From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH v5 16/16] x86/tdx: Add cmdline option to force use of
 ioremap_host_shared
Date: Mon, 11 Oct 2021 14:28:51 -0400
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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>, Peter Zijlstra <peterz@infradead.org>, 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>

On Mon, Oct 11, 2021 at 10:35:18AM -0700, Andi Kleen wrote:
> 
> > Presumably bios code is in arch/x86 and drivers/acpi, right?
> > Up to 200 calls the majority of which is likely private ...
> 
> Yes.
> 
> > 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.
> 
> 
> Yes that's true. For current TDX our target is virtual devices only. But if
> pass through usage will be really wide spread we may need to revisit.
> 
> 
> -Andi

I mean ... it's already wide spread. If we support it with TDX
it will be used with TDX. If we don't then I guess it won't,
exposing this kind of limitation in a userspace visible way isn't great
though. I guess it boils down to the fact that
ioremap_host_shared is just not a great interface, users simply
have no idea whether a given driver uses ioremap.

-- 
MST