linux-kernel - Re: [PATCH RFC 1/7] x86/virt/tdx: Add SEAMCALL wrapper to enter/exit TDX guest

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Message-ID: <d1b0323f-2458-420b-800e-a26ba6550de7@intel.com>
Date: Fri, 13 Dec 2024 08:16:40 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Adrian Hunter <adrian.hunter@...el.com>, pbonzini@...hat.com,
 seanjc@...gle.com, kvm@...r.kernel.org, dave.hansen@...ux.intel.com
Cc: rick.p.edgecombe@...el.com, kai.huang@...el.com,
 reinette.chatre@...el.com, xiaoyao.li@...el.com,
 tony.lindgren@...ux.intel.com, binbin.wu@...ux.intel.com,
 dmatlack@...gle.com, isaku.yamahata@...el.com, nik.borisov@...e.com,
 linux-kernel@...r.kernel.org, x86@...nel.org, yan.y.zhao@...el.com,
 chao.gao@...el.com, weijiang.yang@...el.com
Subject: Re: [PATCH RFC 1/7] x86/virt/tdx: Add SEAMCALL wrapper to enter/exit
 TDX guest

On 12/11/24 10:43, Adrian Hunter wrote:
...
> -	size = tdvmcall_a0_read(vcpu);
> -	write = tdvmcall_a1_read(vcpu);
> -	port = tdvmcall_a2_read(vcpu);
> +	size  = tdx->vp_enter_out.io_size;
> +	write = tdx->vp_enter_out.io_direction == TDX_WRITE;
> +	port  = tdx->vp_enter_out.io_port;
...> +	case TDVMCALL_IO:
> +		out->io_size		= args.r12;
> +		out->io_direction	= args.r13 ? TDX_WRITE : TDX_READ;
> +		out->io_port		= args.r14;
> +		out->io_value		= args.r15;
> +		break;

I honestly don't understand the need for the abstracted structure to sit
in the middle. It doesn't get stored or serialized or anything, right?
So why have _another_ structure?

Why can't this just be (for instance):

	size = tdx->foo.r12;

?

Basically, you hand around the raw arguments until you need to use them.