[PATCH v6 0/3] PCI/ACPI: add support for CXL _OSC

[PATCH v6 0/3] PCI/ACPI: add support for CXL _OSC

[Vishal Verma]

Changes since v5[1]:
- Collect an reviewed-by tags from Rafael, Adam, and David
- Fix a couple of missed s/CXL/extended/ in acpi_bus.h (Rafael)

Add support for using the CXL definition of _OSC where applicable, and
negotiating CXL specific support and control bits.

Patch 1 is a preliminary cleanup that replaces open-coded pointer
arithmetic to retrieve the Control DWORD with an inline helper.

Patch 2 adds the new CXL _OSC UUID, and uses it instead of the PCI UUID
when a root port is CXL enabled. It provides a fallback method for
CXL-1.1 platforms that may not implement the CXL-2.0 _OSC.

Patch 3 performs negotiation for the CXL specific _OSC support and
control bits.

I've tested these against a custom qemu[2], which adds the CXL _OSC (in
addition to other CXL support). Specifically, _OSC support is added
here[3].

[1]: https://lore.kernel.org/linux-cxl/20220406023746.2807328-1-vishal.l.verma@intel.com
[2]: https://gitlab.com/jic23/qemu/-/tree/cxl-v8-draft
[3]: https://gitlab.com/jic23/qemu/-/commit/1d67df6b6e3716c27462873f3451956f5c0673a3

Dan Williams (1):
  PCI/ACPI: Prefer CXL _OSC instead of PCIe _OSC for CXL host bridges

Vishal Verma (2):
  PCI/ACPI: add a helper for retrieving _OSC Control DWORDs
  PCI/ACPI: negotiate CXL _OSC

 include/linux/acpi.h    |  42 ++++++-
 include/acpi/acpi_bus.h |  12 +-
 drivers/acpi/bus.c      |   2 +-
 drivers/acpi/pci_root.c | 240 +++++++++++++++++++++++++++++++++++-----
 4 files changed, 262 insertions(+), 34 deletions(-)


base-commit: 05e815539f3f161585c13a9ab023341bade2c52f
-- 
2.35.1

[PATCH v6 1/3] PCI/ACPI: add a helper for retrieving _OSC Control DWORDs

[Vishal Verma]

During _OSC negotiation, when the 'Control' DWORD is needed from the
result buffer after running _OSC, a couple of places performed manual
pointer arithmetic to offset into the right spot in the raw buffer.
Add a acpi_osc_ctx_get_pci_control() helper to use the #define'd
DWORD offsets to fetch the DWORDs needed from @acpi_osc_context, and
replace the above instances of the open-coded arithmetic.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Suggested-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed by: Adam Manzanares <a.manzanares@samsung.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
---
 include/linux/acpi.h    | 13 +++++++++++++
 drivers/acpi/bus.c      |  2 +-
 drivers/acpi/pci_root.c |  2 +-
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 6274758648e3..ff4d1fdd9009 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -607,6 +607,13 @@ extern u32 osc_sb_native_usb4_control;
 #define OSC_PCI_EXPRESS_LTR_CONTROL		0x00000020
 #define OSC_PCI_EXPRESS_DPC_CONTROL		0x00000080
 
+static inline u32 acpi_osc_ctx_get_pci_control(struct acpi_osc_context *context)
+{
+	u32 *ret = context->ret.pointer;
+
+	return ret[OSC_CONTROL_DWORD];
+}
+
 #define ACPI_GSB_ACCESS_ATTRIB_QUICK		0x00000002
 #define ACPI_GSB_ACCESS_ATTRIB_SEND_RCV         0x00000004
 #define ACPI_GSB_ACCESS_ATTRIB_BYTE		0x00000006
@@ -1003,6 +1010,12 @@ static inline int acpi_register_wakeup_handler(int wake_irq,
 static inline void acpi_unregister_wakeup_handler(
 	bool (*wakeup)(void *context), void *context) { }
 
+struct acpi_osc_context;
+static inline u32 acpi_osc_ctx_get_pci_control(struct acpi_osc_context *context)
+{
+	return 0;
+}
+
 #endif	/* !CONFIG_ACPI */
 
 #ifdef CONFIG_ACPI_HOTPLUG_IOAPIC
diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index 07f604832fd6..4992e05cf429 100644
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -405,7 +405,7 @@ static void acpi_bus_osc_negotiate_usb_control(void)
 	}
 
 	osc_sb_native_usb4_control =
-		control & ((u32 *)context.ret.pointer)[OSC_CONTROL_DWORD];
+		control &  acpi_osc_ctx_get_pci_control(&context);
 
 	acpi_bus_decode_usb_osc("USB4 _OSC: OS supports", control);
 	acpi_bus_decode_usb_osc("USB4 _OSC: OS controls",
diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index b76db99cced3..40a74ff3fa02 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -185,7 +185,7 @@ static acpi_status acpi_pci_run_osc(acpi_handle handle,
 
 	status = acpi_run_osc(handle, &context);
 	if (ACPI_SUCCESS(status)) {
-		*retval = *((u32 *)(context.ret.pointer + 8));
+		*retval = acpi_osc_ctx_get_pci_control(&context);
 		kfree(context.ret.pointer);
 	}
 	return status;
-- 
2.35.1

[PATCH v6 2/3] PCI/ACPI: Prefer CXL _OSC instead of PCIe _OSC for CXL host bridges

[Vishal Verma]

From: Dan Williams <dan.j.williams@intel.com>

OB In preparation for negotiating OS control of CXL _OSC features, do the
minimal enabling to use CXL _OSC to handle the base PCIe feature
negotiation. Recall that CXL _OSC is a super-set of PCIe _OSC and the
CXL 2.0 specification mandates: "If a CXL Host Bridge device exposes CXL
_OSC, CXL aware OSPM shall evaluate CXL _OSC and not evaluate PCIe
_OSC."

