[RFC 11/13] vfio/cxl: introduce VFIO CXL device cap

Zhi Wang
2024-09-20T22:35:27Z

The userspace needs CXL device information, e.g. HDM decoder registers
offset to know when the VM updates the HDM decoder and re-build the
mapping between GPA in the virtual HDM decoder base registers and the
HPA of the CXL region created by the vfio-cxl-core when initialize the
CXL device.

To acheive this, a new VFIO CXL device cap is required to convey those
information to the usersapce.

Introduce a new VFIO CXL device cap to expose necessary information to
the userspace. Initialize the cap with the information filled when the
CXL device is being initialized. vfio-pci-core fills the CXL cap into
the caps returned to userapce when CXL is enabled.

Signed-off-by: Zhi Wang <zhiw@nvidia.com>
---
drivers/vfio/pci/vfio_cxl_core.c | 15 +++++++++++++++
drivers/vfio/pci/vfio_pci_core.c | 19 ++++++++++++++++++-
include/linux/vfio_pci_core.h | 1 +
include/uapi/linux/vfio.h | 10 ++++++++++
4 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/pci/vfio_cxl_core.c b/drivers/vfio/pci/vfio_cxl_core.c
index d8b51f8792a2..cebc444b54b7 100644
--- a/drivers/vfio/pci/vfio_cxl_core.c
+++ b/drivers/vfio/pci/vfio_cxl_core.c
@@ -367,6 +367,19 @@ static int setup_virt_comp_regs(struct vfio_pci_core_device *core_dev)
return 0;
}

+static void init_vfio_cxl_cap(struct vfio_pci_core_device *core_dev)
+{
+ struct vfio_cxl *cxl = &core_dev->cxl;
+
+ cxl->cap.header.id = VFIO_DEVICE_INFO_CAP_CXL;
+ cxl->cap.header.version = 1;
+ cxl->cap.hdm_count = cxl->hdm_count;
+ cxl->cap.hdm_reg_offset = cxl->hdm_reg_offset;
+ cxl->cap.hdm_reg_size = cxl->hdm_reg_size;
+ cxl->cap.hdm_reg_bar_index = cxl->comp_reg_bar;
+ cxl->cap.dpa_size = cxl->dpa_size;
+}
+
int vfio_cxl_core_enable(struct vfio_pci_core_device *core_dev)
{
struct vfio_cxl *cxl = &core_dev->cxl;
@@ -401,6 +414,8 @@ int vfio_cxl_core_enable(struct vfio_pci_core_device *core_dev)
if (ret)
goto err_enable_cxl_device;

+ init_vfio_cxl_cap(core_dev);
+
flags = VFIO_REGION_INFO_FLAG_READ |
VFIO_REGION_INFO_FLAG_WRITE |
VFIO_REGION_INFO_FLAG_MMAP;
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index e0f23b538858..47e65e28a42b 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -963,6 +963,15 @@ static int vfio_pci_info_atomic_cap(struct vfio_pci_core_device *vdev,
return vfio_info_add_capability(caps, &cap.header, sizeof(cap));
}

+static int vfio_pci_info_cxl_cap(struct vfio_pci_core_device *vdev,
+ struct vfio_info_cap *caps)
+{
+ struct vfio_cxl *cxl = &vdev->cxl;
+
+ return vfio_info_add_capability(caps, &cxl->cap.header,
+ sizeof(cxl->cap));
+}
+
static int vfio_pci_ioctl_get_info(struct vfio_pci_core_device *vdev,
struct vfio_device_info __user *arg)
{
@@ -984,9 +993,17 @@ static int vfio_pci_ioctl_get_info(struct vfio_pci_core_device *vdev,
if (vdev->reset_works)
info.flags |= VFIO_DEVICE_FLAGS_RESET;

- if (vdev->has_cxl)
+ if (vdev->has_cxl) {
info.flags |= VFIO_DEVICE_FLAGS_CXL;

+ ret = vfio_pci_info_cxl_cap(vdev, &caps);
+ if (ret) {
+ pci_warn(vdev->pdev,
+ "Failed to setup CXL capabilities\n");
+ return ret;
+ }
+ }
+
info.num_regions = VFIO_PCI_NUM_REGIONS + vdev->num_regions;
info.num_irqs = VFIO_PCI_NUM_IRQS;

diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
index e5646aad3eb3..d79f7a91d977 100644
--- a/include/linux/vfio_pci_core.h
+++ b/include/linux/vfio_pci_core.h
@@ -80,6 +80,7 @@ struct vfio_cxl {
struct resource ram_res;

struct vfio_cxl_region region;
+ struct vfio_device_info_cap_cxl cap;
};

struct vfio_pci_core_device {
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 0895183feaac..9a5972961280 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -257,6 +257,16 @@ struct vfio_device_info_cap_pci_atomic_comp {
__u32 reserved;
};

+#define VFIO_DEVICE_INFO_CAP_CXL 6
+struct vfio_device_info_cap_cxl {
+ struct vfio_info_cap_header header;
+ __u8 hdm_count;
+ __u8 hdm_reg_bar_index;
+ __u64 hdm_reg_size;
+ __u64 hdm_reg_offset;
+ __u64 dpa_size;
+};
+
/**
* VFIO_DEVICE_GET_REGION_INFO - _IOWR(VFIO_TYPE, VFIO_BASE + 8,
* struct vfio_region_info)
--
2.34.1