Re: [PATCH 5/6] x86/hyperv: Support hypercalls for TDX guests

[Dave Hansen]

On 11/27/22 16:58, Dexuan Cui wrote:
> +u64 hv_tdx_hypercall(u64 control, u64 input_addr, u64 output_addr)
> +{
> +	struct tdx_hypercall_args args = { };
> +
> +	if (!(control & HV_HYPERCALL_FAST_BIT)) {
> +		if (input_addr)
> +			input_addr += ms_hyperv.shared_gpa_boundary;
> +
> +		if (output_addr)
> +			output_addr += ms_hyperv.shared_gpa_boundary;
> +	}

This:

>
https://learn.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/hypercall-interface

makes it sound like HV_HYPERCALL_FAST_BIT says whether arguments go in
registers (fast) or memory (slow).  But this hv_tdx_hypercall() function
looks like it takes addresses only.

*Is* there a register based calling convention to make Hyper-V
hypercalls when running under TDX?

Also, is this the output address manipulation fundamentally different from:

	output_addr = cc_mkdec(output_addr);

?  Decrypted addresses are the shared ones, right?