Re: [PATCH v5 08/14] x86/mm: Add generic guest initialization hook

Dave Hansen
2023-10-30T17:23:13Z

On 10/29/23 23:36, Nikunj A Dadhania wrote:
> diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
> index a37ebd3b4773..a07985a96ca5 100644
> --- a/arch/x86/kernel/x86_init.c
> +++ b/arch/x86/kernel/x86_init.c
> @@ -136,6 +136,7 @@ static bool enc_status_change_finish_noop(unsigned long vaddr, int npages, bool
> static bool enc_tlb_flush_required_noop(bool enc) { return false; }
> static bool enc_cache_flush_required_noop(void) { return false; }
> static bool is_private_mmio_noop(u64 addr) {return false; }
> +static void enc_init_noop(void) { }
>
> struct x86_platform_ops x86_platform __ro_after_init = {
> .calibrate_cpu = native_calibrate_cpu_early,
> @@ -158,6 +159,7 @@ struct x86_platform_ops x86_platform __ro_after_init = {
> .enc_status_change_finish = enc_status_change_finish_noop,
> .enc_tlb_flush_required = enc_tlb_flush_required_noop,
> .enc_cache_flush_required = enc_cache_flush_required_noop,
> + .enc_init = enc_init_noop,
> },
> };
>
> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index 9f27e14e185f..01abecc9a774 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -84,5 +84,8 @@ void __init mem_encrypt_init(void)
> /* Call into SWIOTLB to update the SWIOTLB DMA buffers */
> swiotlb_update_mem_attributes();
>
> + if (x86_platform.guest.enc_init)
> + x86_platform.guest.enc_init();
> +
> print_mem_encrypt_feature_info();
> }

How does '.enc_init' ever get set to NULL? Isn't the point of having
and using a 'noop' function so that you don't have to do NULL checks?