[PATCH v3 0/5] KVM: SVM: Add Page Modification Logging (PML) support

Nikunj A Dadhania
2025-09-25T10:11:17Z

This series implements Page Modification Logging (PML) for guests, bringing
hardware-assisted dirty logging support. PML is designed to track guest
modified memory pages. PML enables the hypervisor to identify which pages in a
guest's memory have been modified since the last checkpoint or during live
migration.

The PML feature uses two new VMCB fields (PML_ADDR and PML_INDEX) and
generates a VMEXIT when the 4KB log buffer becomes full.

The feature is enabled by default when hardware support is detected and
can be disabled via the 'pml' module parameter.

Changelog:
v3:
* Update comments with nested details (Kai Huang)
* Added nested.update_vmcb01_cpu_dirty_logging to update L1 PML (Kai Huang)
* Added patch to use BIT_ULL() instead of BIT() for 64-bit nested_ctl

v2: https://lore.kernel.org/kvm/20250915085938.639049-1-nikunj@amd.com/
* Rebased on latest kvm/next
* Added patch to move pml_pg field from struct vcpu_vmx to struct kvm_vcpu_arch
to share the PML page. (Kai Huang)
* Dropped the SNP safe allocation optimization patch, will submit it separately.
* Update commit message adding explicit mention that AMD PML follows VMX behavior
(Kai Huang)
* Updated SNP erratum comment to include PML buffer alongside VMCB, VMSA, and
AVIC pages. (Kai Huang)

RFC: https://lore.kernel.org/kvm/20250825152009.3512-1-nikunj@amd.com/

Nikunj A Dadhania (5):
KVM: x86: Carve out PML flush routine
KVM: x86: Move PML page to common vcpu arch structure
x86/cpufeatures: Add Page modification logging
KVM: SVM: Use BIT_ULL for 64-bit nested_ctl bit definitions
KVM: SVM: Add Page modification logging support

arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/include/asm/kvm_host.h | 2 +
arch/x86/include/asm/svm.h | 12 ++--
arch/x86/include/uapi/asm/svm.h | 2 +
arch/x86/kernel/cpu/scattered.c | 1 +
arch/x86/kvm/svm/nested.c | 13 +++-
arch/x86/kvm/svm/sev.c | 2 +-
arch/x86/kvm/svm/svm.c | 100 ++++++++++++++++++++++++++++-
arch/x86/kvm/svm/svm.h | 5 ++
arch/x86/kvm/vmx/vmx.c | 48 ++++----------
arch/x86/kvm/vmx/vmx.h | 7 --
arch/x86/kvm/x86.c | 31 +++++++++
arch/x86/kvm/x86.h | 7 ++
13 files changed, 179 insertions(+), 52 deletions(-)

base-commit: a6ad54137af92535cfe32e19e5f3bc1bb7dbd383
--
2.48.1