From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D441825740; Fri, 7 Jun 2024 15:12:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717773168; cv=none; b=emYSv6F/OLdBQui1NKGdl7mvvoFO8on3QseSDszFSBgyZG8jRV3tk3TrTlzcoLhPCNCBTznYYp9TpQJxM2qNsvg5iX8zxZ4yC+q88qFphZQn7T6Ax37RkgVBZtTp58qqYpW5fASYxYAsKq85IYM34A82CmaEg5TSijEOS7OCaRU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717773168; c=relaxed/simple; bh=cAI7qnCyUWL53klNBARNIYIAmGI2f8rwVGyKdWH1ehE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=nqApd+zv50x0SsgwQAk3HjCHt9IRFEM0AoaylidxJbHXoUy2k2LQEN5oZ342Hh0oF3orXbRBXdncbQuhu3xhW2BWaIZD+6dfwkV3acZBl1ealmsLnzyjBPIrYvHZAJ85NCMiwiol6UpyypXIaWdB7WnqY1hPLkoIUqwm8V9v4nk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 37809C2BBFC; Fri, 7 Jun 2024 15:12:45 +0000 (UTC) Date: Fri, 7 Jun 2024 16:12:42 +0100 From: Catalin Marinas To: Michael Kelley Cc: Steven Price , "kvm@vger.kernel.org" , "kvmarm@lists.linux.dev" , Marc Zyngier , Will Deacon , James Morse , Oliver Upton , Suzuki K Poulose , Zenghui Yu , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Joey Gouly , Alexandru Elisei , Christoffer Dall , Fuad Tabba , "linux-coco@lists.linux.dev" , Ganapatrao Kulkarni Subject: Re: [PATCH v3 00/14] arm64: Support for running as a guest in Arm CCA Message-ID: References: <20240605093006.145492-1-steven.price@arm.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Jun 07, 2024 at 01:38:15AM +0000, Michael Kelley wrote: > From: Steven Price Sent: Wednesday, June 5, 2024 2:30 AM > > This series adds support for running Linux in a protected VM under the > > Arm Confidential Compute Architecture (CCA). This has been updated > > following the feedback from the v2 posting[1]. Thanks for the feedback! > > Individual patches have a change log for v3. > > > > The biggest change from v2 is fixing set_memory_{en,de}crypted() to > > perform a break-before-make sequence. Note that only the virtual address > > supplied is flipped between shared and protected, so if e.g. a vmalloc() > > address is passed the linear map will still point to the (now invalid) > > previous IPA. Attempts to access the wrong address may trigger a > > Synchronous External Abort. However any code which attempts to access > > the 'encrypted' alias after set_memory_decrypted() is already likely to > > be broken on platforms that implement memory encryption, so I don't > > expect problems. > > In the case of a vmalloc() address, load_unaligned_zeropad() could still > make an access to the underlying pages through the linear address. In > CoCo guests on x86, both the vmalloc PTE and the linear map PTE are > flipped, so the load_unaligned_zeropad() problem can occur only during > the transition between decrypted and encrypted. But even then, the > exception handlers have code to fixup this case and allow everything to > proceed normally. > > I haven't looked at the code in your patches, but do you handle that case, > or somehow prevent it? If we can guarantee that only full a vm_struct area is changed at a time, the vmap guard page would prevent this issue (not sure we can though). Otherwise I think we either change the set_memory_*() code to deal with the other mappings or we handle the exception. We also have potential user mappings, do we need to do anything about them? -- Catalin