From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3052CC54E66 for ; Tue, 12 Mar 2024 10:33:36 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=WhjR2Xpx; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4Tv93L5ssgz3dSn for ; Tue, 12 Mar 2024 21:33:34 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=WhjR2Xpx; dkim-atps=neutral Received: from gandalf.ozlabs.org (gandalf.ozlabs.org [150.107.74.76]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4Tv92X4rV0z3cN6 for ; Tue, 12 Mar 2024 21:32:52 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ellerman.id.au; s=201909; t=1710239571; bh=WAJdAg2kSVxd3biZa1Q3GiQlxvq8aCBQjEnXtrdMZQc=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=WhjR2XpxEiPKrQ1UxYUIKDVVtrEY/A16XeUHH+p3tVkIPYZbSPSK7huCOZ9+EGJrn jmmBglW76EAQAZA0xMrdgDmIsfa7yJuLAhdZ4QjZXTuYz6VdgH0pQipie0omSQtxi3 x0OIJJhmBV1opHy0gGEjVxsiPU5Jz2Cmnu8bJ7d2HyT/sVcCWrZB4t+jwDCorJ/Z7g Uq0eSwfQ4vOLUiMhEG5uX0nWXbzcfKfjE5DJA+PEHbyCPfhMCkz1u54ZfiRFBIN3tS QSJqAF3zo/BRQ3x+xIdcnEKIFkh31tl6eZziDO+eCpeXZtS/mbdIf6EcPtKcnImw6k DwgrCoGA7JCEA== Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 4Tv92W2Nl8z4wcq; Tue, 12 Mar 2024 21:32:51 +1100 (AEDT) From: Michael Ellerman To: Rob Herring , Stefan Berger Subject: Re: [PATCH 1/2] powerpc/prom_init: Replace linux,sml-base/sml-size with linux,sml-log In-Reply-To: <20240308205751.GA1249866-robh@kernel.org> References: <20240306155511.974517-1-stefanb@linux.ibm.com> <20240306155511.974517-2-stefanb@linux.ibm.com> <87jzmenx2c.fsf@mail.lhotse> <20240307215214.GB3110385-robh@kernel.org> <851536a5-ad8f-4d65-8c33-707e2fe762df@linux.ibm.com> <20240308205751.GA1249866-robh@kernel.org> Date: Tue, 12 Mar 2024 21:32:50 +1100 Message-ID: <87a5n34u5p.fsf@mail.lhotse> MIME-Version: 1.0 Content-Type: text/plain X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: rnsastry@linux.ibm.com, linux-kernel@vger.kernel.org, jarkko@kernel.org, linux-integrity@vger.kernel.org, viparash@in.ibm.com, linuxppc-dev@lists.ozlabs.org, peterhuewe@gmx.de Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Rob Herring writes: > On Fri, Mar 08, 2024 at 07:23:35AM -0500, Stefan Berger wrote: >> On 3/7/24 16:52, Rob Herring wrote: >> > On Thu, Mar 07, 2024 at 09:41:31PM +1100, Michael Ellerman wrote: >> > > Stefan Berger writes: >> > > > linux,sml-base holds the address of a buffer with the TPM log. This >> > > > buffer may become invalid after a kexec and therefore embed the whole TPM >> > > > log in linux,sml-log. This helps to protect the log since it is properly >> > > > carried across a kexec with both of the kexec syscalls. >> > > > >> > > > Signed-off-by: Stefan Berger >> > > > --- >> > > > arch/powerpc/kernel/prom_init.c | 8 ++------ >> > > > 1 file changed, 2 insertions(+), 6 deletions(-) >> > > > >> >> > >> > >> > > Also adding the new linux,sml-log property should be accompanied by a >> > > change to the device tree binding. >> > > >> > > The syntax is not very obvious to me, but possibly something like? >> > > >> > > diff --git a/Documentation/devicetree/bindings/tpm/ibm,vtpm.yaml b/Documentation/devicetree/bindings/tpm/ibm,vtpm.yaml >> > > index 50a3fd31241c..cd75037948bc 100644 >> > > --- a/Documentation/devicetree/bindings/tpm/ibm,vtpm.yaml >> > > +++ b/Documentation/devicetree/bindings/tpm/ibm,vtpm.yaml >> > > @@ -74,8 +74,6 @@ required: >> > > - ibm,my-dma-window >> > > - ibm,my-drc-index >> > > - ibm,loc-code >> > > - - linux,sml-base >> > > - - linux,sml-size >> > >> > Dropping required properties is an ABI break. If you drop them, an older >> > OS version won't work. >> >> 1) On PowerVM and KVM on Power these two properties were added in the Linux >> code. I replaced the creation of these properties with creation of >> linux,sml-log (1/2 in this series). I also replaced the handling of >> these two (2/2 in this series) for these two platforms but leaving it for >> powernv systems where the firmware creates these. > > Okay, I guess your case is not a ABI break if the kernel is populating > it and the same kernel consumes it. > > You failed to answer my question on using /reserved-memory. Again, why > can't that be used? That is the standard way we prevent chunks of memory > from being clobbered. Yes I think that would mostly work. I don't see support for /reserved-memory in kexec-tools, so that would need fixing I think. My logic was that the memory is not special. It's just a buffer we allocated during early boot to store the log. There isn't anything else in the system that relies on that memory remaining untouched. So it seemed cleaner to just put the log in the device tree, rather than a pointer to it. Having the log external to the device tree creates several problems, like the crash kernel region colliding with it, it being clobbered by kexec, etc. cheers