netdev - RE: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range to map as encrypted

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Date:   Fri, 17 Feb 2023 06:16:56 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     Borislav Petkov <bp@...en8.de>
CC:     Sean Christopherson <seanjc@...gle.com>,
        Dave Hansen <dave.hansen@...el.com>,
        "hpa@...or.com" <hpa@...or.com>, KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "luto@...nel.org" <luto@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
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        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
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        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
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        "jane.chu@...cle.com" <jane.chu@...cle.com>,
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        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>
Subject: RE: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range
 to map as encrypted



From: Borislav Petkov <bp@...en8.de> Sent: Thursday, February 16, 2023 9:07 AM
> 
> ... here.
> 
> We need a single way to test for this guest type and stick with it.
> 
> I'd like for all guest types we support to be queried in a plain and
> simple way.
> 
> Not:
> 
> * CC_ATTR_GUEST_MEM_ENCRYPT
> 
> * x86_platform.hyper.is_private_mmio(addr)
> 
> * CC_ATTR_PARAVISOR
> 
> to mean three different aspects of SEV-SNP guests using vTOM on Hyper-V.
> 
> This is going to be a major mess which we won't support.
> 

OK, I'm trying to figure out where to go next.  I've been following the pattern
set by the SEV/SEV-ES/SEV-SNP and TDX platforms in the cc_platform_has()
function.   Each platform returns "true" for multiple CC_ATTR_* values,
and those CC_ATTR_* values are tested in multiple places throughout
kernel code.  Some CC_ATTR_* values are shared by multiple platforms
(like CC_ATTR_GUEST_MEM_ENCRYPT) and some are unique to a particular
platform (like CC_ATTR_HOTPLUG_DISABLED).  For the CC_ATTR_* values
that are shared, the logic of which platforms they apply to occurs once in
cc_platform_has() rather than scattered and duplicated throughout the
kernel, which makes sense.  Any given platform is not represented by a
single CC_ATTR_* value, but by multiple ones.  Each CC_ATTR_* value 
essentially represents a chunk of kernel functionality that one or more
platforms need, and the platform indicates its need by cc_platform_has()
returning "true" for that value.

So I've been trying to apply the same pattern to the SNP vTOM sub-case
of SEV-SNP.   Is that consistent with your thinking, or is the whole
cc_platform_has() approach problematic, including for the existing
SEV flavors and for TDX?

Michael