linux-kernel - [RFC 04/14] vfio/nvgrace-gpu: Introduce functions to fetch and save EGM info

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Message-ID: <20250904040828.319452-5-ankita@nvidia.com>
Date: Thu, 4 Sep 2025 04:08:18 +0000
From: <ankita@...dia.com>
To: <ankita@...dia.com>, <jgg@...dia.com>, <alex.williamson@...hat.com>,
	<yishaih@...dia.com>, <skolothumtho@...dia.com>, <kevin.tian@...el.com>,
	<yi.l.liu@...el.com>, <zhiw@...dia.com>
CC: <aniketa@...dia.com>, <cjia@...dia.com>, <kwankhede@...dia.com>,
	<targupta@...dia.com>, <vsethi@...dia.com>, <acurrid@...dia.com>,
	<apopple@...dia.com>, <jhubbard@...dia.com>, <danw@...dia.com>,
	<anuaggarwal@...dia.com>, <mochs@...dia.com>, <kjaju@...dia.com>,
	<dnigam@...dia.com>, <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [RFC 04/14] vfio/nvgrace-gpu: Introduce functions to fetch and save EGM info

From: Ankit Agrawal <ankita@...dia.com>

The nvgrace-gpu module tracks the various EGM regions on the system.
The EGM region information - Base SPA and size - are part of the ACPI
tables. This can be fetched from the DSD table using the GPU handle.

When the GPUs are bound to the nvgrace-gpu module, it fetches the EGM
region information from the ACPI table using the GPU's pci_dev. The
EGM regions are tracked in a list and the information per region is
maintained in the nvgrace_egm_dev.

Signed-off-by: Ankit Agrawal <ankita@...dia.com>
---
 drivers/vfio/pci/nvgrace-gpu/egm_dev.c | 24 +++++++++++++++++++++++-
 drivers/vfio/pci/nvgrace-gpu/egm_dev.h |  4 +++-
 drivers/vfio/pci/nvgrace-gpu/main.c    |  8 ++++++--
 include/linux/nvgrace-egm.h            |  2 ++
 4 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/drivers/vfio/pci/nvgrace-gpu/egm_dev.c b/drivers/vfio/pci/nvgrace-gpu/egm_dev.c
index 28cfd29eda56..ca50bc1f67a0 100644
--- a/drivers/vfio/pci/nvgrace-gpu/egm_dev.c
+++ b/drivers/vfio/pci/nvgrace-gpu/egm_dev.c
@@ -17,6 +17,26 @@ int nvgrace_gpu_has_egm_property(struct pci_dev *pdev, u64 *pegmpxm)
 					pegmpxm);
 }
 
+int nvgrace_gpu_fetch_egm_property(struct pci_dev *pdev, u64 *pegmphys,
+				   u64 *pegmlength)
+{
+	int ret;
+
+	/*
+	 * The memory information is present in the system ACPI tables as DSD
+	 * properties nvidia,egm-base-pa and nvidia,egm-size.
+	 */
+	ret = device_property_read_u64(&pdev->dev, "nvidia,egm-size",
+				       pegmlength);
+	if (ret)
+		return ret;
+
+	ret = device_property_read_u64(&pdev->dev, "nvidia,egm-base-pa",
+				       pegmphys);
+
+	return ret;
+}
+
 int add_gpu(struct nvgrace_egm_dev *egm_dev, struct pci_dev *pdev)
 {
 	struct gpu_node *node;
@@ -54,7 +74,7 @@ static void nvgrace_gpu_release_aux_device(struct device *device)
 
 struct nvgrace_egm_dev *
 nvgrace_gpu_create_aux_device(struct pci_dev *pdev, const char *name,
-			      u64 egmpxm)
+			      u64 egmphys, u64 egmlength, u64 egmpxm)
 {
 	struct nvgrace_egm_dev *egm_dev;
 	int ret;
@@ -64,6 +84,8 @@ nvgrace_gpu_create_aux_device(struct pci_dev *pdev, const char *name,
 		goto create_err;
 
 	egm_dev->egmpxm = egmpxm;
+	egm_dev->egmphys = egmphys;
+	egm_dev->egmlength = egmlength;
 	INIT_LIST_HEAD(&egm_dev->gpus);
 
 	egm_dev->aux_dev.id = egmpxm;
diff --git a/drivers/vfio/pci/nvgrace-gpu/egm_dev.h b/drivers/vfio/pci/nvgrace-gpu/egm_dev.h
index 1635753c9e50..2e1612445898 100644
--- a/drivers/vfio/pci/nvgrace-gpu/egm_dev.h
+++ b/drivers/vfio/pci/nvgrace-gpu/egm_dev.h
@@ -16,6 +16,8 @@ void remove_gpu(struct nvgrace_egm_dev *egm_dev, struct pci_dev *pdev);
 
 struct nvgrace_egm_dev *
 nvgrace_gpu_create_aux_device(struct pci_dev *pdev, const char *name,
-			      u64 egmphys);
+			      u64 egmphys, u64 egmlength, u64 egmpxm);
 
+int nvgrace_gpu_fetch_egm_property(struct pci_dev *pdev, u64 *pegmphys,
+				   u64 *pegmlength);
 #endif /* EGM_DEV_H */
diff --git a/drivers/vfio/pci/nvgrace-gpu/main.c b/drivers/vfio/pci/nvgrace-gpu/main.c
index 436f0ac17332..7486a1b49275 100644
--- a/drivers/vfio/pci/nvgrace-gpu/main.c
+++ b/drivers/vfio/pci/nvgrace-gpu/main.c
@@ -67,7 +67,7 @@ static struct list_head egm_dev_list;
 static int nvgrace_gpu_create_egm_aux_device(struct pci_dev *pdev)
 {
 	struct nvgrace_egm_dev_entry *egm_entry = NULL;
-	u64 egmpxm;
+	u64 egmphys, egmlength, egmpxm;
 	int ret = 0;
 	bool is_new_region = false;
 
@@ -80,6 +80,10 @@ static int nvgrace_gpu_create_egm_aux_device(struct pci_dev *pdev)
 	if (nvgrace_gpu_has_egm_property(pdev, &egmpxm))
 		goto exit;
 
+	ret = nvgrace_gpu_fetch_egm_property(pdev, &egmphys, &egmlength);
+	if (ret)
+		goto exit;
+
 	list_for_each_entry(egm_entry, &egm_dev_list, list) {
 		/*
 		 * A system could have multiple GPUs associated with an
@@ -99,7 +103,7 @@ static int nvgrace_gpu_create_egm_aux_device(struct pci_dev *pdev)
 
 	egm_entry->egm_dev =
 		nvgrace_gpu_create_aux_device(pdev, NVGRACE_EGM_DEV_NAME,
-					      egmpxm);
+					      egmphys, egmlength, egmpxm);
 	if (!egm_entry->egm_dev) {
 		ret = -EINVAL;
 		goto free_egm_entry;
diff --git a/include/linux/nvgrace-egm.h b/include/linux/nvgrace-egm.h
index e42494a2b1a6..a66906753267 100644
--- a/include/linux/nvgrace-egm.h
+++ b/include/linux/nvgrace-egm.h
@@ -17,6 +17,8 @@ struct gpu_node {
 
 struct nvgrace_egm_dev {
 	struct auxiliary_device aux_dev;
+	phys_addr_t egmphys;
+	size_t egmlength;
 	u64 egmpxm;
 	struct list_head gpus;
 };
-- 
2.34.1