Re: [RFC PATCH 5/5] PCI/TSM: Authenticate devices via platform TSM

From: Dan Williams <dan.j.williams@intel.com>
To: Alexey Kardashevskiy <aik@amd.com>,
	Dan Williams <dan.j.williams@intel.com>,
	<linux-coco@lists.linux.dev>
Cc: Wu Hao <hao.wu@intel.com>, Yilun Xu <yilun.xu@intel.com>,
	Lukas Wunner <lukas@wunner.de>, Samuel Ortiz <sameo@rivosinc.com>,
	Bjorn Helgaas <bhelgaas@google.com>, <linux-pci@vger.kernel.org>,
	<gregkh@linuxfoundation.org>
Subject: Re: [RFC PATCH 5/5] PCI/TSM: Authenticate devices via platform TSM
Date: Mon, 26 Feb 2024 21:59:58 -0800	[thread overview]
Message-ID: <65dd7a5e78ded_1138c7294f@dwillia2-xfh.jf.intel.com.notmuch> (raw)
In-Reply-To: <79921a75-6d90-4d7c-9aac-5df4430cf985@amd.com>

Alexey Kardashevskiy wrote:
[..]
> > diff --git a/drivers/pci/cma.c b/drivers/pci/cma.c
> > index be7d2bb21b4c..5a69e9919589 100644
> > --- a/drivers/pci/cma.c
> > +++ b/drivers/pci/cma.c
> > @@ -39,6 +39,9 @@ static ssize_t authenticated_store(struct device *dev,
> >   	if (!sysfs_streq(buf, "native"))
> >   		return -EINVAL;
> >   
> > +	if (pci_tsm_authenticated(pdev))
> > +		return -EBUSY;
> > +
> >   	rc = pci_cma_reauthenticate(pdev);
> >   	if (rc)
> >   		return rc;
> 
> btw is this "native" CMA expected to migrate to tsm_pci_ops? Thanks,

No, CMA is independent from TSM enabling. So you have the option to only
ever authenticate devices via kernel-native CMA, and ignore TEE I/O and
the platform TSM completely. Or, once CMA authentication succeeds then
the kernel additionally allows transitioning the device to be TSM
authenticated / connected.

This keeps the Linux device-attestation ecosystem healthy, standards
compliant devices with managed certificate distribution.