Branch is here: https://github.com/xzpeter/linux/tree/kvm-dirty-ring (based on 5.4.0) This is v2 of the dirty ring series, and also the first non-RFC version of it. I didn't put a changelog from v1-rfc because I feel like it would be easier to go into the patchset comparing to read that lengthy and probably helpless changelog. However I do like to do a summary here on what has majorly changed, and also some conclusions on the previous v1 discussions. ====================== * Per-vm ring is dropped For x86 (which is still the major focus for now), we found that kvmgt is probably the only one that still writes to the guest without a vcpu context. It would be a complete pity if we keep the per-vm ring only for kvmgt (who shouldn't write directly to guest via kvm api after all...), so remove it. Work should be ongoing in parallel to refactor kvmgt to not use kvm apis like kvm_write_guest(). However I don't want to break kvmgt before it's fixed. So this series uses an interim way to solve this by fallback no-vcpu-context writes to vcpu0 if there is. So we will keep the interface clean (per-vcpu only), while we don't break the code base. After kvmgt is fixed, we can probably even drop this special fallback and kvm->dirty_ring_lock. * Waitqueue is still kept (for now) We did plan to drop the waitqueue, however again if with kvmgt we still have chance to ful-fill a ring (and I feel like it'll definitely happen if we migrate a kvmgt guest). This series will only trigger the waitqueue mechanism if it's the special case (no-vcpu-context) and actually it naturally avoids another mmu lock deadlock issue I've encountered, which is good. For vcpu context writes, now the series is even more strict that we'll directly fail the KVM_RUN if the dirty ring is soft full, until the userspace collects the dirty rings first. That'll guarantee the ring will never be full. With that, I dropped KVM_REQ_DIRTY_RING_FULL together because then it's not needed. Potentially this could still also be used by ARM when there're code paths that dump the ARM device information to the guests (e.g. KVM_DEV_ARM_ITS_SAVE_TABLES). We'll see. No matter what, even if the code is there, x86 (as long as without kvmgt) should never trigger waitqueue. Although the waitqueue is kept, I dropped the complete waitqueue test, simply because now I can never trigger it without kvmgt... * Why not virtio? There's already some discussion during v1 patchset on whether it's good to use virtio for the data path of delivering dirty pages [1]. I'd confess the only thing that we might consider to use is the vring layout (because virtqueue is tightly bound to devices, while we don't have a device contet here), however it's a pity that even we only use the most low-level vring api it'll be at least iov based which is already an overkill for dirty ring (which is literally an array of addresses). So I just kept things easy. ====================== About the patchset: Patch 1-5: Mostly cleanups Patch 6,7: Prepare for the dirty ring interface Patch 8-10: Dirty ring implementation (majorly patch 8) Patch 11-17: Test cases update Please have a look, thanks. [1] V1 is here: https://lore.kernel.org/kvm/20191129213505.18472-1-peterx@xxxxxxxxxx Paolo Bonzini (1): KVM: Move running VCPU from ARM to common code Peter Xu (16): KVM: Remove kvm_read_guest_atomic() KVM: X86: Change parameter for fast_page_fault tracepoint KVM: X86: Don't track dirty for KVM_SET_[TSS_ADDR|IDENTITY_MAP_ADDR] KVM: Cache as_id in kvm_memory_slot KVM: Add build-time error check on kvm_run size KVM: Pass in kvm pointer into mark_page_dirty_in_slot() KVM: X86: Implement ring-based dirty memory tracking KVM: Make dirty ring exclusive to dirty bitmap log KVM: Don't allocate dirty bitmap if dirty ring is enabled 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 Documentation/virt/kvm/api.txt | 96 ++++ arch/arm/include/asm/kvm_host.h | 2 - arch/arm64/include/asm/kvm_host.h | 2 - arch/x86/include/asm/kvm_host.h | 3 + arch/x86/include/uapi/asm/kvm.h | 1 + arch/x86/kvm/Makefile | 3 +- arch/x86/kvm/mmu.c | 6 + arch/x86/kvm/mmutrace.h | 9 +- arch/x86/kvm/vmx/vmx.c | 25 +- arch/x86/kvm/x86.c | 9 + include/linux/kvm_dirty_ring.h | 57 +++ include/linux/kvm_host.h | 44 +- include/trace/events/kvm.h | 78 ++++ include/uapi/linux/kvm.h | 31 ++ tools/include/uapi/linux/kvm.h | 36 ++ tools/testing/selftests/kvm/Makefile | 2 - .../selftests/kvm/clear_dirty_log_test.c | 2 - tools/testing/selftests/kvm/dirty_log_test.c | 420 ++++++++++++++++-- .../testing/selftests/kvm/include/kvm_util.h | 4 + tools/testing/selftests/kvm/lib/kvm_util.c | 64 +++ .../selftests/kvm/lib/kvm_util_internal.h | 3 + virt/kvm/arm/arch_timer.c | 2 +- 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 | 201 +++++++++ virt/kvm/kvm_main.c | 269 +++++++++-- 27 files changed, 1274 insertions(+), 145 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 -- 2.24.1
