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

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Date:   Tue, 22 Feb 2022 21:08:02 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "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 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?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette