Re: [PATCH v10 11/16] KVM: x86: Compute max_mapping_level with input from guest_memfd

[David Hildenbrand <david@redhat.com>]

On 27.05.25 20:02, Fuad Tabba wrote:
> From: Ackerley Tng <ackerleytng@google.com>
> 
> This patch adds kvm_gmem_max_mapping_level(), which always returns
> PG_LEVEL_4K since guest_memfd only supports 4K pages for now.
> 
> When guest_memfd supports shared memory, max_mapping_level (especially
> when recovering huge pages - see call to __kvm_mmu_max_mapping_level()
> from recover_huge_pages_range()) should take input from
> guest_memfd.
> 
> Input from guest_memfd should be taken in these cases:
> 
> + if the memslot supports shared memory (guest_memfd is used for
>    shared memory, or in future both shared and private memory) or
> + if the memslot is only used for private memory and that gfn is
>    private.
> 
> If the memslot doesn't use guest_memfd, figure out the
> max_mapping_level using the host page tables like before.
> 
> This patch also refactors and inlines the other call to
> __kvm_mmu_max_mapping_level().
> 
> In kvm_mmu_hugepage_adjust(), guest_memfd's input is already
> provided (if applicable) in fault->max_level. Hence, there is no need
> to query guest_memfd.
> 
> lpage_info is queried like before, and then if the fault is not from
> guest_memfd, adjust fault->req_level based on input from host page
> tables.
> 

> Signed-off-by: Ackerley Tng <ackerleytng@google.com>

Should there be a Co-developed-by?

> Signed-off-by: Fuad Tabba <tabba@google.com>
> ---

LGTM, but I am not particularly an expert on that code. Having some 
feedback from Sean Et. al would be great :)

-- 
Cheers,

David / dhildenb