linux-kernel - [PATCH V3 0/2] mm/kvm/vfio/ppc64: Migrate compound pages out of CMA region

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Message-Id: <20180918115839.22154-1-aneesh.kumar@linux.ibm.com>
Date:   Tue, 18 Sep 2018 17:28:37 +0530
From:   "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
To:     akpm@...ux-foundation.org, Michal Hocko <mhocko@...nel.org>,
        Alexey Kardashevskiy <aik@...abs.ru>, mpe@...erman.id.au
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
Subject: [PATCH V3 0/2] mm/kvm/vfio/ppc64: Migrate compound pages out of CMA region

ppc64 use CMA area for the allocation of guest page table (hash page table). We won't
be able to start guest if we fail to allocate hash page table. We have observed
hash table allocation failure because we failed to migrate pages out of CMA region
because they were pinned. This happen when we are using VFIO. VFIO on ppc64 pins
the entire guest RAM. If the guest RAM pages get allocated out of CMA region, we
won't be able to migrate those pages. The pages are also pinned for the lifetime of the
guest.

Currently we support migration of non-compound pages. With THP and with the addition of
 hugetlb migration we can end up allocating compound pages from CMA region. This
patch series add support for migrating compound pages. The first path adds the helper
get_user_pages_cma_migrate() which pin the page making sure we migrate them out of
CMA region before incrementing the reference count. 

Aneesh Kumar K.V (2):
  mm: Add get_user_pages_cma_migrate
  powerpc/mm/iommu: Allow migration of cma allocated pages during
    mm_iommu_get

 arch/powerpc/mm/mmu_context_iommu.c | 120 ++++++++-----------------
 include/linux/hugetlb.h             |   2 +
 include/linux/migrate.h             |   3 +
 mm/hugetlb.c                        |   4 +-
 mm/migrate.c                        | 132 ++++++++++++++++++++++++++++
 5 files changed, 174 insertions(+), 87 deletions(-)

-- 
2.17.1