Re: [RFC PATCH 4/4] KVM: SVM: Add Page modification logging support

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

On 8/28/2025 4:03 PM, Huang, Kai wrote:
> On Thu, 2025-08-28 at 12:07 +0530, Nikunj A. Dadhania wrote:
>>
>> On 8/28/2025 5:14 AM, Huang, Kai wrote:
>>> On Mon, 2025-08-25 at 15:20 +0000, Nikunj A Dadhania wrote:
>>>> +	if (pml) {
>>>> +		svm->pml_page = snp_safe_alloc_page();
>>>> +		if (!svm->pml_page)
>>>> +			goto error_free_vmsa_page;
>>>> +	}
>>>
>>> I didn't see this yesterday.  Is it mandatory for AMD PML to use
>>> snp_safe_alloc_page() to allocate the PML buffer, or we can also use
>>> normal page allocation API?
>>
>> As it is dependent on HvInUseWrAllowed, I need to use snp_safe_alloc_page().
> 
> So the patch 2 is actually a dependent for PML?

Not really, if the patch 2 is not there, the 2MB alignment workaround will be
applied to PML page allocation.

> 
>>
>> Tom?
>>
>>> VMX PML just uses alloc_pages().  I was thinking the page allocation/free
>>> code could be moved to x86 common as shared code too.
>> Got that, because of the above requirement, I was going to share the variable
>> (pml_page) but do the allocation in the vmx/svm code.
>>
> 
> If AMD and VMX PML cannot share PML buffer allocation/free code, my desire
> to share 'pml_pg' is becoming less, but I guess I kinda still think it's
> better to share the buffer pointer. :-)
Sure, will add in my next revision.

Regards
Nikunj