Re: [PATCH v8 7/9] PCI/IDE: Add IDE establishment helpers

[Jonathan Cameron <jonathan.cameron@huawei.com>]

On Fri, 31 Oct 2025 14:28:59 -0700
Dan Williams <dan.j.williams@intel.com> wrote:

> There are two components to establishing an encrypted link, provisioning
> the stream in Partner Port config-space, and programming the keys into
> the link layer via IDE_KM (IDE Key Management). This new library,
> drivers/pci/ide.c, enables the former. IDE_KM, via a TSM low-level
> driver, is saved for later.
> 
> With the platform TSM implementations of SEV-TIO and TDX Connect in mind
> this library abstracts small differences in those implementations. For
> example, TDX Connect handles Root Port register setup while SEV-TIO
> expects System Software to update the Root Port registers. This is the
> rationale for fine-grained 'setup' + 'enable' verbs.
> 
> The other design detail for TSM-coordinated IDE establishment is that
> the TSM may manage allocation of Stream IDs, this is why the Stream ID
> value is passed in to pci_ide_stream_setup().
> 
> The flow is:
> 
> pci_ide_stream_alloc():
>     Allocate a Selective IDE Stream Register Block in each Partner Port
>     (Endpoint + Root Port), and reserve a host bridge / platform stream
>     slot. Gather Partner Port specific stream settings like Requester ID.
> 
> pci_ide_stream_register():
>     Publish the stream in sysfs after allocating a Stream ID. In the TSM
>     case the TSM allocates the Stream ID for the Partner Port pair.
> 
> pci_ide_stream_setup():
>     Program the stream settings to a Partner Port. Caller is responsible
>     for optionally calling this for the Root Port as well if the TSM
>     implementation requires it.
> 
> pci_ide_stream_enable():
>     Enable the stream after IDE_KM.
> 
> In support of system administrators auditing where platform, Root Port,
> and Endpoint IDE stream resources are being spent, the allocated stream
> is reflected as a symlink from the host bridge to the endpoint with the
> name:
> 
>     stream%d.%d.%d
> 
> Where the tuple of integers reflects the allocated platform, Root Port,
> and Endpoint stream index (Selective IDE Stream Register Block) values.
> 
> Thanks to Wu Hao for a draft implementation of this infrastructure.
> 
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: Lukas Wunner <lukas@wunner.de>
> Cc: Samuel Ortiz <sameo@rivosinc.com>
> Co-developed-by: Alexey Kardashevskiy <aik@amd.com>
> Signed-off-by: Alexey Kardashevskiy <aik@amd.com>
> Co-developed-by: Xu Yilun <yilun.xu@linux.intel.com>
> Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>
> Acked-by: Bjorn Helgaas <bhelgaas@google.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>