[PATCH v2 0/4] KVM: SVM: Add Page Modification Logging (PML) support

[Nikunj A Dadhania <nikunj@amd.com>]

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.

Patch breakdown:
1. Refactor existing VMX PML code to be shared between VMX and SVM
2. Prepare to share the PML page in VMX and SVM
3. Add AMD SVM PML CPUID
4. Implement SVM PML support using the shared infrastructure

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

Changelog:

v2:
* 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 (4):
  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: 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         |  6 +-
 arch/x86/include/uapi/asm/svm.h    |  2 +
 arch/x86/kernel/cpu/scattered.c    |  1 +
 arch/x86/kvm/svm/sev.c             |  2 +-
 arch/x86/kvm/svm/svm.c             | 99 +++++++++++++++++++++++++++++-
 arch/x86/kvm/svm/svm.h             |  4 ++
 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 +++
 12 files changed, 163 insertions(+), 47 deletions(-)


base-commit: a6ad54137af92535cfe32e19e5f3bc1bb7dbd383
-- 
2.48.1