linux-kernel - Re: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range to map as encrypted

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Message-ID: <Y++VSZNAX9Cstbqo@zn.tnic>
Date:   Fri, 17 Feb 2023 15:55:05 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Dave Hansen <dave.hansen@...el.com>,
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Subject: Re: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range
 to map as encrypted

On Fri, Feb 17, 2023 at 06:16:56AM +0000, Michael Kelley (LINUX) wrote:
> Is that consistent with your thinking, or is the whole
> cc_platform_has() approach problematic, including for the existing SEV
> flavors and for TDX?

The confidential computing attributes are, yes, features. I've been
preaching since the very beginning that vTOM *is* *also* one such
feature. It is a feature bit in sev_features, for chrissakes. So by that
logic, those SEV-SNP HyperV guests should return true when

	cc_platform_has(CC_ATTR_GUEST_SEV_SNP_VTOM);

is tested.

But Sean doesn't like that.

If the access method to the IO-APIC and vTPM are specific to the
HyperV's vTOM implementation, then I don't mind if this were called

	cc_platform_has(CC_ATTR_GUEST_HYPERV_VTOM);

Frankly, I don't see any other enlightened guest using vTOM except
HyperV's but virt folks have managed to surprise me in the past too.

In any case, a single flag which is specific to that guest type is fine
too.

It feels like we're running in circles by now... ;-\

-- 
Regards/Gruss,
    Boris.

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