[PATCH v3 1/3] ACPI: APEI: GHES: Refactor Grace decoder helpers

Split the Grace CPER processing into a separate decode step and a
print step so the parser can be exercised by KUnit without a live
ACPI device. Introduce ghes-nvidia.h to hold shared types that the
Vera decoder added in the next commit will also reference.

Parse the Grace wire payload with __packed structs and
get_unaligned_le*() for multi-byte fields, matching the Vera
decoder style. Reject nvidia_ghes_grace_reg_pair() calls with a
non-zero register count and a NULL grace_regs pointer, and
rate-limit Grace decoder diagnostics.

Signed-off-by: Kai-Heng Feng <[email protected]>
---
v3:
 - Use __packed + get_unaligned_le*() for Grace multi-byte fields,
   including register pairs (Shuai Xue).
 - Keep __counted_by / struct_size; reject NULL grace_regs when
   number_regs != 0; document the helper contract.
 - Rate-limit Grace decoder and notify error messages.
v2:
 - No change.
---
 MAINTAINERS                     |   2 +-
 drivers/acpi/apei/ghes-nvidia.c | 160 ++++++++++++++++++++++----------
 drivers/acpi/apei/ghes-nvidia.h |  50 ++++++++++
 3 files changed, 160 insertions(+), 52 deletions(-)
 create mode 100644 drivers/acpi/apei/ghes-nvidia.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 5114e6db7307..aa9c2ae58ac5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -19348,7 +19348,7 @@ NVIDIA GHES VENDOR CPER RECORD HANDLER
 M:	Kai-Heng Feng <[email protected]>
 L:	[email protected]
 S:	Maintained
-F:	drivers/acpi/apei/ghes-nvidia.c
+F:	drivers/acpi/apei/ghes-nvidia*
 
 NVIDIA VRS RTC DRIVER
 M:	Shubhi Garg <[email protected]>
diff --git a/drivers/acpi/apei/ghes-nvidia.c b/drivers/acpi/apei/ghes-nvidia.c
index 597275d81de8..e7cc912344fd 100644
--- a/drivers/acpi/apei/ghes-nvidia.c
+++ b/drivers/acpi/apei/ghes-nvidia.c
@@ -9,13 +9,18 @@
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/types.h>
+#include <linux/unaligned.h>
 #include <linux/uuid.h>
 #include <acpi/ghes.h>
 
-static const guid_t nvidia_sec_guid =
+#include <kunit/visibility.h>
+#include "ghes-nvidia.h"
+
+static const guid_t nvidia_grace_sec_guid =
 	GUID_INIT(0x6d5244f2, 0x2712, 0x11ec,
 		  0xbe, 0xa7, 0xcb, 0x3f, 0xdb, 0x95, 0xc7, 0x86);
 
+/* Grace CPER section wire layout (header without flexible register array). */
 struct cper_sec_nvidia {
 	char	signature[16];
 	__le16	error_type;
@@ -25,84 +30,137 @@ struct cper_sec_nvidia {
 	u8	number_regs;
 	u8	reserved;
 	__le64	instance_base;
-	struct {
-		__le64	addr;
-		__le64	val;
-	} regs[] __counted_by(number_regs);
-};
+	struct nvidia_ghes_grace_reg regs[] __counted_by(number_regs);
+} __packed;
+
+static_assert(sizeof(struct cper_sec_nvidia) == 32);
 
 struct nvidia_ghes_private {
 	struct notifier_block	nb;
 	struct device		*dev;
 };
 
-static void nvidia_ghes_print_error(struct device *dev,
-				    const struct cper_sec_nvidia *nvidia_err,
-				    size_t error_data_length, bool fatal)
+VISIBLE_IF_KUNIT
+int nvidia_ghes_decode_grace(struct device *dev, const void *buf,
+			     size_t len,
+			     struct nvidia_ghes_decoded *decoded)
 {
-	const char *level = fatal ? KERN_ERR : KERN_INFO;
+	const struct cper_sec_nvidia *nvidia_err = buf;
 	size_t min_size;
+	u8 number_regs;
+
+	if (!buf || !decoded)
+		return -EINVAL;
+	if (len < sizeof(*nvidia_err)) {
+		if (dev)
+			dev_err_ratelimited(dev, "Section too small (%zu < %zu)\n",
+					    len, sizeof(*nvidia_err));
+		return -ENODATA;
+	}
 
