Re: [PATCH v8 23/30] KVM: selftests: Add functions to allow mapping as shared

[Binbin Wu <binbin.wu@linux.intel.com>]

On 8/8/2025 4:16 AM, Sagi Shahar wrote:
> From: Ackerley Tng <ackerleytng@google.com>
>
> virt_map() enforces a private mapping for private memory. Introduce
> virt_map_shared() that creates a shared mapping for private as
> well as shared memory. This way, the TD does not have to remap its
> page tables at runtime.
>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>
> Signed-off-by: Sagi Shahar <sagis@google.com>
> ---
>   .../testing/selftests/kvm/include/kvm_util.h  | 23 +++++++++++++
>   tools/testing/selftests/kvm/lib/kvm_util.c    | 34 +++++++++++++++++++
>   .../testing/selftests/kvm/lib/x86/processor.c | 15 ++++++--
>   3 files changed, 70 insertions(+), 2 deletions(-)
>
[...]
>   
> -void __virt_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr, int level)
> +static void ___virt_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
> +			   int level, bool protected)
>   {
>   	const uint64_t pg_size = PG_LEVEL_SIZE(level);
>   	uint64_t *pml4e, *pdpe, *pde;
> @@ -231,17 +232,27 @@ void __virt_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr, int level)
>   	 * Neither SEV nor TDX supports shared page tables, so only the final
>   	 * leaf PTE needs manually set the C/S-bit.
>   	 */
> -	if (vm_is_gpa_protected(vm, paddr))

Since the original code has already create shared/private mapping based on the
paddr, why not just use virt_map() and shared GPA as paddr, then no need to
duplicate the code?

> +	if (protected)
>   		*pte |= vm->arch.c_bit;
>   	else
>   		*pte |= vm->arch.s_bit;
>   }
>   
> +void __virt_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr, int level)
> +{
> +	___virt_pg_map(vm, vaddr, paddr, level, vm_is_gpa_protected(vm, paddr));
> +}
> +
>   void virt_arch_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr)
>   {
>   	__virt_pg_map(vm, vaddr, paddr, PG_LEVEL_4K);
>   }
>   
> +void virt_arch_pg_map_shared(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr)
> +{
> +	___virt_pg_map(vm, vaddr, paddr, PG_LEVEL_4K, false);
> +}
> +
>   void virt_map_level(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
>   		    uint64_t nr_bytes, int level)
>   {