Rather than pass a boolean flag alongside @root to all the helper
functions that need to consider PCIe specifics, add is_pcie() and
is_cxl() helper functions to check the flavor of @root. This also
allows for dynamic fallback to PCIe _OSC in cases where an attempt to
use CXL _OXC fails. This can happen on CXL 1.1 platforms that publish
ACPI0016 devices to indicate CXL host bridges, but do not publish the
optional CXL _OSC method. CXL _OSC is mandatory for CXL 2.0 hosts.

Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Robert Moore <robert.moore@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
---
 include/linux/acpi.h    |  4 +++
 include/acpi/acpi_bus.h |  6 ++++
 drivers/acpi/pci_root.c | 69 ++++++++++++++++++++++++++++++++---------
 3 files changed, 64 insertions(+), 15 deletions(-)

diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index ff4d1fdd9009..fc40da914315 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -550,6 +550,10 @@ struct acpi_osc_context {
 
 acpi_status acpi_run_osc(acpi_handle handle, struct acpi_osc_context *context);
 
+/* Number of _OSC capability DWORDS depends on bridge type */
+#define OSC_PCI_CAPABILITY_DWORDS		3
+#define OSC_CXL_CAPABILITY_DWORDS		5
+
 /* Indexes into _OSC Capabilities Buffer (DWORDs 2 & 3 are device-specific) */
 #define OSC_QUERY_DWORD				0	/* DWORD 1 */
 #define OSC_SUPPORT_DWORD			1	/* DWORD 2 */
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index ca88c4706f2b..9413d2389711 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -581,10 +581,16 @@ int unregister_acpi_bus_type(struct acpi_bus_type *);
 int acpi_bind_one(struct device *dev, struct acpi_device *adev);
 int acpi_unbind_one(struct device *dev);
 
+enum acpi_bridge_type {
+	ACPI_BRIDGE_TYPE_PCIE = 1,
+	ACPI_BRIDGE_TYPE_CXL,
+};
+
 struct acpi_pci_root {
 	struct acpi_device * device;
 	struct pci_bus *bus;
 	u16 segment;
+	int bridge_type;
 	struct resource secondary;	/* downstream bus range */
 
 	u32 osc_support_set;	/* _OSC state of support bits */
diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 40a74ff3fa02..b50b5de231c2 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -170,20 +170,45 @@ static void decode_osc_control(struct acpi_pci_root *root, char *msg, u32 word)
 			ARRAY_SIZE(pci_osc_control_bit));
 }
 
-static u8 pci_osc_uuid_str[] = "33DB4D5B-1FF7-401C-9657-7441C03DD766";
+static inline bool is_pcie(struct acpi_pci_root *root)
+{
+	return root->bridge_type == ACPI_BRIDGE_TYPE_PCIE;
+}
 
-static acpi_status acpi_pci_run_osc(acpi_handle handle,
+static inline bool is_cxl(struct acpi_pci_root *root)
+{
+	return root->bridge_type == ACPI_BRIDGE_TYPE_CXL;
+}
+
+static u8 pci_osc_uuid_str[] = "33DB4D5B-1FF7-401C-9657-7441C03DD766";
+static u8 cxl_osc_uuid_str[] = "68F2D50B-C469-4d8A-BD3D-941A103FD3FC";
+
+static char *to_uuid(struct acpi_pci_root *root)
+{
+	if (is_cxl(root))
+		return cxl_osc_uuid_str;
+	return pci_osc_uuid_str;
+}
+
+static int cap_length(struct acpi_pci_root *root)
+{
+	if (is_cxl(root))
+		return sizeof(u32) * OSC_CXL_CAPABILITY_DWORDS;
+	return sizeof(u32) * OSC_PCI_CAPABILITY_DWORDS;
+}
+
+static acpi_status acpi_pci_run_osc(struct acpi_pci_root *root,
 				    const u32 *capbuf, u32 *retval)
 {
 	struct acpi_osc_context context = {
-		.uuid_str = pci_osc_uuid_str,
+		.uuid_str = to_uuid(root),
 		.rev = 1,
-		.cap.length = 12,
+		.cap.length = cap_length(root),
 		.cap.pointer = (void *)capbuf,
 	};
 	acpi_status status;
 
-	status = acpi_run_osc(handle, &context);
+	status = acpi_run_osc(root->device->handle, &context);
 	if (ACPI_SUCCESS(status)) {
 		*retval = acpi_osc_ctx_get_pci_control(&context);
 		kfree(context.ret.pointer);
@@ -196,7 +221,7 @@ static acpi_status acpi_pci_query_osc(struct acpi_pci_root *root,
 					u32 *control)
 {
 	acpi_status status;
-	u32 result, capbuf[3];
+	u32 result, capbuf[OSC_CXL_CAPABILITY_DWORDS];
 
 	support |= root->osc_support_set;
 
