| Message ID | 20191024120938.11237-1-david@redhat.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | mm: Don't mark hotplugged pages PG_reserved (including ZONE_DEVICE) | expand |
On 24.10.19 14:09, David Hildenbrand wrote: > This is the result of a recent discussion with Michal ([1], [2]). Right > now we set all pages PG_reserved when initializing hotplugged memmaps. This > includes ZONE_DEVICE memory. In case of system memory, PG_reserved is > cleared again when onlining the memory, in case of ZONE_DEVICE memory > never. > > In ancient times, we needed PG_reserved, because there was no way to tell > whether the memmap was already properly initialized. We now have > SECTION_IS_ONLINE for that in the case of !ZONE_DEVICE memory. ZONE_DEVICE > memory is already initialized deferred, and there shouldn't be a visible > change in that regard. > > One of the biggest fears were side effects. I went ahead and audited all > users of PageReserved(). The details can be found in "mm/memory_hotplug: > Don't mark pages PG_reserved when initializing the memmap". > > This patch set adapts all relevant users of PageReserved() to keep the > existing behavior in respect to ZONE_DEVICE pages. The biggest part part > that needs changes is KVM, to keep the existing behavior (that's all I > care about in this series). > > Note that this series is able to rely completely on pfn_to_online_page(). > No new is_zone_device_page() calles are introduced (as requested by Dan). > We are currently discussing a way to mark also ZONE_DEVICE memmaps as > active/initialized - pfn_active() - and lightweight locking to make sure > memmaps remain active (e.g., using RCU). We might later be able to convert > some suers of pfn_to_online_page() to pfn_active(). Details can be found > in [3], however, this represents yet another cleanup/fix we'll perform > on top of this cleanup. > > I only gave it a quick test with DIMMs on x86-64, but didn't test the > ZONE_DEVICE part at all (any tips for a nice QEMU setup?). Also, I didn't > test the KVM parts (especially with ZONE_DEVICE pages or no memmap at all). > Compile-tested on x86-64 and PPC. > Jeff Moyer ran some NVDIMM test cases for me (thanks!!!), including xfstests, pmdk, and ndctl. No regressions found. I will run some KVM tests, especially NDIMM passthrough, but will have to setup a test environment first. I would appreciate some review in the meantime. :)
This is the result of a recent discussion with Michal ([1], [2]). Right now we set all pages PG_reserved when initializing hotplugged memmaps. This includes ZONE_DEVICE memory. In case of system memory, PG_reserved is cleared again when onlining the memory, in case of ZONE_DEVICE memory never. In ancient times, we needed PG_reserved, because there was no way to tell whether the memmap was already properly initialized. We now have SECTION_IS_ONLINE for that in the case of !ZONE_DEVICE memory. ZONE_DEVICE memory is already initialized deferred, and there shouldn't be a visible change in that regard. One of the biggest fears were side effects. I went ahead and audited all users of PageReserved(). The details can be found in "mm/memory_hotplug: Don't mark pages PG_reserved when initializing the memmap". This patch set adapts all relevant users of PageReserved() to keep the existing behavior in respect to ZONE_DEVICE pages. The biggest part part that needs changes is KVM, to keep the existing behavior (that's all I care about in this series). Note that this series is able to rely completely on pfn_to_online_page(). No new is_zone_device_page() calles are introduced (as requested by Dan). We are currently discussing a way to mark also ZONE_DEVICE memmaps as active/initialized - pfn_active() - and lightweight locking to make sure memmaps remain active (e.g., using RCU). We might later be able to convert some suers of pfn_to_online_page() to pfn_active(). Details can be found in [3], however, this represents yet another cleanup/fix we'll perform on top of this cleanup. I only gave it a quick test with DIMMs on x86-64, but didn't test the ZONE_DEVICE part at all (any tips for a nice QEMU setup?). Also, I didn't test the KVM parts (especially with ZONE_DEVICE pages or no memmap at all). Compile-tested on x86-64 and PPC. Based on next/master. The current version (kept updated) can be found at: https://github.com/davidhildenbrand/linux.git online_reserved_cleanup RFC -> v1: - Dropped "staging/gasket: Prepare gasket_release_page() for PG_reserved changes" - Dropped "staging: kpc2000: Prepare transfer_complete_cb() for PG_reserved changes" - Converted "mm/usercopy.c: Prepare check_page_span() for PG_reserved changes" to "mm/usercopy.c: Update comment in check_page_span() regarding ZONE_DEVICE" - No new users of is_zone_device_page() are introduced. - Rephrased comments and patch descriptions. [1] https://lkml.org/lkml/2019/10/21/736 [2] https://lkml.org/lkml/2019/10/21/1034 [3] https://www.spinics.net/lists/linux-mm/msg194112.html Cc: Michal Hocko <mhocko@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com Cc: Andrew Morton <akpm@linux-foundation.org> Cc: kvm-ppc@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: kvm@vger.kernel.org Cc: linux-hyperv@vger.kernel.org Cc: devel@driverdev.osuosl.org Cc: xen-devel@lists.xenproject.org Cc: x86@kernel.org Cc: Alexander Duyck <alexander.duyck@gmail.com> David Hildenbrand (10): mm/memory_hotplug: Don't allow to online/offline memory blocks with holes KVM: x86/mmu: Prepare kvm_is_mmio_pfn() for PG_reserved changes KVM: Prepare kvm_is_reserved_pfn() for PG_reserved changes vfio/type1: Prepare is_invalid_reserved_pfn() for PG_reserved changes powerpc/book3s: Prepare kvmppc_book3s_instantiate_page() for PG_reserved changes powerpc/64s: Prepare hash_page_do_lazy_icache() for PG_reserved changes powerpc/mm: Prepare maybe_pte_to_page() for PG_reserved changes x86/mm: Prepare __ioremap_check_ram() for PG_reserved changes mm/memory_hotplug: Don't mark pages PG_reserved when initializing the memmap mm/usercopy.c: Update comment in check_page_span() regarding ZONE_DEVICE arch/powerpc/kvm/book3s_64_mmu_radix.c | 14 +++++---- arch/powerpc/mm/book3s64/hash_utils.c | 10 +++--- arch/powerpc/mm/pgtable.c | 10 +++--- arch/x86/kvm/mmu.c | 29 ++++++++++------- arch/x86/mm/ioremap.c | 13 ++++++-- drivers/hv/hv_balloon.c | 6 ++++ drivers/vfio/vfio_iommu_type1.c | 10 ++++-- drivers/xen/balloon.c | 7 +++++ include/linux/page-flags.h | 8 +---- mm/memory_hotplug.c | 43 +++++++++++++++++++------- mm/page_alloc.c | 11 ------- mm/usercopy.c | 6 ++-- virt/kvm/kvm_main.c | 10 ++++-- 13 files changed, 111 insertions(+), 66 deletions(-)