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    SubjectRe: [PATCH RFC] virtio-mem: check against memhp_get_pluggable_range() which memory we can hotplug
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    On 1/11/21 6:11 PM, David Hildenbrand wrote:
    > 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@redhat.com>
    > Cc: Jason Wang <jasowang@redhat.com>
    > Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
    > Cc: Michal Hocko <mhocko@kernel.org>
    > Cc: Oscar Salvador <osalvador@suse.de>
    > Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
    > Cc: Andrew Morton <akpm@linux-foundation.org>
    > Cc: catalin.marinas@arm.com
    > Cc: teawater <teawaterz@linux.alibaba.com>
    > Cc: Anshuman Khandual <anshuman.khandual@arm.com>
    > Cc: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>
    > Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
    > Cc: hca@linux.ibm.com
    > Cc: Vasily Gorbik <gor@linux.ibm.com>
    > Cc: Will Deacon <will@kernel.org>
    > Cc: Ard Biesheuvel <ardb@kernel.org>
    > Cc: Mark Rutland <mark.rutland@arm.com>
    > Cc: Heiko Carstens <hca@linux.ibm.com>
    > Cc: Michal Hocko <mhocko@kernel.org>
    > Signed-off-by: David Hildenbrand <david@redhat.com>
    > ---
    >
    > This is an example how virito-mem intends to use an interface like
    > memhp_get_pluggable_range() once around. See:
    >
    > "[PATCH V2 0/3] mm/hotplug: Pre-validate the address range with platform"
    > https://lkml.kernel.org/r/1608218912-28932-1-git-send-email-anshuman.khandual@arm.com
    >
    > @Anshuman, feel free to pick up and carry this patch. I'll retest the final
    > result / new versions of you series.

    Makes sense, will carry this patch in the series.

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