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Tsirkin" To: Kuppuswamy Sathyanarayanan Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Peter Zijlstra , Andy Lutomirski , Bjorn Helgaas , Richard Henderson , Thomas Bogendoerfer , James E J Bottomley , Helge Deller , "David S . Miller" , Arnd Bergmann , Jonathan Corbet , Paolo Bonzini , David Hildenbrand , Andrea Arcangeli , Josh Poimboeuf , Peter H Anvin , Dave Hansen , Tony Luck , Dan Williams , Andi Kleen , Kirill Shutemov , Sean Christopherson , Kuppuswamy Sathyanarayanan , 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: <20211009070132-mutt-send-email-mst@kernel.org> References: <20211009003711.1390019-1-sathyanarayanan.kuppuswamy@linux.intel.com> <20211009003711.1390019-17-sathyanarayanan.kuppuswamy@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211009003711.1390019-17-sathyanarayanan.kuppuswamy@linux.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Fri, Oct 08, 2021 at 05:37:11PM -0700, Kuppuswamy Sathyanarayanan wrote: > + ioremap_force_shared= [X86_64, CCG] > + Force the kernel to use shared memory mappings which do > + not use ioremap_host_shared/pcimap_host_shared to opt-in > + to shared mappings with the host. This feature is mainly > + used by a confidential guest when enabling new drivers > + without proper shared memory related changes. Please note > + that this option might also allow other non explicitly > + enabled drivers to interact with the host in confidential > + guest, which could cause other security risks. This option > + will also cause BIOS data structures to be shared with the > + host, which might open security holes. > + > io7= [HW] IO7 for Marvel-based Alpha systems > See comment before marvel_specify_io7 in > arch/alpha/kernel/core_marvel.c. The connection is quite unfortunate IMHO. Can't there be an option that unbreaks drivers *without* opening up security holes by making BIOS shared? -- MST