>> are more restrictions of which memory we can actually hotplug, especially
>>> om arm64 or s390x once we support them: we might receive something like
>>> -E2BIG or -ERANGE from add_memory_driver_managed(), stopping device
>>> operation.
>>>
>>> So, check right when initializing the device which memory we can add,
>>> warning the user. Try only adding actually pluggable ranges: in the worst
>>> case, no memory provided by our device is pluggable.
>>>
>>> In the usual case, we expect all device memory to be pluggable, and in
>>> corner cases only some memory at the end of the device-managed memory
>>> region to not be pluggable.
>>>
>>> Cc: "Michael S. Tsirkin" <mst@...hat.com>
>>> Cc: Jason Wang <jasowang@...hat.com>
>>> Cc: Pankaj Gupta <pankaj.gupta.linux@...il.com>
>>> Cc: Michal Hocko <mhocko@...nel.org>
>>> Cc: Oscar Salvador <osalvador@...e.de>
>>> Cc: Wei Yang <richard.weiyang@...ux.alibaba.com>
>>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>>> Cc: catalin.marinas@....com
>>> Cc: teawater <teawaterz@...ux.alibaba.com>
>>> Cc: Anshuman Khandual <anshuman.khandual@....com>
>>> Cc: Pankaj Gupta <pankaj.gupta@...ud.ionos.com>
>>> Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>
>>> Cc: hca@...ux.ibm.com
>>> Cc: Vasily Gorbik <gor@...ux.ibm.com>
>>> Cc: Will Deacon <will@...nel.org>
>>> Cc: Ard Biesheuvel <ardb@...nel.org>
>>> Cc: Mark Rutland <mark.rutland@....com>
>>> Cc: Heiko Carstens <hca@...ux.ibm.com>
>>> Cc: Michal Hocko <mhocko@...nel.org>
>>> Signed-off-by: David Hildenbrand <david@...hat.com>
>>> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
>>
>> Hello David,
>>
>> As your original patch was in the RFC state, I have just maintained
>> the same here as well. But once you test this patch along with the
>> new series, please do let me know if this needs to be converted to
>> a normal PATCH instead. Thank you.
> 
> Yes, you can drop the RFC part. I assume you'll send another revision,
> I'll do another test there, thanks!

Sure, will drop the RFC in next version.