Re: [PATCH 1/4] x86/hyperv: Add missing ARCH_HAS_CC_PLATFORM dependency

[Tianyu Lan <ltykernel@gmail.com>]

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@linux.intel.com>
>> Cc: "K. Y. Srinivasan" <kys@microsoft.com>
>> Cc: Haiyang Zhang <haiyangz@microsoft.com>
>> Cc: Stephen Hemminger <sthemmin@microsoft.com>
>> Cc: Wei Liu <wei.liu@kernel.org>
>> Cc: Dexuan Cui <decui@microsoft.com>
>> Cc: Tianyu Lan <Tianyu.Lan@microsoft.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.