linux-kernel - Re: [PATCH] x86/sev: Make SEV

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Message-ID: <20250305165502.GLZ8iB5kAtQmW6fu1F@fat_crate.local>
Date: Wed, 5 Mar 2025 17:55:02 +0100
From: Borislav Petkov <bp@...en8.de>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Joerg Roedel <jroedel@...e.de>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Ingo Molnar <mingo@...nel.org>, Joerg Roedel <joro@...tes.org>,
	x86@...nel.org, hpa@...or.com,
	Tom Lendacky <thomas.lendacky@....com>,
	Nikunj A Dadhania <nikunj@....com>, linux-kernel@...r.kernel.org,
	Larry.Dewey@....com
Subject: Re: [PATCH] x86/sev: Make SEV_STATUS available via SYSFS

On Wed, Mar 05, 2025 at 08:40:29AM -0800, Dave Hansen wrote:
> TDX guests have CPUID to tell them that they're running that way.

And those CPUID leafs cannot be modified or intercepted or so by the
hypervisor?

> TDX hosts are much more arcane. You can't _actually_ know that it's a
> TDX host until you actually start making successful SEAMCALLs and the
> TDX module answers them. But we fudge it by just looking at
> MSR_IA32_MKTME_KEYID_PARTITIONING at boot and assuming that anything
> with that MSR will be able to be a TDX host.

Fun. :)

> We've just got X86_FEATUREs for hosts and guests:
> 
> 	#define X86_FEATURE_TDX_HOST_PLATFORM ( 7*32+ 7)
> 	#define X86_FEATURE_TDX_GUEST ( 8*32+22)
> 
> and that's it.

And there are no new ones coming down the pipe?

> Folks certainly _want_ something in sysfs to dump the TDX module version
> and so forth, but we've resisted the urge so far.

Perhaps now is the time do design something together...

I was thinking

/sys/guest/...

or something tied to the x86_platform gunk so that we can stick always some
info there about any platform arch/x86/ has detected and is running on...

Hmmm.

-- 
Regards/Gruss,
    Boris.

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