On Wed, Feb 28, 2018 at 03:25:50PM +0800, Haozhong Zhang wrote: > QEMU writes to vNVDIMM backends in the vNVDIMM label emulation and > live migration. If the backend is on the persistent memory, QEMU needs > to take proper operations to ensure its writes persistent on the > persistent memory. Otherwise, a host power failure may result in the > loss the guest data on the persistent memory. > > This v3 patch series is based on Marcel's patch "mem: add share > parameter to memory-backend-ram" [1] because of the changes in patch 1. > > [1] https://lists.gnu.org/archive/html/qemu-devel/2018-02/msg03858.html > > Previous versions can be found at > v3: https://lists.gnu.org/archive/html/qemu-devel/2018-02/msg04365.html > v2: https://lists.gnu.org/archive/html/qemu-devel/2018-02/msg01579.html > v1: https://lists.gnu.org/archive/html/qemu-devel/2017-12/msg05040.html > > Changes in v4: > * (Patch 2) Fix compilation errors found by patchew. > > Changes in v3: > * (Patch 5) Add a is_pmem flag to ram_handle_compressed() and handle > PMEM writes in it, so we don't need the _common function. > * (Patch 6) Expose qemu_get_buffer_common so we can remove the > unnecessary qemu_get_buffer_to_pmem wrapper. > * (Patch 8) Add a is_pmem flag to xbzrle_decode_buffer() and handle > PMEM writes in it, so we can remove the unnecessary > xbzrle_decode_buffer_{common, to_pmem}. > * Move libpmem stubs to stubs/pmem.c and fix the compilation failures > of test-{xbzrle,vmstate}.c. > > Changes in v2: > * (Patch 1) Use a flags parameter in file ram allocation functions. > * (Patch 2) Add a new option 'pmem' to hostmem-file. > * (Patch 3) Use libpmem to operate on the persistent memory, rather > than re-implementing those operations in QEMU. > * (Patch 5-8) Consider the write persistence in the migration path. > > Haozhong Zhang (8): > [1/8] memory, exec: switch file ram allocation functions to 'flags' > parameters > [2/8] hostmem-file: add the 'pmem' option > [3/8] configure: add libpmem support > [4/8] mem/nvdimm: ensure write persistence to PMEM in label emulation > [5/8] migration/ram: ensure write persistence on loading zero pages to PMEM > [6/8] migration/ram: ensure write persistence on loading normal pages to > PMEM > [7/8] migration/ram: ensure write persistence on loading compressed pages > to PMEM > [8/8] migration/ram: ensure write persistence on loading xbzrle pages to > PMEM > > backends/hostmem-file.c | 27 +++++++++++++++++++- > configure | 35 ++++++++++++++++++++++++++ > docs/nvdimm.txt | 14 +++++++++++ > exec.c | 20 ++++++++++++--- > hw/mem/nvdimm.c | 9 ++++++- > include/exec/memory.h | 12 +++++++-- > include/exec/ram_addr.h | 28 +++++++++++++++++++-- > include/migration/qemu-file-types.h | 2 ++ > include/qemu/pmem.h | 27 ++++++++++++++++++++ > memory.c | 8 +++--- > migration/qemu-file.c | 29 ++++++++++++++-------- > migration/ram.c | 49 > +++++++++++++++++++++++++++---------- > migration/ram.h | 2 +- > migration/rdma.c | 2 +- > migration/xbzrle.c | 8 ++++-- > migration/xbzrle.h | 3 ++- > numa.c | 2 +- > qemu-options.hx | 9 ++++++- > stubs/Makefile.objs | 1 + > stubs/pmem.c | 37 ++++++++++++++++++++++++++++ > tests/Makefile.include | 4 +-- > tests/test-xbzrle.c | 4 +-- > 22 files changed, 285 insertions(+), 47 deletions(-) > create mode 100644 include/qemu/pmem.h > create mode 100644 stubs/pmem.c
A few thoughts: 1. Can you use pmem_is_pmem() to auto-detect the pmem=on|off value? 2. The migration/ram code is invasive. Is it really necessary to persist data each time pages are loaded from a migration stream? It seems simpler to migrate as normal and call pmem_persist() just once after RAM has been migrated but before the migration completes. 3. This is independent of this patch series and can be done later. NVDIMM seems incompatible with post-copy live migration. It would be good to have a postcopy_add_blocker() API so that a nice error message is printed if post-copy live migration is attempted. The code itself seems fine though: Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
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