linux-kernel - Re: [PATCH 1/4] x86/hyperv: Add missing ARCH_HAS_CC

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Message-ID: <4769a3c0-449b-184a-5c61-a0e155f9c5b4@gmail.com>
Date:   Wed, 23 Feb 2022 15:04:41 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     Borislav Petkov <bp@...en8.de>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Wei Liu <wei.liu@...nel.org>
Cc:     tglx@...utronix.de, mingo@...hat.com, dave.hansen@...el.com,
        luto@...nel.org, peterz@...radead.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com, aarcange@...hat.com,
        ak@...ux.intel.com, dan.j.williams@...el.com, david@...hat.com,
        hpa@...or.com, jmattson@...gle.com, seanjc@...gle.com,
        thomas.lendacky@....com, brijesh.singh@....com, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>
Subject: Re: [PATCH 1/4] x86/hyperv: Add missing ARCH_HAS_CC_PLATFORM
 dependency

On 2/23/2022 4:08 AM, Borislav Petkov wrote:
> On Tue, Feb 22, 2022 at 09:57:37PM +0300, Kirill A. Shutemov wrote:
>> On x86, cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT) supposes to return
>> true for HyperV if isolation is supported. But it only does it if the
>> kernel is compiled with AMD_MEM_ENCRYPT enabled.
>>
>> It happens due to missed ARCH_HAS_CC_PLATFORM dependency. Without
>> ARCH_HAS_CC_PLATFORM enabled, cc_platform_has() always returns false.
>>
>> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
>> Cc: "K. Y. Srinivasan" <kys@...rosoft.com>
>> Cc: Haiyang Zhang <haiyangz@...rosoft.com>
>> Cc: Stephen Hemminger <sthemmin@...rosoft.com>
>> Cc: Wei Liu <wei.liu@...nel.org>
>> Cc: Dexuan Cui <decui@...rosoft.com>
>> Cc: Tianyu Lan <Tianyu.Lan@...rosoft.com>
>> ---
>>   drivers/hv/Kconfig | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
>> index 0747a8f1fcee..424d3f0751dc 100644
>> --- a/drivers/hv/Kconfig
>> +++ b/drivers/hv/Kconfig
>> @@ -8,6 +8,7 @@ config HYPERV
>>   		|| (ARM64 && !CPU_BIG_ENDIAN))
>>   	select PARAVIRT
>>   	select X86_HV_CALLBACK_VECTOR if X86
>> +	select ARCH_HAS_CC_PLATFORM if x86
>>   	select VMAP_PFN
>>   	help
>>   	  Select this option to run Linux as a Hyper-V client operating
>> -- 
> 
> Good catch.
> 
> I'm guessing this needs
> 
> Fixes: c789b90a6904 ("x86/hyper-v: Add hyperv Isolation VM check in the cc_platform_has()")
> 
> which added hyperv_cc_platform_has() and which needs to go to Linus now,
> as an urgent fix for 5.17 as that patch came into 5.17-rc1.
> 
> Wei?
> 

Hi Borias, wei and Kill:
       Current Hyper-V Isolation VM requires AMD_MEM_ENCRYPT option 
which selects ARCH_HAS_CC_PLATFORM. Linux guest can't boot up without 
AMD_MEM_ENCRYPT option. So this is why not select ARCH_HAS_CC_PLATFORM
here.