[PATCH 10/20] vfio/cxl: CXL region management
From: mhonap
Date: Wed Mar 11 2026 - 16:37:03 EST
From: Manish Honap <mhonap@xxxxxxxxxx>
Add CXL region management for future guest access.
Region Management makes use of APIs provided by CXL_CORE as below:
CREATE_REGION flow:
1. Validate request (size, decoder availability)
2. Allocate HPA via cxl_get_hpa_freespace()
3. Allocate DPA via cxl_request_dpa()
4. Create region via cxl_create_region() - commits HDM decoder!
5. Get HPA range via cxl_get_region_range()
DESTROY_REGION flow:
1. Detach decoder via cxl_decoder_detach()
2. Free DPA via cxl_dpa_free()
3. Release root decoder via cxl_put_root_decoder()
Signed-off-by: Manish Honap <mhonap@xxxxxxxxxx>
---
drivers/vfio/pci/cxl/vfio_cxl_core.c | 118 ++++++++++++++++++++++++++-
drivers/vfio/pci/cxl/vfio_cxl_priv.h | 5 ++
drivers/vfio/pci/vfio_pci_priv.h | 8 ++
3 files changed, 130 insertions(+), 1 deletion(-)
diff --git a/drivers/vfio/pci/cxl/vfio_cxl_core.c b/drivers/vfio/pci/cxl/vfio_cxl_core.c
index 2da6da1c0605..9c71f592e74e 100644
--- a/drivers/vfio/pci/cxl/vfio_cxl_core.c
+++ b/drivers/vfio/pci/cxl/vfio_cxl_core.c
@@ -126,6 +126,112 @@ static int vfio_cxl_setup_regs(struct vfio_pci_core_device *vdev)
return 0;
}
+int vfio_cxl_create_cxl_region(struct vfio_pci_core_device *vdev, resource_size_t size)
+{
+ struct vfio_pci_cxl_state *cxl = vdev->cxl;
+ resource_size_t max_size;
+ int ret;
+
+ if (cxl->precommitted)
+ return 0;
+
+ cxl->cxlrd = cxl_get_hpa_freespace(cxl->cxlmd, 1,
+ CXL_DECODER_F_RAM |
+ CXL_DECODER_F_TYPE2,
+ &max_size);
+ if (IS_ERR(cxl->cxlrd))
+ return PTR_ERR(cxl->cxlrd);
+
+ /* Insufficient HPA space */
+ if (max_size < size) {
+ cxl_put_root_decoder(cxl->cxlrd);
+ cxl->cxlrd = NULL;
+ return -ENOSPC;
+ }
+
+ cxl->cxled = cxl_request_dpa(cxl->cxlmd, CXL_PARTMODE_RAM, size);
+ if (IS_ERR(cxl->cxled)) {
+ ret = PTR_ERR(cxl->cxled);
+ goto err_free_hpa;
+ }
+
+ cxl->region = cxl_create_region(cxl->cxlrd, &cxl->cxled, 1);
+ if (IS_ERR(cxl->region)) {
+ ret = PTR_ERR(cxl->region);
+ goto err_free_dpa;
+ }
+
+ return 0;
+
+err_free_dpa:
+ cxl_dpa_free(cxl->cxled);
+err_free_hpa:
+ if (cxl->cxlrd)
+ cxl_put_root_decoder(cxl->cxlrd);
+
+ return ret;
+}
+
+void vfio_cxl_destroy_cxl_region(struct vfio_pci_core_device *vdev)
+{
+ struct vfio_pci_cxl_state *cxl = vdev->cxl;
+
+ if (!cxl->region)
+ return;
+
+ cxl_unregister_region(cxl->region);
+ cxl->region = NULL;
+
+ if (cxl->precommitted)
+ return;
+
+ cxl_dpa_free(cxl->cxled);
+ cxl_put_root_decoder(cxl->cxlrd);
+}
+
+static int vfio_cxl_create_region_helper(struct vfio_pci_core_device *vdev,
+ resource_size_t capacity)
+{
+ struct vfio_pci_cxl_state *cxl = vdev->cxl;
+ struct pci_dev *pdev = vdev->pdev;
+ int ret;
+
+ if (cxl->precommitted) {
+ cxl->cxled = cxl_get_committed_decoder(cxl->cxlmd,
+ &cxl->region);
+ if (IS_ERR(cxl->cxled))
+ return PTR_ERR(cxl->cxled);
+ } else {
