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

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Message-ID: <20220223114724.4luaemfi3tyedlvh@black.fi.intel.com>
Date:   Wed, 23 Feb 2022 14:47:24 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Tianyu Lan <ltykernel@...il.com>
Cc:     Borislav Petkov <bp@...en8.de>, Wei Liu <wei.liu@...nel.org>,
        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 Wed, Feb 23, 2022 at 07:02:49PM +0800, Tianyu Lan wrote:
> On 2/23/2022 6:56 PM, Borislav Petkov wrote:
> > On Wed, Feb 23, 2022 at 06:43:40PM +0800, Tianyu Lan wrote:
> > > Hyper-V code check cpuid during runtime and there is no Hyper-V
> > > isolation VM option.
> > 
> > So how does "Current Hyper-V Isolation VM requires AMD_MEM_ENCRYPT" work
> > exactly?
> > 
> > Please explain in detail and not in piecemeal sentences.
> > 
> The kernel in the image needs to select AMD_MEM_ENCRYPT option
> otherwise the kernel can't boot up due to missing SEV support and
> sev_es_ghcb_hv_call() always return error.

If kernel boots under SEV, doesn't it mean we have 'sme_me_mask'
initialized? If it is non zero hv_is_isolation_supported() check in
cc_platform_has() has zero effect as it checked after 'sme_me_mask'.

I still have no idea what is going on.

How SEV related to HyperV isolation? How detection happens? Could you
give full picture?

-- 
 Kirill A. Shutemov