Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Mon, 11 Oct 2021 14:28:51 -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>,
        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>,
        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>,
        Sean Christopherson <seanjc@google.com>,
        Kuppuswamy Sathyanarayanan <knsathya@kernel.org>,
        x86@kernel.org, linux-kernel@vger.kernel.org,
        linux-pci@vger.kernel.org, linux-alpha@vger.kernel.org,
        linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org,
        sparclinux@vger.kernel.org, linux-arch@vger.kernel.org,
        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
Message-ID: <20211011142330-mutt-send-email-mst@kernel.org>
References: <20211009003711.1390019-1-sathyanarayanan.kuppuswamy@linux.intel.com>
 <20211009003711.1390019-17-sathyanarayanan.kuppuswamy@linux.intel.com>
 <20211009070132-mutt-send-email-mst@kernel.org>
 <8c906de6-5efa-b87a-c800-6f07b98339d0@linux.intel.com>
 <20211011075945-mutt-send-email-mst@kernel.org>
 <9d0ac556-6a06-0f2e-c4ff-0c3ce742a382@linux.intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <9d0ac556-6a06-0f2e-c4ff-0c3ce742a382@linux.intel.com>
Precedence: bulk

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