@@ -204,10 +229,18 @@ static acpi_status acpi_pci_query_osc(struct acpi_pci_root *root,
 	capbuf[OSC_SUPPORT_DWORD] = support;
 	capbuf[OSC_CONTROL_DWORD] = *control | root->osc_control_set;
 
-	status = acpi_pci_run_osc(root->device->handle, capbuf, &result);
+retry:
+	status = acpi_pci_run_osc(root, capbuf, &result);
 	if (ACPI_SUCCESS(status)) {
 		root->osc_support_set = support;
 		*control = result;
+	} else if (is_cxl(root)) {
+		/*
+		 * CXL _OSC is optional on CXL 1.1 hosts. Fall back to PCIe _OSC
+		 * upon any failure using CXL _OSC.
+		 */
+		root->bridge_type = ACPI_BRIDGE_TYPE_PCIE;
+		goto retry;
 	}
 	return status;
 }
@@ -338,7 +371,7 @@ static acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 *mask, u32 s
 	u32 req = OSC_PCI_EXPRESS_CAPABILITY_CONTROL;
 	struct acpi_pci_root *root;
 	acpi_status status;
-	u32 ctrl, capbuf[3];
+	u32 ctrl, capbuf[OSC_CXL_CAPABILITY_DWORDS];
 
 	if (!mask)
 		return AE_BAD_PARAMETER;
@@ -375,7 +408,7 @@ static acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 *mask, u32 s
 	capbuf[OSC_QUERY_DWORD] = 0;
 	capbuf[OSC_SUPPORT_DWORD] = root->osc_support_set;
 	capbuf[OSC_CONTROL_DWORD] = ctrl;
-	status = acpi_pci_run_osc(handle, capbuf, mask);
+	status = acpi_pci_run_osc(root, capbuf, mask);
 	if (ACPI_FAILURE(status))
 		return status;
 
@@ -454,8 +487,7 @@ static bool os_control_query_checks(struct acpi_pci_root *root, u32 support)
 	return true;
 }
 
-static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm,
-				 bool is_pcie)
+static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)
 {
 	u32 support, control = 0, requested = 0;
 	acpi_status status;
@@ -506,7 +538,7 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm,
 		*no_aspm = 1;
 
 		/* _OSC is optional for PCI host bridges */
-		if ((status == AE_NOT_FOUND) && !is_pcie)
+		if (status == AE_NOT_FOUND && !is_pcie(root))
 			return;
 
 		if (control) {
@@ -529,7 +561,7 @@ static int acpi_pci_root_add(struct acpi_device *device,
 	acpi_handle handle = device->handle;
 	int no_aspm = 0;
 	bool hotadd = system_state == SYSTEM_RUNNING;
-	bool is_pcie;
+	const char *acpi_hid;
 
 	root = kzalloc(sizeof(struct acpi_pci_root), GFP_KERNEL);
 	if (!root)
@@ -587,8 +619,15 @@ static int acpi_pci_root_add(struct acpi_device *device,
 
 	root->mcfg_addr = acpi_pci_root_get_mcfg_addr(handle);
 
-	is_pcie = strcmp(acpi_device_hid(device), "PNP0A08") == 0;
-	negotiate_os_control(root, &no_aspm, is_pcie);
+	acpi_hid = acpi_device_hid(root->device);
+	if (strcmp(acpi_hid, "PNP0A08") == 0)
+		root->bridge_type = ACPI_BRIDGE_TYPE_PCIE;
+	else if (strcmp(acpi_hid, "ACPI0016") == 0)
+		root->bridge_type = ACPI_BRIDGE_TYPE_CXL;
+	else
+		dev_dbg(&device->dev, "Assuming non-PCIe host bridge\n");
+
+	negotiate_os_control(root, &no_aspm);
 
 	/*
 	 * TBD: Need PCI interface for enumeration/configuration of roots.
-- 
2.35.1

[PATCH v6 3/3] PCI/ACPI: negotiate CXL _OSC

[Vishal Verma]

Add full support for negotiating _OSC as defined in the CXL 2.0 spec, as
applicable to CXL-enabled platforms. Advertise support for the CXL
features we support - 'CXL 2.0 port/device register access', 'Protocol
Error Reporting', and 'CXL Native Hot Plug'. Request control for 'CXL
Memory Error Reporting'. The requests are dependent on CONFIG_* based
prerequisites, and prior PCI enabling, similar to how the standard PCI
_OSC bits are determined.

The CXL specification does not define any additional constraints on
the hotplug flow beyond PCIe native hotplug, so a kernel that supports
native PCIe hotplug, supports CXL hotplug. For error handling protocol
and link errors just use PCIe AER. There is nascent support for
amending AER events with CXL specific status [1], but there's
otherwise no additional OS responsibility for CXL errors beyond PCIe
AER. CXL Memory Errors behave the same as typical memory errors so
CONFIG_MEMORY_FAILURE is sufficient to indicate support to platform
firmware.

