Branch is here: https://github.com/xzpeter/linux/tree/kvm-dirty-ring Overview ============ This is a continued work from Lei Cao <lei.cao@xxxxxxxxxxx> and Paolo on the KVM dirty ring interface. To make it simple, I'll still start with version 1 as RFC. The new dirty ring interface is another way to collect dirty pages for the virtual machine, but it is different from the existing dirty logging interface in a few ways, majorly: - Data format: The dirty data was in a ring format rather than a bitmap format, so the size of data to sync for dirty logging does not depend on the size of guest memory any more, but speed of dirtying. Also, the dirty ring is per-vcpu (currently plus another per-vm ring, so total ring number is N+1), while the dirty bitmap is per-vm. - Data copy: The sync of dirty pages does not need data copy any more, but instead the ring is shared between the userspace and kernel by page sharings (mmap() on either the vm fd or vcpu fd) - Interface: Instead of using the old KVM_GET_DIRTY_LOG, KVM_CLEAR_DIRTY_LOG interfaces, the new ring uses a new interface called KVM_RESET_DIRTY_RINGS when we want to reset the collected dirty pages to protected mode again (works like KVM_CLEAR_DIRTY_LOG, but ring based) And more. I would appreciate if the reviewers can start with patch "KVM: Implement ring-based dirty memory tracking", especially the document update part for the big picture. Then I'll avoid copying into most of them into cover letter again. I marked this series as RFC because I'm at least uncertain on this change of vcpu_enter_guest(): if (kvm_check_request(KVM_REQ_DIRTY_RING_FULL, vcpu)) { vcpu->run->exit_reason = KVM_EXIT_DIRTY_RING_FULL; /* * If this is requested, it means that we've * marked the dirty bit in the dirty ring BUT * we've not written the date. Do it now. */ r = kvm_emulate_instruction(vcpu, 0); r = r >= 0 ? 0 : r; goto out; } I did a kvm_emulate_instruction() when dirty ring reaches softlimit and want to exit to userspace, however I'm not really sure whether there could have any side effect. I'd appreciate any comment of above, or anything else. Tests =========== I wanted to continue work on the QEMU part, but after I noticed that the interface might still prone to change, I posted this series first. However to make sure it's at least working, I've provided unit tests together with the series. The unit tests should be able to test the series in at least three major paths: (1) ./dirty_log_test -M dirty-ring This tests async ring operations: this should be the major work mode for the dirty ring interface, say, when the kernel is queuing more data, the userspace is collecting too. Ring can hardly reaches full when working like this, because in most cases the collection could be fast. (2) ./dirty_log_test -M dirty-ring -c 1024 This set the ring size to be very small so that ring soft-full always triggers (soft-full is a soft limit of the ring state, when the dirty ring reaches the soft limit it'll do a userspace exit and let the userspace to collect the data). (3) ./dirty_log_test -M dirty-ring-wait-queue This sololy test the extreme case where ring is full. When the ring is completely full, the thread (no matter vcpu or not) will be put onto a per-vm waitqueue, and KVM_RESET_DIRTY_RINGS will wake the threads up (assuming until which the ring will not be full any more). Thanks, Cao, Lei (2): KVM: Add kvm/vcpu argument to mark_dirty_page_in_slot KVM: X86: Implement ring-based dirty memory tracking Paolo Bonzini (1): KVM: Move running VCPU from ARM to common code Peter Xu (12): KVM: Add build-time error check on kvm_run size KVM: Implement ring-based dirty memory tracking KVM: Make dirty ring exclusive to dirty bitmap log KVM: Introduce dirty ring wait queue KVM: selftests: Always clear dirty bitmap after iteration KVM: selftests: Sync uapi/linux/kvm.h to tools/ KVM: selftests: Use a single binary for dirty/clear log test KVM: selftests: Introduce after_vcpu_run hook for dirty log test KVM: selftests: Add dirty ring buffer test KVM: selftests: Let dirty_log_test async for dirty ring test KVM: selftests: Add "-c" parameter to dirty log test KVM: selftests: Test dirty ring waitqueue Documentation/virt/kvm/api.txt | 116 +++++ arch/arm/include/asm/kvm_host.h | 2 - arch/arm64/include/asm/kvm_host.h | 2 - arch/x86/include/asm/kvm_host.h | 5 + arch/x86/include/uapi/asm/kvm.h | 1 + arch/x86/kvm/Makefile | 3 +- arch/x86/kvm/mmu/mmu.c | 6 + arch/x86/kvm/vmx/vmx.c | 7 + arch/x86/kvm/x86.c | 12 + include/linux/kvm_dirty_ring.h | 67 +++ include/linux/kvm_host.h | 37 ++ include/linux/kvm_types.h | 1 + include/uapi/linux/kvm.h | 36 ++ tools/include/uapi/linux/kvm.h | 47 ++ tools/testing/selftests/kvm/Makefile | 2 - .../selftests/kvm/clear_dirty_log_test.c | 2 - tools/testing/selftests/kvm/dirty_log_test.c | 452 ++++++++++++++++-- .../testing/selftests/kvm/include/kvm_util.h | 6 + tools/testing/selftests/kvm/lib/kvm_util.c | 103 ++++ .../selftests/kvm/lib/kvm_util_internal.h | 5 + virt/kvm/arm/arm.c | 29 -- virt/kvm/arm/perf.c | 6 +- virt/kvm/arm/vgic/vgic-mmio.c | 15 +- virt/kvm/dirty_ring.c | 156 ++++++ virt/kvm/kvm_main.c | 315 +++++++++++- 25 files changed, 1329 insertions(+), 104 deletions(-) create mode 100644 include/linux/kvm_dirty_ring.h delete mode 100644 tools/testing/selftests/kvm/clear_dirty_log_test.c create mode 100644 virt/kvm/dirty_ring.c -- 2.21.0