+ ret = vfio_cxl_create_cxl_region(vdev, capacity);
+ if (ret)
+ return ret;
+ }
+
+ if (cxl->region) {
+ struct range range;
+
+ ret = cxl_get_region_range(cxl->region, &range);
+ if (ret)
+ goto failed;
+
+ cxl->region_hpa = range.start;
+ cxl->region_size = range_len(&range);
+
+ pci_dbg(pdev, "Precommitted decoder: HPA 0x%llx size %lu MB\n",
+ cxl->region_hpa, cxl->region_size >> 20);
+ } else {
+ pci_err(pdev, "Failed to create CXL region\n");
+ ret = -ENODEV;
+ goto failed;
+ }
+
+ return 0;
+
+failed:
+ vfio_cxl_destroy_cxl_region(vdev);
+ return ret;
+}
+
/**
* vfio_pci_cxl_detect_and_init - Detect and initialize CXL Type-2 device
* @vdev: VFIO PCI device
@@ -172,6 +278,12 @@ void vfio_pci_cxl_detect_and_init(struct vfio_pci_core_device *vdev)
pci_disable_device(pdev);
+ ret = vfio_cxl_create_region_helper(vdev, SZ_256M);
+ if (ret)
+ goto failed;
+
+ cxl->precommitted = true;
+
return;
failed:
@@ -181,6 +293,10 @@ void vfio_pci_cxl_detect_and_init(struct vfio_pci_core_device *vdev)
void vfio_pci_cxl_cleanup(struct vfio_pci_core_device *vdev)
{
- if (!vdev->cxl)
+ struct vfio_pci_cxl_state *cxl = vdev->cxl;
+
+ if (!cxl || !cxl->region)
return;
+
+ vfio_cxl_destroy_cxl_region(vdev);
}
diff --git a/drivers/vfio/pci/cxl/vfio_cxl_priv.h b/drivers/vfio/pci/cxl/vfio_cxl_priv.h
index 57fed39a80da..985680842a13 100644
--- a/drivers/vfio/pci/cxl/vfio_cxl_priv.h
+++ b/drivers/vfio/pci/cxl/vfio_cxl_priv.h
@@ -17,6 +17,10 @@ struct vfio_pci_cxl_state {
struct cxl_memdev *cxlmd;
struct cxl_root_decoder *cxlrd;
struct cxl_endpoint_decoder *cxled;
+ struct cxl_region *region;
+ resource_size_t region_hpa;
+ size_t region_size;
+ void __iomem *region_vaddr;
resource_size_t hdm_reg_offset;
size_t hdm_reg_size;
resource_size_t comp_reg_offset;
@@ -24,6 +28,7 @@ struct vfio_pci_cxl_state {
u32 hdm_count;
u16 dvsec;
u8 comp_reg_bar;
+ bool precommitted;
};
/*
diff --git a/drivers/vfio/pci/vfio_pci_priv.h b/drivers/vfio/pci/vfio_pci_priv.h
index d7df5538dcde..818d99f098bf 100644
--- a/drivers/vfio/pci/vfio_pci_priv.h
+++ b/drivers/vfio/pci/vfio_pci_priv.h
@@ -137,6 +137,9 @@ static inline void vfio_pci_dma_buf_move(struct vfio_pci_core_device *vdev,
void vfio_pci_cxl_detect_and_init(struct vfio_pci_core_device *vdev);
void vfio_pci_cxl_cleanup(struct vfio_pci_core_device *vdev);
+int vfio_cxl_create_cxl_region(struct vfio_pci_core_device *vdev,
+ resource_size_t size);
+void vfio_cxl_destroy_cxl_region(struct vfio_pci_core_device *vdev);
#else
@@ -144,6 +147,11 @@ static inline void
vfio_pci_cxl_detect_and_init(struct vfio_pci_core_device *vdev) { }
static inline void
vfio_pci_cxl_cleanup(struct vfio_pci_core_device *vdev) { }
+static inline int vfio_cxl_create_cxl_region(struct vfio_pci_core_device *vdev,
+ resource_size_t size)
+{ return 0; }
+static inline void
+vfio_cxl_destroy_cxl_region(struct vfio_pci_core_device *vdev) { }
#endif /* CONFIG_VFIO_CXL_CORE */
--
2.25.1