[1]: https://lore.kernel.org/linux-cxl/164740402242.3912056.8303625392871313860.stgit@dwillia2-desk3.amr.corp.intel.com/

Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Robert Moore <robert.moore@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
---
 include/linux/acpi.h    |  25 +++++-
 include/acpi/acpi_bus.h |   6 +-
 drivers/acpi/pci_root.c | 179 +++++++++++++++++++++++++++++++++++-----
 3 files changed, 188 insertions(+), 22 deletions(-)

diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index fc40da914315..ade1bf0c2f00 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -554,10 +554,12 @@ acpi_status acpi_run_osc(acpi_handle handle, struct acpi_osc_context *context);
 #define OSC_PCI_CAPABILITY_DWORDS		3
 #define OSC_CXL_CAPABILITY_DWORDS		5
 
-/* Indexes into _OSC Capabilities Buffer (DWORDs 2 & 3 are device-specific) */
+/* Indexes into _OSC Capabilities Buffer (DWORDs 2 to 5 are device-specific) */
 #define OSC_QUERY_DWORD				0	/* DWORD 1 */
 #define OSC_SUPPORT_DWORD			1	/* DWORD 2 */
 #define OSC_CONTROL_DWORD			2	/* DWORD 3 */
+#define OSC_EXT_SUPPORT_DWORD			3	/* DWORD 4 */
+#define OSC_EXT_CONTROL_DWORD			4	/* DWORD 5 */
 
 /* _OSC Capabilities DWORD 1: Query/Control and Error Returns (generic) */
 #define OSC_QUERY_ENABLE			0x00000001  /* input */
@@ -611,6 +613,15 @@ extern u32 osc_sb_native_usb4_control;
 #define OSC_PCI_EXPRESS_LTR_CONTROL		0x00000020
 #define OSC_PCI_EXPRESS_DPC_CONTROL		0x00000080
 
+/* CXL _OSC: Capabilities DWORD 4: Support Field */
+#define OSC_CXL_1_1_PORT_REG_ACCESS_SUPPORT	0x00000001
+#define OSC_CXL_2_0_PORT_DEV_REG_ACCESS_SUPPORT	0x00000002
+#define OSC_CXL_PROTOCOL_ERR_REPORTING_SUPPORT	0x00000004
+#define OSC_CXL_NATIVE_HP_SUPPORT		0x00000008
+
+/* CXL _OSC: Capabilities DWORD 5: Control Field */
+#define OSC_CXL_ERROR_REPORTING_CONTROL		0x00000001
+
 static inline u32 acpi_osc_ctx_get_pci_control(struct acpi_osc_context *context)
 {
 	u32 *ret = context->ret.pointer;
@@ -618,6 +629,13 @@ static inline u32 acpi_osc_ctx_get_pci_control(struct acpi_osc_context *context)
 	return ret[OSC_CONTROL_DWORD];
 }
 
+static inline u32 acpi_osc_ctx_get_cxl_control(struct acpi_osc_context *context)
+{
+	u32 *ret = context->ret.pointer;
+
+	return ret[OSC_EXT_CONTROL_DWORD];
+}
+
 #define ACPI_GSB_ACCESS_ATTRIB_QUICK		0x00000002
 #define ACPI_GSB_ACCESS_ATTRIB_SEND_RCV         0x00000004
 #define ACPI_GSB_ACCESS_ATTRIB_BYTE		0x00000006
@@ -1020,6 +1038,11 @@ static inline u32 acpi_osc_ctx_get_pci_control(struct acpi_osc_context *context)
 	return 0;
 }
 
+static inline u32 acpi_osc_ctx_get_cxl_control(struct acpi_osc_context *context)
+{
+	return 0;
+}
+
 #endif	/* !CONFIG_ACPI */
 
 #ifdef CONFIG_ACPI_HOTPLUG_IOAPIC
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 9413d2389711..f1d053a9cfd4 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -593,8 +593,10 @@ struct acpi_pci_root {
 	int bridge_type;
 	struct resource secondary;	/* downstream bus range */
 
-	u32 osc_support_set;	/* _OSC state of support bits */
-	u32 osc_control_set;	/* _OSC state of control bits */
+	u32 osc_support_set;		/* _OSC state of support bits */
+	u32 osc_control_set;		/* _OSC state of control bits */
+	u32 osc_ext_support_set;	/* _OSC state of extended support bits */
+	u32 osc_ext_control_set;	/* _OSC state of extended control bits */
 	phys_addr_t mcfg_addr;
 };
 
diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index b50b5de231c2..32ddeb8f58bd 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -142,6 +142,17 @@ static struct pci_osc_bit_struct pci_osc_control_bit[] = {
 	{ OSC_PCI_EXPRESS_DPC_CONTROL, "DPC" },
 };
 
+static struct pci_osc_bit_struct cxl_osc_support_bit[] = {
+	{ OSC_CXL_1_1_PORT_REG_ACCESS_SUPPORT, "CXL11PortRegAccess" },
+	{ OSC_CXL_2_0_PORT_DEV_REG_ACCESS_SUPPORT, "CXL20PortDevRegAccess" },
+	{ OSC_CXL_PROTOCOL_ERR_REPORTING_SUPPORT, "CXLProtocolErrorReporting" },
+	{ OSC_CXL_NATIVE_HP_SUPPORT, "CXLNativeHotPlug" },
+};
+
+static struct pci_osc_bit_struct cxl_osc_control_bit[] = {
+	{ OSC_CXL_ERROR_REPORTING_CONTROL, "CXLMemErrorReporting" },
+};
+
 static void decode_osc_bits(struct acpi_pci_root *root, char *msg, u32 word,
 			    struct pci_osc_bit_struct *table, int size)
 {
@@ -170,6 +181,18 @@ static void decode_osc_control(struct acpi_pci_root *root, char *msg, u32 word)
 			ARRAY_SIZE(pci_osc_control_bit));
 }
 
+static void decode_cxl_osc_support(struct acpi_pci_root *root, char *msg, u32 word)
+{
+	decode_osc_bits(root, msg, word, cxl_osc_support_bit,
+			ARRAY_SIZE(cxl_osc_support_bit));
+}
+
+static void decode_cxl_osc_control(struct acpi_pci_root *root, char *msg, u32 word)
+{
+	decode_osc_bits(root, msg, word, cxl_osc_control_bit,
+			ARRAY_SIZE(cxl_osc_control_bit));
+}
+
 static inline bool is_pcie(struct acpi_pci_root *root)
 {
 	return root->bridge_type == ACPI_BRIDGE_TYPE_PCIE;
@@ -198,7 +221,8 @@ static int cap_length(struct acpi_pci_root *root)
 }
 
 static acpi_status acpi_pci_run_osc(struct acpi_pci_root *root,
-				    const u32 *capbuf, u32 *retval)
+				    const u32 *capbuf, u32 *pci_control,
+				    u32 *cxl_control)
 {
 	struct acpi_osc_context context = {
 		.uuid_str = to_uuid(root),
@@ -210,18 +234,20 @@ static acpi_status acpi_pci_run_osc(struct acpi_pci_root *root,
 
 	status = acpi_run_osc(root->device->handle, &context);
 	if (ACPI_SUCCESS(status)) {
-		*retval = acpi_osc_ctx_get_pci_control(&context);
+		*pci_control = acpi_osc_ctx_get_pci_control(&context);
+		if (is_cxl(root))
+			*cxl_control = acpi_osc_ctx_get_cxl_control(&context);
 		kfree(context.ret.pointer);
 	}
 	return status;
 }
 
-static acpi_status acpi_pci_query_osc(struct acpi_pci_root *root,
-					u32 support,
-					u32 *control)
+static acpi_status acpi_pci_query_osc(struct acpi_pci_root *root, u32 support,
+				      u32 *control, u32 cxl_support,
+				      u32 *cxl_control)
 {
 	acpi_status status;
-	u32 result, capbuf[OSC_CXL_CAPABILITY_DWORDS];
+	u32 pci_result, cxl_result, capbuf[OSC_CXL_CAPABILITY_DWORDS];
 
 	support |= root->osc_support_set;
 
@@ -229,11 +255,21 @@ static acpi_status acpi_pci_query_osc(struct acpi_pci_root *root,
 	capbuf[OSC_SUPPORT_DWORD] = support;
 	capbuf[OSC_CONTROL_DWORD] = *control | root->osc_control_set;
 
+	if (is_cxl(root)) {
+		cxl_support |= root->osc_ext_support_set;
+		capbuf[OSC_EXT_SUPPORT_DWORD] = cxl_support;
+		capbuf[OSC_EXT_CONTROL_DWORD] = *cxl_control | root->osc_ext_control_set;
+	}
+
 retry:
-	status = acpi_pci_run_osc(root, capbuf, &result);
+	status = acpi_pci_run_osc(root, capbuf, &pci_result, &cxl_result);
 	if (ACPI_SUCCESS(status)) {
 		root->osc_support_set = support;
-		*control = result;
+		*control = pci_result;
+		if (is_cxl(root)) {
+			root->osc_ext_support_set = cxl_support;
+			*cxl_control = cxl_result;
+		}
 	} else if (is_cxl(root)) {
 		/*
 		 * CXL _OSC is optional on CXL 1.1 hosts. Fall back to PCIe _OSC
@@ -356,6 +392,8 @@ EXPORT_SYMBOL_GPL(acpi_get_pci_dev);
  * @handle: ACPI handle of a PCI root bridge (or PCIe Root Complex).
  * @mask: Mask of _OSC bits to request control of, place to store control mask.
  * @support: _OSC supported capability.
+ * @cxl_mask: Mask of CXL _OSC control bits, place to store control mask.
+ * @cxl_support: CXL _OSC supported capability.
  *
  * Run _OSC query for @mask and if that is successful, compare the returned
  * mask of control bits with @req.  If all of the @req bits are set in the
@@ -366,12 +404,14 @@ EXPORT_SYMBOL_GPL(acpi_get_pci_dev);
  * _OSC bits the BIOS has granted control of, but its contents are meaningless
  * on failure.
  **/
-static acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 *mask, u32 support)
+static acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 *mask,
+					    u32 support, u32 *cxl_mask,
+					    u32 cxl_support)
 {
 	u32 req = OSC_PCI_EXPRESS_CAPABILITY_CONTROL;
 	struct acpi_pci_root *root;
 	acpi_status status;
-	u32 ctrl, capbuf[OSC_CXL_CAPABILITY_DWORDS];
+	u32 ctrl, cxl_ctrl = 0, capbuf[OSC_CXL_CAPABILITY_DWORDS];
 
 	if (!mask)
 		return AE_BAD_PARAMETER;
@@ -383,20 +423,42 @@ static acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 *mask, u32 s
 	ctrl   = *mask;
 	*mask |= root->osc_control_set;
 
+	if (is_cxl(root)) {
+		cxl_ctrl = *cxl_mask;
+		*cxl_mask |= root->osc_ext_control_set;
+	}
+
 	/* Need to check the available controls bits before requesting them. */
 	do {
-		status = acpi_pci_query_osc(root, support, mask);
+		u32 pci_missing = 0, cxl_missing = 0;
+
+		status = acpi_pci_query_osc(root, support, mask, cxl_support,
+					    cxl_mask);
 		if (ACPI_FAILURE(status))
 			return status;
-		if (ctrl == *mask)
-			break;
-		decode_osc_control(root, "platform does not support",
-				   ctrl & ~(*mask));
+		if (is_cxl(root)) {
+			if (ctrl == *mask && cxl_ctrl == *cxl_mask)
+				break;
+			pci_missing = ctrl & ~(*mask);
+			cxl_missing = cxl_ctrl & ~(*cxl_mask);
+		} else {
+			if (ctrl == *mask)
+				break;
+			pci_missing = ctrl & ~(*mask);
+		}
+		if (pci_missing)
+			decode_osc_control(root, "platform does not support",
+					   pci_missing);
+		if (cxl_missing)
+			decode_cxl_osc_control(root, "CXL platform does not support",
+					   cxl_missing);
 		ctrl = *mask;
-	} while (*mask);
+		cxl_ctrl = *cxl_mask;
+	} while (*mask || *cxl_mask);
 
 	/* No need to request _OSC if the control was already granted. */
-	if ((root->osc_control_set & ctrl) == ctrl)
+	if ((root->osc_control_set & ctrl) == ctrl &&
+	    (root->osc_ext_control_set & cxl_ctrl) == cxl_ctrl)
 		return AE_OK;
 
 	if ((ctrl & req) != req) {
@@ -408,11 +470,17 @@ static acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 *mask, u32 s
 	capbuf[OSC_QUERY_DWORD] = 0;
 	capbuf[OSC_SUPPORT_DWORD] = root->osc_support_set;
 	capbuf[OSC_CONTROL_DWORD] = ctrl;
-	status = acpi_pci_run_osc(root, capbuf, mask);
+	if (is_cxl(root)) {
+		capbuf[OSC_EXT_SUPPORT_DWORD] = root->osc_ext_support_set;
+		capbuf[OSC_EXT_CONTROL_DWORD] = cxl_ctrl;
+	}
+
+	status = acpi_pci_run_osc(root, capbuf, mask, cxl_mask);
 	if (ACPI_FAILURE(status))
 		return status;
 
 	root->osc_control_set = *mask;
+	root->osc_ext_control_set = *cxl_mask;
 	return AE_OK;
 }
 
@@ -438,6 +506,53 @@ static u32 calculate_support(void)
 	return support;
 }
 
+/*
+ * Background on hotplug support, and making it depend on only
+ * CONFIG_HOTPLUG_PCI_PCIE vs. also considering CONFIG_MEMORY_HOTPLUG:
+ *
+ * CONFIG_ACPI_HOTPLUG_MEMORY does depend on CONFIG_MEMORY_HOTPLUG, but
+ * there is no existing _OSC for memory hotplug support. The reason is that
+ * ACPI memory hotplug requires the OS to acknowledge / coordinate with
+ * memory plug events via a scan handler. On the CXL side the equivalent
+ * would be if Linux supported the Mechanical Retention Lock [1], or
+ * otherwise had some coordination for the driver of a PCI device
+ * undergoing hotplug to be consulted on whether the hotplug should
+ * proceed or not.
+ *
+ * The concern is that if Linux says no to supporting CXL hotplug then
+ * the BIOS may say no to giving the OS hotplug control of any other PCIe
+ * device. So the question here is not whether hotplug is enabled, it's
+ * whether it is handled natively by the at all OS, and if
+ * CONFIG_HOTPLUG_PCI_PCIE is enabled then the answer is "yes".
+ *
+ * Otherwise, the plan for CXL coordinated remove, since the kernel does
+ * not support blocking hotplug, is to require the memory device to be
+ * disabled before hotplug is attempted. When CONFIG_MEMORY_HOTPLUG is
+ * disabled that step will fail and the remove attempt cancelled by the
+ * user. If that is not honored and the card is removed anyway then it
+ * does not matter if CONFIG_MEMORY_HOTPLUG is enabled or not, it will
+ * cause a crash and other badness.
+ *
+ * Therefore, just say yes to CXL hotplug and require removal to
+ * be coordinated by userspace unless and until the kernel grows better
+ * mechanisms for doing "managed" removal of devices in consultation with
+ * the driver.
+ *
+ * [1]: https://lore.kernel.org/all/20201122014203.4706-1-ashok.raj@intel.com/
+ */
+static u32 calculate_cxl_support(void)
+{
+	u32 support;
+
+	support = OSC_CXL_2_0_PORT_DEV_REG_ACCESS_SUPPORT;
+	if (pci_aer_available())
+		support |= OSC_CXL_PROTOCOL_ERR_REPORTING_SUPPORT;
+	if (IS_ENABLED(CONFIG_HOTPLUG_PCI_PCIE))
+		support |= OSC_CXL_NATIVE_HP_SUPPORT;
+
+	return support;
+}
+
 static u32 calculate_control(void)
 {
 	u32 control;
@@ -469,6 +584,16 @@ static u32 calculate_control(void)
 	return control;
 }
 
