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Tsirkin" To: Andi Kleen Subject: Re: [PATCH v5 16/16] x86/tdx: Add cmdline option to force use of ioremap_host_shared Message-ID: <20211012171846-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> <20211011142330-mutt-send-email-mst@kernel.org> <4fe8d60a-2522-f111-995c-dcbefd0d5e31@linux.intel.com> <20211012165705-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: Kuppuswamy Sathyanarayanan , Kuppuswamy Sathyanarayanan , Peter Zijlstra , linux-pci@vger.kernel.org, linux-mips@vger.kernel.org, James E J Bottomley , Dave Hansen , Peter H Anvin , sparclinux@vger.kernel.org, Thomas Gleixner , Andrea Arcangeli , Jonathan Corbet , Helge Deller , x86@kernel.org, Ingo Molnar , linux-arch@vger.kernel.org, Arnd Bergmann , Tony Luck , Borislav Petkov , Andy Lutomirski , Josh Poimboeuf , Bjorn Helgaas , Dan Williams , virtualization@lists.linux-foundation.org, Richard Henderson , Thomas Bogendoerfer , linux-parisc@vger.kernel.org, Sean Christopherson , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org, Paolo Bonzini , "David S . Miller" , Kirill Shutemov X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Tue, Oct 12, 2021 at 02:18:01PM -0700, Andi Kleen wrote: > > > Interesting. VT-d tradeoffs ... what are they? > > The connection to the device is not encrypted and also not authenticated. > > This is different that even talking to the (untrusted) host through shared > memory where you at least still have a common key. Well it's different sure enough but how is talking to host less secure? Cold boot attacks and such? > > Allowing hypervisor to write into BIOS looks like it will > > trivially lead to code execution, won't it? > > This is not about BIOS code executing. While the guest firmware runs it is > protected of course. This is for BIOS structures like ACPI tables that are > mapped by Linux. While AML can run byte code it can normally not write to > arbitrary memory. I thought you basically create an OperationRegion of SystemMemory type, and off you go. Maybe the OSPM in Linux is clever and protects some memory, I wouldn't know. > The risk is more that all the Linux code dealing with this hasn't been > hardened to deal with malicious input. > > -Andi -- MST _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization