drm/amd/ras: chunk UNIRAS CPER debugfs reads

Legacy CPER ring readers can issue one debugfs read with a buffer larger
than the UNIRAS RAS command payload limit. Passing that full size to
GET_CPER_RECORD makes the command reject the request, so userspace may
only see the ring prefix and treat the CPER stream as empty.

Commit 3c88fb7aa57d ("drm/amd/ras: bound CPER record fetch buffer
size") intentionally bounds CPER record fetch allocation by the command
buffer size. Keep the debugfs ABI as a single contiguous ring read by
splitting the internal GET_CPER_RECORD requests into
RAS_CMD_MAX_CPER_BUF_SZ chunks.

Accumulate the copied payload and update the legacy header write pointers
from the total bytes returned to userspace.

Signed-off-by: Xiang Liu <xiang.liu@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
index 7e496607de1ad11e18e7eb5aec18accc301b8e87..b97fa35bac2325a6b91763d74bbea032d32b1bfa 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c
@@ -501,6 +501,8 @@ static ssize_t amdgpu_ras_cper_debugfs_read(struct file *f, char __user *buf,
        u32 total_cper_num;
        u64 start_cper_id;
        u64 cper_offset;
+       size_t chunk_size;
+       size_t total_data_size = 0;
        bool read_header;
        int r;
 
@@ -550,30 +552,45 @@ static ssize_t amdgpu_ras_cper_debugfs_read(struct file *f, char __user *buf,
        if (!data_size)
                return 0;
 
-       record_req->buf_ptr = (u64)(uintptr_t)data_buf;
-       record_req->buf_size = data_size;
-       record_req->cper_start_id = start_cper_id + cper_offset;
-       record_req->cper_num = total_cper_num - cper_offset;
-       r = amdgpu_ras_mgr_handle_ras_cmd(ring->adev,
-                                         RAS_CMD__GET_CPER_RECORD,
-                                         record_req, sizeof(struct ras_cmd_cper_record_req),
-                                         record_rsp, sizeof(struct ras_cmd_cper_record_rsp));
-       if (r)
-               return r;
-       if (record_rsp->real_data_size > data_size)
-               return -EIO;
+       while (data_size && cper_offset < total_cper_num) {
+               memset(record_req, 0, sizeof(*record_req));
+               memset(record_rsp, 0, sizeof(*record_rsp));
+               chunk_size = min_t(size_t, data_size, RAS_CMD_MAX_CPER_BUF_SZ);
+
+               record_req->buf_ptr = (u64)(uintptr_t)data_buf;
+               record_req->buf_size = chunk_size;
+               record_req->cper_start_id = start_cper_id + cper_offset;
+               record_req->cper_num = total_cper_num - cper_offset;
+               r = amdgpu_ras_mgr_handle_ras_cmd(ring->adev,
+                                                 RAS_CMD__GET_CPER_RECORD,
+                                                 record_req,
+                                                 sizeof(struct ras_cmd_cper_record_req),
+                                                 record_rsp,
+                                                 sizeof(struct ras_cmd_cper_record_rsp));
+               if (r)
+                       return r;
+
+               if (!record_rsp->real_data_size || !record_rsp->real_cper_num)
+                       break;
+               if (record_rsp->real_data_size > data_size)
+                       return -EIO;
+
+               data_buf += record_rsp->real_data_size;
+               data_size -= record_rsp->real_data_size;
+               total_data_size += record_rsp->real_data_size;
+               cper_offset += record_rsp->real_cper_num;
+       }
 
        if (read_header) {
-               ring_header[1] = record_rsp->real_data_size >> 2;
+               ring_header[1] = total_data_size >> 2;
                ring_header[2] = ring_header[1];
 
                if (copy_to_user(buf, ring_header, ring_header_size))
                        return -EFAULT;
        }
 
-       r = read_header ? record_rsp->real_data_size + ring_header_size :
-                               record_rsp->real_data_size;
-       *offset = cper_offset + record_rsp->real_cper_num + 1;
+       r = read_header ? total_data_size + ring_header_size : total_data_size;
+       *offset = cper_offset + 1;
 
        return r;
 }