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

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Date:   Wed, 23 Nov 2022 10:18:09 -0800
From:   Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>,
        Dexuan Cui <decui@...rosoft.com>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "arnd@...db.de" <arnd@...db.de>, "bp@...en8.de" <bp@...en8.de>,
        "brijesh.singh@....com" <brijesh.singh@....com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "jane.chu@...cle.com" <jane.chu@...cle.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        KY Srinivasan <kys@...rosoft.com>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "luto@...nel.org" <luto@...nel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "seanjc@...gle.com" <seanjc@...gle.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "tony.luck@...el.com" <tony.luck@...el.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/6] x86/hyperv: Support hypercalls for TDX guests



On 11/23/22 6:47 AM, Kirill A. Shutemov wrote:
> On Wed, Nov 23, 2022 at 02:14:58AM +0000, Dexuan Cui wrote:
>>> From: Dave Hansen <dave.hansen@...el.com>
>>> Sent: Monday, November 21, 2022 12:05 PM
>>> [...]
>>>>  #ifdef CONFIG_X86_64
>>>> +#if CONFIG_INTEL_TDX_GUEST
>>>> +	if (hv_isolation_type_tdx()) {
>>>
>>>>  #ifdef CONFIG_X86_64
>>>> +#if CONFIG_INTEL_TDX_GUEST
>>>> +	if (hv_isolation_type_tdx())
>>>
>>>>  #ifdef CONFIG_X86_64
>>>> +#if CONFIG_INTEL_TDX_GUEST
>>>> +	if (hv_isolation_type_tdx())
>>>> +		return __tdx_ms_hv_hypercall(control, input2, input1);
>>>
>>> See any common patterns there?
>>>
>>> The "no #ifdef's in C files" rule would be good to apply here.  Please
>>> do one #ifdef in a header.
>>
>> Sorry, I should use #ifdef rather than #if. I'll fix it like the below.
> 
> No, can we hide preprocessor hell inside hv_isolation_type_tdx()?
> 
> Like make it return false for !CONFIG_INTEL_TDX_GUEST and avoid all
> #if/#ifdefs in C file.

There is a weak reference to hv_isolation_type_tdx() which returns false
by default. So defining the hv_isolation_type_tdx within
#ifdef CONFIG_INTEL_TDX_GUEST would be enough.

> 
> 

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer