[PATCH v6 1/2] drm/amdgpu: add debugfs for reset registers list
Somalapuram, Amaranath
asomalap at amd.com
Wed Feb 16 13:11:19 UTC 2022
On 2/16/2022 3:41 PM, Christian König wrote:
> Am 16.02.22 um 10:49 schrieb Somalapuram Amaranath:
>> List of register populated for dump collection during the GPU reset.
>>
>> Signed-off-by: Somalapuram Amaranath <Amaranath.Somalapuram at amd.com>
>> ---
>> drivers/gpu/drm/amd/amdgpu/amdgpu.h | 5 ++
>> drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 95 +++++++++++++++++++++
>> 2 files changed, 100 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>> index b85b67a88a3d..57965316873b 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>> @@ -1097,6 +1097,11 @@ 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 n_regs;
>> + struct mutex reset_dump_mutex;
>
> I think we should rather use the reset lock for this instead of
> introducing just another mutex.
>
>> };
>> 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..faf985c7cb93 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
>> @@ -1609,6 +1609,98 @@ 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, r, len = 0;
>> +
>> + if (*pos)
>> + return 0;
>> +
>> + if (adev->n_regs == 0)
>> + return 0;
>> +
>> + for (i = 0; i < adev->n_regs; i++) {
>> + sprintf(reg_offset, "0x%x ", adev->reset_dump_reg_list[i]);
>> + r = copy_to_user(buf + len, reg_offset, strlen(reg_offset));
>> +
>> + if (r)
>> + return -EFAULT;
>> +
>> + len += strlen(reg_offset);
>> + }
>
> You need to hold the lock protecting adev->reset_dump_reg_list and
> adev->n_regs while accessing those.
>
> (BTW: num_regs instead of n_regs would match more what we use
> elsewhere, but is not a must have).
>
This is read function for user and returns only list of reg offsets, I
did not understand correctly !
>> +
>> + r = copy_to_user(buf + len, "\n", 1);
>> +
>> + if (r)
>> + 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];
>> + static int alloc_count;
>> + 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)
>> + goto failed;
>> +
>> + reg = strsep(®_offset, " ");
>> +
>> + if (alloc_count <= i) {
>
>> + adev->reset_dump_reg_list = krealloc_array(
>> + adev->reset_dump_reg_list, 1,
>> + sizeof(uint32_t), GFP_KERNEL);
>> + alloc_count++;
>> + }
>> +
>> + ret = kstrtouint(reg, 16, &adev->reset_dump_reg_list[i]);
>
> This here is modifying adev->reset_dump_reg_list as well and so must
> be protected by a lock as well.
>
> The tricky part is that we can't allocate memory while holding this
> lock (because we need it during reset as well).
>
> One solution for this is to read the register list into a local array
> first and when that's done swap the local array with the one in
> adev->reset_dump_reg_list while holding the lock.
>
> Regards,
> Christian.
>
There are 2 situations:
1st time creating list n_regs will be 0 and trace event will not be
triggered
2nd time while updating list n_regs is already set and
adev->reset_dump_reg_list will have some offsets address (hypothetically
speaking *during reset + update* read values from RREG32 will mix up of
old list and new list)
its only critical when its freed and n_regs is not 0
Regards,
S.Amarnath
>> +
>> + if (ret)
>> + goto failed;
>> +
>> + len += strlen(reg) + 1;
>> + i++;
>> +
>> + } while (len < size);
>> +
>> + adev->n_regs = i;
>> +
>> + return size;
>> +
>> +failed:
>> + mutex_lock(&adev->reset_dump_mutex);
>> + kfree(adev->reset_dump_reg_list);
>> + adev->reset_dump_reg_list = NULL;
>> + alloc_count = 0;
>> + adev->n_regs = 0;
>> + mutex_unlock(&adev->reset_dump_mutex);
>> + return -EFAULT;
>> +}
>> +
>> +
>> +
>> +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;
>> @@ -1618,6 +1710,7 @@ int amdgpu_debugfs_init(struct amdgpu_device
>> *adev)
>> if (!debugfs_initialized())
>> return 0;
>> + mutex_init(&adev->reset_dump_mutex);
>> ent = debugfs_create_file("amdgpu_preempt_ib", 0600, root, adev,
>> &fops_ib_preempt);
>> if (IS_ERR(ent)) {
>> @@ -1672,6 +1765,8 @@ 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;
>
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