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Date:   Mon, 11 Oct 2021 08:04:16 -0400
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     Andi Kleen <ak@linux.intel.com>
Cc:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
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        Andy Lutomirski <luto@kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Richard Henderson <rth@twiddle.net>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        James E J Bottomley <James.Bottomley@hansenpartnership.com>,
        Helge Deller <deller@gmx.de>,
        "David S . Miller" <davem@davemloft.net>,
        Arnd Bergmann <arnd@arndb.de>,
        Jonathan Corbet <corbet@lwn.net>,
        Paolo Bonzini <pbonzini@redhat.com>,
        David Hildenbrand <david@redhat.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Peter H Anvin <hpa@zytor.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Kirill Shutemov <kirill.shutemov@linux.intel.com>,
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        Kuppuswamy Sathyanarayanan <knsathya@kernel.org>,
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        linux-doc@vger.kernel.org,
        virtualization@lists.linux-foundation.org
Subject: Re: [PATCH v5 16/16] x86/tdx: Add cmdline option to force use of
 ioremap_host_shared
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On Sun, Oct 10, 2021 at 07:39:55PM -0700, Andi Kleen wrote:
> 
> > The connection is quite unfortunate IMHO.
> > Can't there be an option
> > that unbreaks drivers *without* opening up security holes by
> > making BIOS shared?
> 
> That would require new low level APIs that distinguish both cases, and a
> tree sweep.
> 
> 
> -Andi

Presumably bios code is in arch/x86 and drivers/acpi, right?
Up to 200 calls the majority of which is likely private ...

I don't have better ideas but the current setup will just
result in people making their guests vulnerable whenever they
want to allow device pass-through.

-- 
MST