[PATCH v6 0/7] KVM: SVM: Add Page Modification Logging (PML) support

Nikunj A Dadhania
2026-04-07T06:33:24Z

This series implements Page Modification Logging (PML) for guests on AMD
processors, 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:
v6:
* Collect RoBs
* Rebase on latest kvm/master
* Dropped SEV PML selftest (Kai Huang)
* Added guard(svm_vmcb01) helpers to temporarily switch to vmcb01
* Use guard(svm_vmcb01) to ensure vmcb01 is targeted during PML updates when L2
is active, similar to VMX. Dropped patch moving nested CPU dirty logging to
common code; upstream now updates vmcs01 on-demand via temporary VMCS switch
instead of deferring updates.

v5: https://lore.kernel.org/kvm/20260105063622.894410-1-nikunj@amd.com/
* Rebased on latest kvm/next
* Use EXPORT_SYMBOL_FOR_KVM_INTERNAL (Kai Huang)
* Use cpu_dirty_log_size instead of enable_pml for PML checks, with this patch
moving enable_pml to common code is not needed (Kai Huang)
* Added SEV PML self test

Nikunj A Dadhania (7):
KVM: x86: Carve out PML flush routine
KVM: x86: Move PML page to common vcpu arch structure
KVM: VMX: Use cpu_dirty_log_size instead of enable_pml for PML checks
x86/cpufeatures: Add Page modification logging
KVM: SVM: Use BIT_ULL for 64-bit nested_ctl bit definitions
KVM: nSVM: Add helpers to temporarily switch to vmcb01
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 | 125 ++++++++++++++++++++++++++++-
arch/x86/kvm/svm/svm.h | 3 +
arch/x86/kvm/vmx/vmx.c | 50 ++++--------
arch/x86/kvm/vmx/vmx.h | 7 --
arch/x86/kvm/x86.c | 31 +++++++
arch/x86/kvm/x86.h | 8 ++
13 files changed, 206 insertions(+), 51 deletions(-)

base-commit: df83746075778958954aa0460cca55f4b3fc9c02
--
2.48.1