* Christian Pinto (c.pi...@virtualopensystems.com) wrote: > This patch series introduces a set of fixes to the previous work proposed by > Hailiang Zhang to enable in QEMU live memory snapshot based > on userfaultfd. See discussion here: > http://www.mail-archive.com/qemu-devel@nongnu.org/msg393118.html
Thanks for posting this, > These patches apply on top of: > https://github.com/coloft/qemu/tree/snapshot-v2 > that is the latest version of Hailiang's work, and rely on the latest work on > userfaultfd available on Andrea Arcangeli's Linux kernel tree: > https://git.kernel.org/cgit/linux/kernel/git/andrea/aa.git/log/?h=userfault > > The original work was mainly tested on x86 tcg machines and was not working > ARM/ARM64 tcg. > The fixes presented in this series enable the live memory snapshot > to work for ARM64 tcg guests running on top of an ARM64 host. > > The main problems encountered were: > - QEMU uses for ARM a memory page size of 1KB. Even though this size is > not > supported by the Linux kernel, is is kept for backward compatibility > with older ARM CPU MMUs. Initial work was write-unprotecting pages with > a granularity not always aligned with host page size, causing > userfaultfd > to fail. Yes, Power similarly has a 4kb size for the target page size even though the host kernel is normally a large page size. > - The VM execution was resumed right before the status of the migration > was switched from MIGRATION_STATUS_SETUP to MIGRATION_STATUS_ACTIVE. > This was causing again the VM to trigger a "Bus error", due to wrong > status of some memory pages. > - When unprotecting a memory page the flag > UFFDIO_WRITEPROTECT_MODE_DONTWAKE was used. This way, after a page is > copied into snapshot file, the virtual machine execution is not resumed. > > > To test the patches on an ARM64 host, boot an ARM64 tcg machine: > > qemu-system-aarch64 -machine virt,accel=tcg -cpu cortex-a57\ > -m 256 -kernel Image \ > -initrd rootfs.cpio.gz \ > -append "earlyprintk rw console=ttyAMA0" \ > -net nic -net user \ > -nographic -serial pty -monitor stdio > > start migration from QEMU monitor: > > (qemu) migrate file:/root/test_snapshot > > > resume VM form snapshot: > > qemu-system-aarch64 -machine virt,accel=tcg -cpu cortex-a57\ > -m 256 -kernel Image \ > -initrd rootfs.cpio.gz \ > -append "earlyprintk rw console=ttyAMA0" \ > -net nic -net user \ > -nographic -serial stdio -monitor pty \ > -incoming file:/root/test_snapshot Nice, what's your use case and how are you dealing with storage? Dave > Christian Pinto (4): > migration/postcopy-ram: check pagefault flags in userfaultfd thread > migration/ram: Fix for ARM/ARM64 page size > migration: snapshot thread > migration/postcopy-ram: ram_set_pages_wp fix > > migration/migration.c | 9 +++++---- > migration/postcopy-ram.c | 25 ++++++++----------------- > migration/ram.c | 18 ++++++++++++++---- > 3 files changed, 27 insertions(+), 25 deletions(-) > > -- > 2.11.0 > -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
