Re: [PATCH 3/7] libcxl: Add poison injection support

Dave Jiang
2026-01-09T18:03:21Z

On 1/9/26 9:07 AM, Ben Cheatham wrote:
> Add a library API for clearing and injecting poison into a CXL memory
> device through the CXL debugfs.
>
> This API will be used by the 'cxl-inject-error' and 'cxl-clear-error'
> commands in later commits.
>
> Signed-off-by: Ben Cheatham <Benjamin.Cheatham@amd.com>
> ---
> cxl/lib/libcxl.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++
> cxl/lib/libcxl.sym | 3 ++
> cxl/libcxl.h | 3 ++
> 3 files changed, 89 insertions(+)
>
> diff --git a/cxl/lib/libcxl.c b/cxl/lib/libcxl.c
> index 27ff037..deebf7f 100644
> --- a/cxl/lib/libcxl.c
> +++ b/cxl/lib/libcxl.c
> @@ -5046,3 +5046,86 @@ CXL_EXPORT struct cxl_cmd *cxl_cmd_new_set_alert_config(struct cxl_memdev *memde
> {
> return cxl_cmd_new_generic(memdev, CXL_MEM_COMMAND_ID_SET_ALERT_CONFIG);
> }
> +
> +CXL_EXPORT bool cxl_memdev_has_poison_injection(struct cxl_memdev *memdev)
> +{
> + struct cxl_ctx *ctx = memdev->ctx;
> + size_t path_len, len;
> + bool exists = true;
> + char *path;
> + int rc;
> +
> + if (!ctx->cxl_debugfs)
> + return false;
> +
> + path_len = strlen(ctx->cxl_debugfs) + 100;

Same comment about PATH_MAX.

> + path = calloc(path_len, sizeof(char));
> + if (!path)
> + return false;
> +
> + len = snprintf(path, path_len, "%s/%s/inject_poison", ctx->cxl_debugfs,
> + cxl_memdev_get_devname(memdev));
> + if (len >= path_len) {
> + err(ctx, "%s: buffer too small\n",
> + cxl_memdev_get_devname(memdev));
> + free(path);
> + return false;

I think I saw in an earlier patch that you were using goto to filter error exit point. So may as well make it consistent and do it here as well.

> + }
> +
> + rc = access(path, F_OK);
> + if (rc)
> + exists = false;
> +
> + free(path);
> + return exists;
> +}
> +
> +static int cxl_memdev_poison_action(struct cxl_memdev *memdev, size_t dpa,
> + bool clear)
> +{
> + struct cxl_ctx *ctx = memdev->ctx;
> + size_t path_len, len;
> + char addr[32];
> + char *path;
> + int rc;
> +
> + if (!ctx->cxl_debugfs)
> + return -ENOENT;
> +
> + path_len = strlen(ctx->cxl_debugfs) + 100;

same comment about path len

> + path = calloc(path_len, sizeof(char));
> + if (!path)
> + return -ENOMEM;
> +
> + len = snprintf(path, path_len, "%s/%s/%s", ctx->cxl_debugfs,
> + cxl_memdev_get_devname(memdev),
> + clear ? "clear_poison" : "inject_poison");
> + if (len >= path_len) {
> + err(ctx, "%s: buffer too small\n",
> + cxl_memdev_get_devname(memdev));
> + free(path);
> + return -ENOMEM;

same comment about error paths

DJ

> + }
> +
> + len = snprintf(addr, sizeof(addr), "0x%lx\n", dpa);
> + if (len >= sizeof(addr)) {
> + err(ctx, "%s: buffer too small\n",
> + cxl_memdev_get_devname(memdev));
> + free(path);
> + return -ENOMEM;
> + }
> +
> + rc = sysfs_write_attr(ctx, path, addr);
> + free(path);
> + return rc;
> +}
> +
> +CXL_EXPORT int cxl_memdev_inject_poison(struct cxl_memdev *memdev, size_t addr)
> +{
> + return cxl_memdev_poison_action(memdev, addr, false);
> +}
> +
> +CXL_EXPORT int cxl_memdev_clear_poison(struct cxl_memdev *memdev, size_t addr)
> +{
> + return cxl_memdev_poison_action(memdev, addr, true);
> +}
> diff --git a/cxl/lib/libcxl.sym b/cxl/lib/libcxl.sym
> index c683b83..c636edb 100644
> --- a/cxl/lib/libcxl.sym
> +++ b/cxl/lib/libcxl.sym
> @@ -309,4 +309,7 @@ global:
> cxl_protocol_error_get_num;
> cxl_protocol_error_get_str;
> cxl_dport_protocol_error_inject;
> + cxl_memdev_has_poison_injection;
> + cxl_memdev_inject_poison;
> + cxl_memdev_clear_poison;
> } LIBCXL_10;
> diff --git a/cxl/libcxl.h b/cxl/libcxl.h
> index faef62e..4d035f0 100644
> --- a/cxl/libcxl.h
> +++ b/cxl/libcxl.h
> @@ -105,6 +105,9 @@ int cxl_memdev_read_label(struct cxl_memdev *memdev, void *buf, size_t length,
> size_t offset);
> int cxl_memdev_write_label(struct cxl_memdev *memdev, void *buf, size_t length,
> size_t offset);
> +bool cxl_memdev_has_poison_injection(struct cxl_memdev *memdev);
> +int cxl_memdev_inject_poison(struct cxl_memdev *memdev, size_t dpa);
> +int cxl_memdev_clear_poison(struct cxl_memdev *memdev, size_t dpa);
> struct cxl_cmd *cxl_cmd_new_get_fw_info(struct cxl_memdev *memdev);
> unsigned int cxl_cmd_fw_info_get_num_slots(struct cxl_cmd *cmd);
> unsigned int cxl_cmd_fw_info_get_active_slot(struct cxl_cmd *cmd);