linux-kernel - Re: [RFC v2-fix-v2 1/1] x86: Introduce generic protected guest abstraction

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Date:   Wed, 9 Jun 2021 16:32:46 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        linux-kernel@...r.kernel.org,
        Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [RFC v2-fix-v2 1/1] x86: Introduce generic protected guest
 abstraction

On Wed, Jun 09, 2021 at 07:01:13AM -0700, Kuppuswamy, Sathyanarayanan wrote:
> I am still not clear. What happens when a driver which includes
> linux/protected-guest.h is compiled for non-x86 arch (s390 or arm64)?

I was wondering what felt weird: why is prot{ected,}_guest_has() in a
generic linux/ namespace header and not in an asm/ one?

I think the proper way is for the other arches should be to provide
their own prot_guest_has() implementation which generic code uses and
the generic header would contain only the PR_GUEST_* defines.

Take ioremap() as an example:

arch/x86/include/asm/io.h
arch/arm64/include/asm/io.h
arch/s390/include/asm/io.h
...

and pretty much every arch has that arch-specific io.h header which
defines ioremap() and generic code includes include/linux/io.h which
includes the respective asm/io.h header so that users can call the
respective ioremap() implementation.

prot_guest_has() sounds just the same to me.

Better?

-- 
Regards/Gruss,
    Boris.

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