Re: [PATCH v7 1/2] drm/amdgpu: add debugfs for reset registers list

[Somalapuram, Amaranath]

On 2/17/2022 8:36 PM, Christian König wrote:

Am 17.02.22 um 15:29 schrieb Somalapuram Amaranath:

List of register populated for dump collection during the GPU reset.

Signed-off-by: Somalapuram Amaranath <amaranath.somalapu...@amd.com>
---
  drivers/gpu/drm/amd/amdgpu/amdgpu.h         |   4 +
  drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 112 ++++++++++++++++++++
  2 files changed, 116 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h

index b85b67a88a3d..6e35f2c4c869 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -1097,6 +1097,10 @@ struct amdgpu_device {
        struct amdgpu_reset_control     *reset_cntl;
      uint32_t ip_versions[HW_ID_MAX][HWIP_MAX_INSTANCE];
+
+    /* reset dump register */
+    uint32_t            *reset_dump_reg_list;
+    int                             num_regs;
  };

    static inline struct amdgpu_device *drm_to_adev(struct drm_device *ddev) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c

index 164d6a9e9fbb..ad807350d13e 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
@@ -1609,6 +1609,116 @@ DEFINE_DEBUGFS_ATTRIBUTE(fops_ib_preempt, NULL,
  DEFINE_DEBUGFS_ATTRIBUTE(fops_sclk_set, NULL,
              amdgpu_debugfs_sclk_set, "%llu\n");
  +static ssize_t amdgpu_reset_dump_register_list_read(struct file *f,
+                char __user *buf, size_t size, loff_t *pos)
+{

+    struct amdgpu_device *adev = (struct amdgpu_device *)file_inode(f)->i_private;

+    char reg_offset[11];
+    int i, ret, len = 0;
+
+    if (*pos)
+        return 0;
+
+    ret = down_read_killable(&adev->reset_sem);

Using the _killable() variant is a really good idea here.

+
+    if (ret)
+        return ret;
+
+    if (adev->num_regs == 0)
+        return 0;
+
+    for (i = 0; i < adev->num_regs; i++) {
+        sprintf(reg_offset, "0x%x ", adev->reset_dump_reg_list[i]);
+        ret = copy_to_user(buf + len, reg_offset, strlen(reg_offset));

Uff, I'm not 100% sure if we can do copy_to_user without dropping the lock.

then I need to use kmalloc or krealloc_array.

Regards,

S.Amarnath

+
+        if (ret)
+            return -EFAULT;

But returning here without dropping the lock is certainly incorrect.

+
+        len += strlen(reg_offset);
+    }
+
+    up_read(&adev->reset_sem);
+
+    ret = copy_to_user(buf + len, "\n", 1);
+
+    if (ret)
+        return -EFAULT;
+
+    len++;
+    *pos += len;
+
+    return len;
+}
+
+static ssize_t amdgpu_reset_dump_register_list_write(struct file *f,
+            const char __user *buf, size_t size, loff_t *pos)
+{

+    struct amdgpu_device *adev = (struct amdgpu_device *)file_inode(f)->i_private;

+    char *reg_offset, *reg, reg_temp[11];
+    uint32_t reg_list[128];
+    int ret, i = 0, len = 0;
+
+    do {
+        reg_offset = reg_temp;
+        memset(reg_offset,  0, 11);

+        ret = copy_from_user(reg_offset, buf + len, min(11, ((int)size-len)));

+
+        if (ret)
+            return -EFAULT;
+
+        if (strncmp(reg_offset, "clear", 5) == 0) {

Please completely drop the idea with the clear here, that should be unnecessary.

+
+            ret = down_read_killable(&adev->reset_sem);
+
+            if (ret)
+                return ret;
+
+            kfree(adev->reset_dump_reg_list);
+            adev->reset_dump_reg_list = NULL;
+            adev->num_regs = 0;
+
+            up_read(&adev->reset_sem);
+
+            return size;
+        }
+
+        reg = strsep(&reg_offset, " ");
+        ret = kstrtouint(reg, 16, &reg_list[i]);
+
+        if (ret)
+            return -EFAULT;
+
+        len += strlen(reg) + 1;
+        i++;
+
+    } while (len < size);
+

+    adev->reset_dump_reg_list = krealloc_array(adev->reset_dump_reg_list,

+                        i, sizeof(uint32_t), GFP_KERNEL);

Well that still doesn't looks like what we need.

Here is once more the roughly what the code should do:

unsigned int i;
uint32_t *tmp;

i = 0;
do {
    tmp = krealloc_array(tmp, i, sizeof(uint32_t), GFP_KERNEL);
    copy_from_user().....
    i++;
} while (len < size);

down_write_killable();
...

swap(adev->reset_dump_reg_list, tmp);
adev->num_regs = i;
up_write();

Regards,
Christian.

+
+    ret = down_read_killable(&adev->reset_sem);
+
+    if (ret)
+        return ret;
+
+    adev->num_regs = i;
+    memcpy(adev->reset_dump_reg_list, reg_list,
+            sizeof(uint32_t) * adev->num_regs);
+
+    up_read(&adev->reset_sem);
+
+    return size;
+}
+
+
+
+static const struct file_operations amdgpu_reset_dump_register_list = {
+    .owner = THIS_MODULE,
+    .read = amdgpu_reset_dump_register_list_read,
+    .write = amdgpu_reset_dump_register_list_write,
+    .llseek = default_llseek
+};
+
  int amdgpu_debugfs_init(struct amdgpu_device *adev)
  {
      struct dentry *root = adev_to_drm(adev)->primary->debugfs_root;

@@ -1672,6 +1782,8 @@ int amdgpu_debugfs_init(struct amdgpu_device *adev)

                  &amdgpu_debugfs_test_ib_fops);
      debugfs_create_file("amdgpu_vm_info", 0444, root, adev,
                  &amdgpu_debugfs_vm_info_fops);

+    debugfs_create_file("amdgpu_reset_dump_register_list", 0644, root, adev,

+                &amdgpu_reset_dump_register_list);
        adev->debugfs_vbios_blob.data = adev->bios;
      adev->debugfs_vbios_blob.size = adev->bios_size;