+static u32 calculate_cxl_control(void)
+{
+	u32 control = 0;
+
+	if (IS_ENABLED(CONFIG_MEMORY_FAILURE))
+		control |= OSC_CXL_ERROR_REPORTING_CONTROL;
+
+	return control;
+}
+
 static bool os_control_query_checks(struct acpi_pci_root *root, u32 support)
 {
 	struct acpi_device *device = root->device;
@@ -490,6 +615,7 @@ static bool os_control_query_checks(struct acpi_pci_root *root, u32 support)
 static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)
 {
 	u32 support, control = 0, requested = 0;
+	u32 cxl_support = 0, cxl_control = 0, cxl_requested = 0;
 	acpi_status status;
 	struct acpi_device *device = root->device;
 	acpi_handle handle = device->handle;
@@ -513,10 +639,20 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)
 	if (os_control_query_checks(root, support))
 		requested = control = calculate_control();
 
-	status = acpi_pci_osc_control_set(handle, &control, support);
+	if (is_cxl(root)) {
+		cxl_support = calculate_cxl_support();
+		decode_cxl_osc_support(root, "OS supports", cxl_support);
+		cxl_requested = cxl_control = calculate_cxl_control();
+	}
+
+	status = acpi_pci_osc_control_set(handle, &control, support,
+					  &cxl_control, cxl_support);
 	if (ACPI_SUCCESS(status)) {
 		if (control)
 			decode_osc_control(root, "OS now controls", control);
+		if (cxl_control)
+			decode_cxl_osc_control(root, "OS now controls",
+					   cxl_control);
 
 		if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_ASPM) {
 			/*
@@ -545,6 +681,11 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)
 			decode_osc_control(root, "OS requested", requested);
 			decode_osc_control(root, "platform willing to grant", control);
 		}
+		if (cxl_control) {
+			decode_cxl_osc_control(root, "OS requested", cxl_requested);
+			decode_cxl_osc_control(root, "platform willing to grant",
+					   cxl_control);
+		}
 
 		dev_info(&device->dev, "_OSC: platform retains control of PCIe features (%s)\n",
 			 acpi_format_exception(status));
-- 
2.35.1

Re: [PATCH v6 0/3] PCI/ACPI: add support for CXL _OSC

[Verma, Vishal L]

On Wed, 2022-04-13 at 01:36 -0600, Vishal Verma wrote:
> Changes since v5[1]:
> - Collect an reviewed-by tags from Rafael, Adam, and David
> - Fix a couple of missed s/CXL/extended/ in acpi_bus.h (Rafael)

Rafael, or Bjorn,

Dan has offered to take this through cxl.git. Any objections to that -
would you prefer it to go through either the PCI or ACPI trees instead?

> 
> Add support for using the CXL definition of _OSC where applicable, and
> negotiating CXL specific support and control bits.
> 
> Patch 1 is a preliminary cleanup that replaces open-coded pointer
> arithmetic to retrieve the Control DWORD with an inline helper.
> 
> Patch 2 adds the new CXL _OSC UUID, and uses it instead of the PCI UUID
> when a root port is CXL enabled. It provides a fallback method for
> CXL-1.1 platforms that may not implement the CXL-2.0 _OSC.
> 
> Patch 3 performs negotiation for the CXL specific _OSC support and
> control bits.
> 
> I've tested these against a custom qemu[2], which adds the CXL _OSC (in
> addition to other CXL support). Specifically, _OSC support is added
> here[3].
> 
> [1]: https://lore.kernel.org/linux-cxl/20220406023746.2807328-1-vishal.l.verma@intel.com
> [2]: https://gitlab.com/jic23/qemu/-/tree/cxl-v8-draft
> [3]: https://gitlab.com/jic23/qemu/-/commit/1d67df6b6e3716c27462873f3451956f5c0673a3
> 
> Dan Williams (1):
>   PCI/ACPI: Prefer CXL _OSC instead of PCIe _OSC for CXL host bridges
> 
> Vishal Verma (2):
>   PCI/ACPI: add a helper for retrieving _OSC Control DWORDs
>   PCI/ACPI: negotiate CXL _OSC
> 
>  include/linux/acpi.h    |  42 ++++++-
>  include/acpi/acpi_bus.h |  12 +-
>  drivers/acpi/bus.c      |   2 +-
>  drivers/acpi/pci_root.c | 240 +++++++++++++++++++++++++++++++++++-----
>  4 files changed, 262 insertions(+), 34 deletions(-)
> 
> 
> base-commit: 05e815539f3f161585c13a9ab023341bade2c52f

Re: [PATCH v6 0/3] PCI/ACPI: add support for CXL _OSC

[Rafael J. Wysocki]

On 4/23/2022 12:24 AM, Verma, Vishal L wrote:
> On Wed, 2022-04-13 at 01:36 -0600, Vishal Verma wrote:
>> Changes since v5[1]:
>> - Collect an reviewed-by tags from Rafael, Adam, and David
>> - Fix a couple of missed s/CXL/extended/ in acpi_bus.h (Rafael)
> Rafael, or Bjorn,
>
> Dan has offered to take this through cxl.git. Any objections to that -
> would you prefer it to go through either the PCI or ACPI trees instead?

