linux-kernel - Re: [PATCH v19 036/130] KVM: TDX: x86: Add ioctl to get TDX systemwide parameters

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Date: Wed, 24 Apr 2024 10:30:45 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Yamahata,
 Isaku" <isaku.yamahata@...el.com>
CC: "Zhang, Tina" <tina.zhang@...el.com>, "seanjc@...gle.com"
	<seanjc@...gle.com>, "Yuan, Hang" <hang.yuan@...el.com>, "Chen, Bo2"
	<chen.bo@...el.com>, "sagis@...gle.com" <sagis@...gle.com>,
	"isaku.yamahata@...il.com" <isaku.yamahata@...il.com>, "Aktas, Erdem"
	<erdemaktas@...gle.com>, "pbonzini@...hat.com" <pbonzini@...hat.com>,
	"sean.j.christopherson@...el.com" <sean.j.christopherson@...el.com>
Subject: Re: [PATCH v19 036/130] KVM: TDX: x86: Add ioctl to get TDX
 systemwide parameters

On Mon, 2024-02-26 at 00:25 -0800, isaku.yamahata@...el.com wrote:
> --- a/arch/x86/kvm/vmx/tdx.h
> +++ b/arch/x86/kvm/vmx/tdx.h
> @@ -3,6 +3,9 @@
>  #define __KVM_X86_TDX_H
>  
>  #ifdef CONFIG_INTEL_TDX_HOST
> +
> +#include "tdx_ops.h"
> +
>  struct kvm_tdx {
>  	struct kvm kvm;
>  	/* TDX specific members follow. */

I am consistently hitting build error for the middle patches in our
internal tree, mostly because of this madness of header file inclusion.

I found the above inclusion of "tdx_ops.h" in "tdx.h" just out of blue.

We have

 - "tdx_arch.h"
 - "tdx_errno.h"
 - "tdx_ops.h"
 - "tdx.h"

The first two can be included by the "tdx.h", so that we can have a rule
for C files to just include "tdx.h", i.e., the C files should never need
to include the first two explicitly.

The "tdx_ops.h" is a little bit confusing.  I _think_ the purpose of it is
to only contain SEAMCALL wrappers.  But I am not sure whether it can be
included by any C file directly.

Based on above code change, I _think_ the intention is to also embed it to
"tdx.h", so the C files should just include "tdx.h".

But based on Sean's comments, the SEAMCALL wrappers will be changed to
take 'struct kvm_tdx *' and 'struct vcpu_tdx *', so they need the
declaration of those structures which are in "tdx.h".

I think we can just make a rule that, "tdx_ops.h" should never be directly
included by any C file, instead, we include "tdx_ops.h" into "tdx.h"
somewhere after declaration of 'struct kvm_tdx' and 'struct vcpu_tdx'.

And such inclusion should happen when the "tdx_ops.h" is introduced.

Am I missing anything?