From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bmailout3.hostsharing.net (bmailout3.hostsharing.net [176.9.242.62]) (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 3DAE0347C7 for ; Mon, 9 Oct 2023 14:02:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=wunner.de Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=h08.hostsharing.net Authentication-Results: smtp.subspace.kernel.org; dkim=none Received: from h08.hostsharing.net (h08.hostsharing.net [IPv6:2a01:37:1000::53df:5f1c:0]) (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 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "*.hostsharing.net", Issuer "RapidSSL Global TLS RSA4096 SHA256 2022 CA1" (verified OK)) by bmailout3.hostsharing.net (Postfix) with ESMTPS id E4D27100D943F; Mon, 9 Oct 2023 16:02:33 +0200 (CEST) Received: by h08.hostsharing.net (Postfix, from userid 100393) id B2D8A30D471; Mon, 9 Oct 2023 16:02:33 +0200 (CEST) Date: Mon, 9 Oct 2023 16:02:33 +0200 From: Lukas Wunner To: Alexey Kardashevskiy Cc: Bjorn Helgaas , David Howells , David Woodhouse , Herbert Xu , "David S. Miller" , Alex Williamson , linux-pci@vger.kernel.org, linux-cxl@vger.kernel.org, linux-coco@lists.linux.dev, keyrings@vger.kernel.org, linux-crypto@vger.kernel.org, kvm@vger.kernel.org, Jonathan Cameron , linuxarm@huawei.com, David Box , Dan Williams , Dave Jiang , "Li, Ming" , Zhi Wang , Alistair Francis , Wilfred Mallawa , Tom Lendacky , Sean Christopherson , Alexander Graf Subject: Re: [PATCH 12/12] PCI/CMA: Grant guests exclusive control of authentication Message-ID: <20231009140233.GB7097@wunner.de> References: <467bff0c4bab93067b1e353e5b8a92f1de353a3f.1695921657.git.lukas@wunner.de> 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: User-Agent: Mutt/1.10.1 (2018-07-13) On Mon, Oct 09, 2023 at 09:52:00PM +1100, Alexey Kardashevskiy wrote: > On 29/9/23 03:32, Lukas Wunner wrote: > > At any given time, only a single entity in a physical system may have > > an SPDM connection to a device. That's because the GET_VERSION request > > (which begins an authentication sequence) resets "the connection and all > > context associated with that connection" (SPDM 1.3.0 margin no 158). > > > > Thus, when a device is passed through to a guest and the guest has > > authenticated it, a subsequent authentication by the host would reset > > the device's CMA-SPDM session behind the guest's back. > > > > Prevent by letting the guest claim exclusive CMA ownership of the device > > during passthrough. Refuse CMA reauthentication on the host as long. > > After passthrough has concluded, reauthenticate the device on the host. [...] > > --- a/drivers/pci/pci.h > > +++ b/drivers/pci/pci.h > > @@ -388,6 +388,7 @@ static inline bool pci_dev_is_disconnected(const struct pci_dev *dev) > > #define PCI_DEV_ADDED 0 > > #define PCI_DPC_RECOVERED 1 > > #define PCI_DPC_RECOVERING 2 > > +#define PCI_CMA_OWNED_BY_GUEST 3 > > In AMD SEV TIO, the PSP firmware creates an SPDM connection. What is the > expected way of managing such ownership, a new priv_flags bit + api for it? Right, I understand. See this ongoing discussion in reply to the cover letter: https://lore.kernel.org/all/652030759e42d_ae7e72946@dwillia2-xfh.jf.intel.com.notmuch/ In short, we need a spec amendment to negotiate between platform and OS which of the two controls the DOE instance supporting CMA-SPDM. I think the OS is free to access any Extended Capabilities in Config Space unless the platform doesn't grant it control over them through _OSC. Because the _OSC definition in the PCI Firmware Spec was not amended for CMA-SPDM, it is legal for the OS to assume control of CMA-SPDM, which is what this patch does. Thanks, Lukas