Re: [PATCH v5 7/8] KVM: SVM: Add Page modification logging support

["Huang, Kai" <kai.huang@intel.com>]

On Mon, 2026-01-05 at 06:36 +0000, Nikunj A Dadhania wrote:
> Currently, dirty logging relies on write protecting guest memory and
> marking dirty GFNs during subsequent write faults. This method works but
> incurs overhead due to additional write faults for each dirty GFN.
> 
> Implement support for the Page Modification Logging (PML) feature, a
> hardware-assisted method for efficient dirty logging. PML automatically
> logs dirty GPA[51:12] to a 4K buffer when the CPU sets NPT D-bits. Two new
> VMCB fields are utilized: PML_ADDR and PML_INDEX. The PML_INDEX is
> initialized to 511 (8 bytes per GPA entry), and the CPU decreases the
> PML_INDEX after logging each GPA. When the PML buffer is full, a
> VMEXIT(PML_FULL) with exit code 0x407 is generated.
> 
> 

Could you add sentence(s) to clarify PML works for SEV* guests on hardware
level in the same way as for normal SVM guests?

This justifies the code change like always setting cpu_dirty_log_size for
all AMD VMs when PML is enabled in svm_vm_init() (IIRC).  Otherwise you
need to have code to make sure it's cleared for SEV* guests.