-	dev_printk(level, dev, "signature: %.16s\n", nvidia_err->signature);
-	dev_printk(level, dev, "error_type: %u\n", le16_to_cpu(nvidia_err->error_type));
-	dev_printk(level, dev, "error_instance: %u\n", le16_to_cpu(nvidia_err->error_instance));
-	dev_printk(level, dev, "severity: %u\n", nvidia_err->severity);
-	dev_printk(level, dev, "socket: %u\n", nvidia_err->socket);
-	dev_printk(level, dev, "number_regs: %u\n", nvidia_err->number_regs);
-	dev_printk(level, dev, "instance_base: 0x%016llx\n",
-		   le64_to_cpu(nvidia_err->instance_base));
-
-	if (nvidia_err->number_regs == 0)
-		return;
-
-	/*
-	 * Validate that all registers fit within error_data_length.
-	 * Each register pair is two little-endian u64s.
-	 */
-	min_size = struct_size(nvidia_err, regs, nvidia_err->number_regs);
-	if (error_data_length < min_size) {
-		dev_err(dev, "Invalid number_regs %u (section size %zu, need %zu)\n",
-			nvidia_err->number_regs, error_data_length, min_size);
-		return;
+	number_regs = nvidia_err->number_regs;
+	min_size = struct_size(nvidia_err, regs, number_regs);
+	if (len < min_size) {
+		if (dev)
+			dev_err_ratelimited(dev,
+					    "Invalid number_regs %u (section size %zu, need %zu)\n",
+					    number_regs, len, min_size);
+		return -ENODATA;
 	}
 
-	for (int i = 0; i < nvidia_err->number_regs; i++)
+	memset(decoded, 0, sizeof(*decoded));
+	decoded->format = NVIDIA_GHES_FORMAT_GRACE;
+	memcpy(decoded->signature, nvidia_err->signature, sizeof(nvidia_err->signature));
+	decoded->signature[sizeof(nvidia_err->signature)] = '\0';
+	decoded->error_type = get_unaligned_le16(&nvidia_err->error_type);
+	decoded->error_instance = get_unaligned_le16(&nvidia_err->error_instance);
+	decoded->severity = nvidia_err->severity;
+	decoded->socket = nvidia_err->socket;
+	decoded->number_regs = number_regs;
+	decoded->instance_base = get_unaligned_le64(&nvidia_err->instance_base);
+	if (number_regs)
+		decoded->grace_regs = nvidia_err->regs;
+
+	return 0;
+}
+EXPORT_SYMBOL_IF_KUNIT(nvidia_ghes_decode_grace);
+
+VISIBLE_IF_KUNIT
+int nvidia_ghes_grace_reg_pair(const struct nvidia_ghes_decoded *decoded,
+			       unsigned int index, u64 *addr, u64 *val)
+{
+	const struct nvidia_ghes_grace_reg *regs;
+
+	if (!decoded || decoded->format != NVIDIA_GHES_FORMAT_GRACE || !addr || !val)
+		return -EINVAL;
+	if (decoded->number_regs && !decoded->grace_regs)
+		return -EINVAL;
+	if (index >= decoded->number_regs)
+		return -ERANGE;
+
+	regs = decoded->grace_regs;
+	*addr = get_unaligned_le64(&regs[index].addr);
+	*val = get_unaligned_le64(&regs[index].val);
+
+	return 0;
+}
+EXPORT_SYMBOL_IF_KUNIT(nvidia_ghes_grace_reg_pair);
+
+static void nvidia_ghes_print_grace(struct device *dev,
+				    const struct nvidia_ghes_decoded *decoded,
+				    bool fatal)
+{
+	const char *level = fatal ? KERN_ERR : KERN_INFO;
+	u64 addr, val;
+
+	dev_printk(level, dev, "signature: %s\n", decoded->signature);
+	dev_printk(level, dev, "error_type: %u\n", decoded->error_type);
+	dev_printk(level, dev, "error_instance: %u\n", decoded->error_instance);
+	dev_printk(level, dev, "severity: %u\n", decoded->severity);
+	dev_printk(level, dev, "socket: %u\n", decoded->socket);
+	dev_printk(level, dev, "number_regs: %u\n", decoded->number_regs);
+	dev_printk(level, dev, "instance_base: 0x%016llx\n", decoded->instance_base);
+
+	for (int i = 0; i < decoded->number_regs; i++) {
+		if (nvidia_ghes_grace_reg_pair(decoded, i, &addr, &val))
+			break;
 		dev_printk(level, dev, "register[%d]: address=0x%016llx value=0x%016llx\n",
-			   i, le64_to_cpu(nvidia_err->regs[i].addr),
-			   le64_to_cpu(nvidia_err->regs[i].val));
+			   i, addr, val);
+	}
 }
 
