Re: [PATCH v15 10/21] KVM: x86/mmu: Generalize private_max_mapping_level x86 op to max_mapping_level

[Xiaoyao Li <xiaoyao.li@intel.com>]

On 7/18/2025 12:27 AM, Fuad Tabba wrote:
> From: Ackerley Tng <ackerleytng@google.com>
> 
> Generalize the private_max_mapping_level x86 operation to
> max_mapping_level.
> 
> The private_max_mapping_level operation allows platform-specific code to
> limit mapping levels (e.g., forcing 4K pages for certain memory types).
> While it was previously used exclusively for private memory, guest_memfd
> can now back both private and non-private memory. Platforms may have
> specific mapping level restrictions that apply to guest_memfd memory
> regardless of its privacy attribute. Therefore, generalize this
> operation.
> 
> Rename the operation: Removes the "private" prefix to reflect its
> broader applicability to any guest_memfd-backed memory.
> 
> Pass kvm_page_fault information: The operation is updated to receive a
> struct kvm_page_fault object instead of just the pfn. This provides
> platform-specific implementations (e.g., for TDX or SEV) with additional
> context about the fault, such as whether it is private or shared,
> allowing them to apply different mapping level rules as needed.
> 
> Enforce "private-only" behavior (for now): Since the current consumers
> of this hook (TDX and SEV) still primarily use it to enforce private
> memory constraints, platform-specific implementations are made to return
> 0 for non-private pages. A return value of 0 signals to callers that
> platform-specific input should be ignored for that particular fault,
> indicating no specific platform-imposed mapping level limits for
> non-private pages. This allows the core MMU to continue determining the
> mapping level based on generic rules for such cases.
> 
> Acked-by: David Hildenbrand <david@redhat.com>
> Suggested-by: Sean Christoperson <seanjc@google.com>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>
> Signed-off-by: Fuad Tabba <tabba@google.com>

Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>