Re: [PATCH v8 1/2] x86/tdx: Retry TDVMCALL_MAP_GPA() when needed

[Dave Hansen]

On 6/20/23 08:48, Dexuan Cui wrote:
> -static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
> +static bool tdx_map_gpa(phys_addr_t start, phys_addr_t end, bool enc)
>  {
> -	phys_addr_t start = __pa(vaddr);
> -	phys_addr_t end   = __pa(vaddr + numpages * PAGE_SIZE);
> +	const int max_retries_per_page = 3;
> +	struct tdx_hypercall_args args;
> +	u64 map_fail_paddr, ret;
> +	int retry_count = 0;
>  
>  	if (!enc) {
>  		/* Set the shared (decrypted) bits: */
> @@ -718,12 +720,49 @@ static bool tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
>  		end   |= cc_mkdec(0);
>  	}
>  
> -	/*
> -	 * Notify the VMM about page mapping conversion. More info about ABI
> -	 * can be found in TDX Guest-Host-Communication Interface (GHCI),
> -	 * section "TDG.VP.VMCALL<MapGPA>"
> -	 */
> -	if (_tdx_hypercall(TDVMCALL_MAP_GPA, start, end - start, 0, 0))
> +	while (retry_count < max_retries_per_page) {
> +		memset(&args, 0, sizeof(args));
> +		args.r10 = TDX_HYPERCALL_STANDARD;
> +		args.r11 = TDVMCALL_MAP_GPA;
> +		args.r12 = start;
> +		args.r13 = end - start;
> +

What's wrong with:

	while (retry_count < max_retries_per_page) {
		struct tdx_hypercall_args args = {
			.r10 = TDX_HYPERCALL_STANDARD,
			.r11 = TDVMCALL_MAP_GPA,
			.r12 = start,
			.r13 = end - start };

?

Or maybe with the brackets slightly differently arranged.

Why'd you declare all the variables outside the while() loop anyway?