 static int nvidia_ghes_notify(struct notifier_block *nb,
 			      unsigned long event, void *data)
 {
 	struct acpi_hest_generic_data *gdata = data;
+	struct nvidia_ghes_decoded decoded = {};
 	struct nvidia_ghes_private *priv;
-	const struct cper_sec_nvidia *nvidia_err;
+	const void *payload;
 	guid_t sec_guid;
+	u32 len;
+	int ret;
+	bool fatal;
 
 	import_guid(&sec_guid, gdata->section_type);
-	if (!guid_equal(&sec_guid, &nvidia_sec_guid))
+	if (!guid_equal(&sec_guid, &nvidia_grace_sec_guid))
 		return NOTIFY_DONE;
 
 	priv = container_of(nb, struct nvidia_ghes_private, nb);
-
-	if (acpi_hest_get_error_length(gdata) < sizeof(*nvidia_err)) {
-		dev_err(priv->dev, "Section too small (%d < %zu)\n",
-			acpi_hest_get_error_length(gdata), sizeof(*nvidia_err));
+	len = acpi_hest_get_error_length(gdata);
+	payload = acpi_hest_get_payload(gdata);
+	fatal = event >= GHES_SEV_RECOVERABLE;
+
+	ret = nvidia_ghes_decode_grace(priv->dev, payload, len, &decoded);
+	if (ret) {
+		dev_err_ratelimited(priv->dev,
+				    "Malformed NVIDIA CPER section, error_data_length: %u, ret: %d\n",
+				    len, ret);
 		return NOTIFY_OK;
 	}
 
-	nvidia_err = acpi_hest_get_payload(gdata);
-
-	if (event >= GHES_SEV_RECOVERABLE)
-		dev_err(priv->dev, "NVIDIA CPER section, error_data_length: %u\n",
-			acpi_hest_get_error_length(gdata));
-	else
-		dev_info(priv->dev, "NVIDIA CPER section, error_data_length: %u\n",
-			 acpi_hest_get_error_length(gdata));
-
-	nvidia_ghes_print_error(priv->dev, nvidia_err, acpi_hest_get_error_length(gdata),
-				event >= GHES_SEV_RECOVERABLE);
+	dev_printk(fatal ? KERN_ERR : KERN_INFO, priv->dev,
+		   "NVIDIA CPER section, error_data_length: %u\n", len);
+	nvidia_ghes_print_grace(priv->dev, &decoded, fatal);
 
 	return NOTIFY_OK;
 }
diff --git a/drivers/acpi/apei/ghes-nvidia.h b/drivers/acpi/apei/ghes-nvidia.h
new file mode 100644
index 000000000000..965abe3d5c49
--- /dev/null
+++ b/drivers/acpi/apei/ghes-nvidia.h
@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef GHES_NVIDIA_H
+#define GHES_NVIDIA_H
+
+#include <linux/build_bug.h>
+#include <linux/types.h>
+#include <kunit/visibility.h>
+
+struct device;
+
+enum nvidia_ghes_format {
+	NVIDIA_GHES_FORMAT_UNKNOWN,
+	NVIDIA_GHES_FORMAT_GRACE,
+};
+
+struct nvidia_ghes_grace_reg {
+	__le64 addr;
+	__le64 val;
+} __packed;
+
+struct nvidia_ghes_decoded {
+	enum nvidia_ghes_format format;
+	char signature[17];
+	u16 error_type;
+	u16 error_instance;
+	u8 severity;
+	u8 socket;
+	u8 number_regs;
+	u64 instance_base;
+	const struct nvidia_ghes_grace_reg *grace_regs;
+};
+
+/**
+ * nvidia_ghes_grace_reg_pair() - Read one Grace register address/value pair
+ * @decoded: Decoded Grace section; format must be NVIDIA_GHES_FORMAT_GRACE
+ * @index: Register index in [0, number_regs)
+ * @addr: Output register address
+ * @val: Output register value
+ *
+ * When number_regs is non-zero, decoded->grace_regs must be non-NULL.
+ * Returns -EINVAL for bad arguments / missing grace_regs, -ERANGE for
+ * index >= number_regs, and 0 on success.
+ */
+VISIBLE_IF_KUNIT int nvidia_ghes_decode_grace(struct device *dev, const void *buf,
+					      size_t len,
+					      struct nvidia_ghes_decoded *decoded);
+VISIBLE_IF_KUNIT int nvidia_ghes_grace_reg_pair(const struct nvidia_ghes_decoded *decoded,
+						unsigned int index, u64 *addr, u64 *val);
+
+#endif
-- 
2.50.1 (Apple Git-155)