Re: [PATCH] db/leaf_8000000a: Add Page modification logging

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

On 8/15/2025 12:45 PM, Ahmed S. Darwish wrote:
> Hi,
> 
> On Mon, 11 Aug 2025, Nikunj A Dadhania wrote:
>>
>> Page modification logging(PML) is hardware feature designed to track
>> guest modified memory pages. PML enables the hypervisor to identify
>> which pages in a guest's memory have been changed since the last
>> checkpoint or during live migration.
>>
>> Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
>> ---
>>  db/xml/leaf_8000000a.xml | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/db/xml/leaf_8000000a.xml b/db/xml/leaf_8000000a.xml
>> index 7f73318..433c4b1 100644
>> --- a/db/xml/leaf_8000000a.xml
>> +++ b/db/xml/leaf_8000000a.xml
>> @@ -14,6 +14,11 @@
>>      <ebx>
>>        <bit0  len="32" id="svm_nasid"               desc="Number of address space identifiers (ASID)" />
>>      </ebx>
>> +    <ecx>
>> +      <bit4  len="1"  id="pml"                     desc="Page modification logging (PML)">
>> +        <linux        feature="true"               proc="false" />
>> +      </bit4>
>> +    </ecx>
>>
> 
> Thanks a lot for the patch.
> 
> feature="true" means that the Linux kernel will have an X86_FEATURE_PML
> flag at some point.  I've quickly searched LKML, and I didn't find any
> draft patches for such a flag.

I will be sending a patch on LKML adding X86_FEATURE_PML.

> If that feature flag is not planned, there's no need to send a v2.  I'll
> just set feature="false" before merging to tip.
> 

Regards,
Nikunj