[Feature] Page modification logging

[Yingying Zhao]

PML (Page modification logging) is a VT-x feature that allows VMM software to efficiently monitor the guest-physical pages modified during guest execution. It is expected to enhance live migration speed and any other usages that require monitoring guest-physical pages modified during guest execution.

Upstream status:
KVM: target kernel 4.0
Xen: target 4.6

[XiongZhang (xiong-y-zhang)]

kernel 4.0 implement this feature.
843e433 KVM: VMX: Add PML support in VMX
88178fd KVM: x86: Add new dirty logging kvm_x86_ops for PML
1c91cad KVM: x86: Change parameter of kvm_mmu_slot_remove_write_access
9b51a63 KVM: MMU: Explicitly set D-bit for writable spte.
f4b4b18 KVM: MMU: Add mmu help functions to support PML
3b0f1d0 KVM: Rename kvm_arch_mmu_write_protect_pt_masked to be more generic for
d91ffee Optimize TLB flush in kvm_mmu_slot_remove_write_access.
7e71a59 KVM: x86: flush TLB when D bit is manually changed.

[Leann Ogasawara (leannogasawara)]

It appears that commit 3b0f1d0 is dependent on the following 2 additional commits:

commit e108ff2f8033a417ee3e517d9f8730f665646076
Author: Paolo Bonzini <email address hidden>
Date: Thu Jan 15 15:58:54 2015 -0800

    KVM: x86: switch to kvm_get_dirty_log_protect

commit ba0513b5b8ffbcb0cc89e2f172c0bcb70497ba2e
Author: Mario Smarduch <email address hidden>
Date: Thu Jan 15 15:58:53 2015 -0800

    KVM: Add generic support for dirty page logging

[XiongZhang (xiong-y-zhang)]

The Page Modification white paper has been uploaded and added to the SDM landing page. The live pages can be seen here:
http://www.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html
http://www.intel.com/content/www/us/en/processors/page-modification-logging-vmm-white-paper.html