This would be fine with me, but I can take the series too.


>> Add support for using the CXL definition of _OSC where applicable, and
>> negotiating CXL specific support and control bits.
>>
>> Patch 1 is a preliminary cleanup that replaces open-coded pointer
>> arithmetic to retrieve the Control DWORD with an inline helper.
>>
>> Patch 2 adds the new CXL _OSC UUID, and uses it instead of the PCI UUID
>> when a root port is CXL enabled. It provides a fallback method for
>> CXL-1.1 platforms that may not implement the CXL-2.0 _OSC.
>>
>> Patch 3 performs negotiation for the CXL specific _OSC support and
>> control bits.
>>
>> I've tested these against a custom qemu[2], which adds the CXL _OSC (in
>> addition to other CXL support). Specifically, _OSC support is added
>> here[3].
>>
>> [1]: https://lore.kernel.org/linux-cxl/20220406023746.2807328-1-vishal.l.verma@intel.com
>> [2]: https://gitlab.com/jic23/qemu/-/tree/cxl-v8-draft
>> [3]: https://gitlab.com/jic23/qemu/-/commit/1d67df6b6e3716c27462873f3451956f5c0673a3
>>
>> Dan Williams (1):
>>    PCI/ACPI: Prefer CXL _OSC instead of PCIe _OSC for CXL host bridges
>>
>> Vishal Verma (2):
>>    PCI/ACPI: add a helper for retrieving _OSC Control DWORDs
>>    PCI/ACPI: negotiate CXL _OSC
>>
>>   include/linux/acpi.h    |  42 ++++++-
>>   include/acpi/acpi_bus.h |  12 +-
>>   drivers/acpi/bus.c      |   2 +-
>>   drivers/acpi/pci_root.c | 240 +++++++++++++++++++++++++++++++++++-----
>>   4 files changed, 262 insertions(+), 34 deletions(-)
>>
>>
>> base-commit: 05e815539f3f161585c13a9ab023341bade2c52f

Re: [PATCH v6 0/3] PCI/ACPI: add support for CXL _OSC

[Bjorn Helgaas]

On Fri, Apr 22, 2022 at 10:24:34PM +0000, Verma, Vishal L wrote:
> On Wed, 2022-04-13 at 01:36 -0600, Vishal Verma wrote:
> > Changes since v5[1]:
> > - Collect an reviewed-by tags from Rafael, Adam, and David
> > - Fix a couple of missed s/CXL/extended/ in acpi_bus.h (Rafael)
> 
> Rafael, or Bjorn,
> 
> Dan has offered to take this through cxl.git. Any objections to that -
> would you prefer it to go through either the PCI or ACPI trees instead?

OK by me if Dan or Rafael takes it.

Re: [PATCH v6 0/3] PCI/ACPI: add support for CXL _OSC

[Dan Williams]

On Mon, Apr 25, 2022 at 11:14 AM Bjorn Helgaas <helgaas@kernel.org> wrote:
>
> On Fri, Apr 22, 2022 at 10:24:34PM +0000, Verma, Vishal L wrote:
> > On Wed, 2022-04-13 at 01:36 -0600, Vishal Verma wrote:
> > > Changes since v5[1]:
> > > - Collect an reviewed-by tags from Rafael, Adam, and David
> > > - Fix a couple of missed s/CXL/extended/ in acpi_bus.h (Rafael)
> >
> > Rafael, or Bjorn,
> >
> > Dan has offered to take this through cxl.git. Any objections to that -
> > would you prefer it to go through either the PCI or ACPI trees instead?
>
> OK by me if Dan or Rafael takes it.

Thanks Bjorn, and Rafael. It simplifies a few things if it is kept
with the other CXL changes for this merge cycle, so I'll take it
through cxl.git.

Re: [PATCH v6 0/3] PCI/ACPI: add support for CXL _OSC

[Rafael J. Wysocki]

On 4/25/2022 8:13 PM, Bjorn Helgaas wrote:
> On Fri, Apr 22, 2022 at 10:24:34PM +0000, Verma, Vishal L wrote:
>> On Wed, 2022-04-13 at 01:36 -0600, Vishal Verma wrote:
>>> Changes since v5[1]:
>>> - Collect an reviewed-by tags from Rafael, Adam, and David
>>> - Fix a couple of missed s/CXL/extended/ in acpi_bus.h (Rafael)
>> Rafael, or Bjorn,
>>
>> Dan has offered to take this through cxl.git. Any objections to that -
>> would you prefer it to go through either the PCI or ACPI trees instead?
> OK by me if Dan or Rafael takes it.

All right, so it depends on whether or not there's any pending material 
for the CXL tree that will depend on these patches.  If so, it likely is 
better to route them via CXL.