PCI/IDE: Add IDE establishment helpers

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>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Link: https://patch.msgid.link/20251031212902.2256310-8-dan.j.williams@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

2 files changed, 84 insertions, 0 deletions

diff --git a/include/linux/pci-ide.h b/include/linux/pci-ide.h
new file mode 100644
index 000000000000..e638f9429bf9
--- /dev/null
+++ b/include/linux/pci-ide.h
@@ -0,0 +1,78 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Common helpers for drivers (e.g. low-level PCI/TSM drivers) implementing the
+ * IDE key management protocol (IDE_KM) as defined by:
+ * PCIe r7.0 section 6.33 Integrity & Data Encryption (IDE)
+ *
+ * Copyright(c) 2024-2025 Intel Corporation. All rights reserved.
+ */
+
+#ifndef __PCI_IDE_H__
+#define __PCI_IDE_H__
+
+enum pci_ide_partner_select {
+	PCI_IDE_EP,
+	PCI_IDE_RP,
+	PCI_IDE_PARTNER_MAX,
+	/*
+	 * In addition to the resources in each partner port the
+	 * platform / host-bridge additionally has a Stream ID pool that
+	 * it shares across root ports. Let pci_ide_stream_alloc() use
+	 * the alloc_stream_index() helper as endpoints and root ports.
+	 */
+	PCI_IDE_HB = PCI_IDE_PARTNER_MAX,
+};
+
+/**
+ * struct pci_ide_partner - Per port pair Selective IDE Stream settings
+ * @rid_start: Partner Port Requester ID range start
+ * @rid_end: Partner Port Requester ID range end
+ * @stream_index: Selective IDE Stream Register Block selection
+ * @default_stream: Endpoint uses this stream for all upstream TLPs regardless of
+ *		    address and RID association registers
+ * @setup: flag to track whether to run pci_ide_stream_teardown() for this
+ *	   partner slot
+ * @enable: flag whether to run pci_ide_stream_disable() for this partner slot
+ */
+struct pci_ide_partner {
+	u16 rid_start;
+	u16 rid_end;
+	u8 stream_index;
+	unsigned int default_stream:1;
+	unsigned int setup:1;
+	unsigned int enable:1;
+};
+
+/**
+ * struct pci_ide - PCIe Selective IDE Stream descriptor
+ * @pdev: PCIe Endpoint in the pci_ide_partner pair
+ * @partner: per-partner settings
+ * @host_bridge_stream: allocated from host bridge @ide_stream_ida pool
+ * @stream_id: unique Stream ID (within Partner Port pairing)
+ * @name: name of the established Selective IDE Stream in sysfs
+ *
+ * Negative @stream_id values indicate "uninitialized" on the
+ * expectation that with TSM established IDE the TSM owns the stream_id
+ * allocation.
+ */
+struct pci_ide {
+	struct pci_dev *pdev;
+	struct pci_ide_partner partner[PCI_IDE_PARTNER_MAX];
+	u8 host_bridge_stream;
+	int stream_id;
+	const char *name;
+};
+
+struct pci_ide_partner *pci_ide_to_settings(struct pci_dev *pdev,
+					    struct pci_ide *ide);
+struct pci_ide *pci_ide_stream_alloc(struct pci_dev *pdev);
+void pci_ide_stream_free(struct pci_ide *ide);
+int  pci_ide_stream_register(struct pci_ide *ide);
+void pci_ide_stream_unregister(struct pci_ide *ide);
+void pci_ide_stream_setup(struct pci_dev *pdev, struct pci_ide *ide);
+void pci_ide_stream_teardown(struct pci_dev *pdev, struct pci_ide *ide);
+int pci_ide_stream_enable(struct pci_dev *pdev, struct pci_ide *ide);
+void pci_ide_stream_disable(struct pci_dev *pdev, struct pci_ide *ide);
+void pci_ide_stream_release(struct pci_ide *ide);
+DEFINE_FREE(pci_ide_stream_release, struct pci_ide *, if (_T) pci_ide_stream_release(_T))
+#endif /* __PCI_IDE_H__ */
diff --git a/include/linux/pci.h b/include/linux/pci.h
index ea94799c81b0..2c8dbae4916c 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -545,6 +545,8 @@ struct pci_dev {
 	u16		ide_cap;	/* Link Integrity & Data Encryption */
 	u8		nr_ide_mem;	/* Address association resources for streams */
 	u8		nr_link_ide;	/* Link Stream count (Selective Stream offset) */
+	u16		nr_sel_ide;	/* Selective Stream count (register block allocator) */
+	struct ida	ide_stream_ida;
 	unsigned int	ide_cfg:1;	/* Config cycles over IDE */
 	unsigned int	ide_tee_limit:1; /* Disallow T=0 traffic over IDE */
 #endif
@@ -614,6 +616,10 @@ struct pci_host_bridge {
 	int		domain_nr;
 	struct list_head windows;	/* resource_entry */
 	struct list_head dma_ranges;	/* dma ranges resource list */
+#ifdef CONFIG_PCI_IDE
+	u16 nr_ide_streams; /* Max streams possibly active in @ide_stream_ida */
+	struct ida ide_stream_ida;
+#endif
 	u8 (*swizzle_irq)(struct pci_dev *, u8 *); /* Platform IRQ swizzler */
 	int (*map_irq)(const struct pci_dev *, u8, u8);
 	void (*release_fn)(struct pci_host_bridge *);