Am 17.02.22 um 10:44 schrieb Lazar, Lijo:
On 2/17/2022 1:30 PM, Christian König wrote:
Am 17.02.22 um 08:54 schrieb Somalapuram, Amaranath:
On 2/16/2022 8:26 PM, Christian König wrote:
Am 16.02.22 um 14:11 schrieb Somalapuram, Amaranath:
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@xxxxxxx>
---
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.
krealloc_array should be inside lock or outside lock? this may be
problem.
This *must* be outside the lock because we need to take the lock
during GPU reset which has a dependency to not allocate memory or
wait for locks under which memory is allocated.
That's why I said you need an approach which first parses the string
from userspace, build up the register list and then swap that with
the existing one while holding the lock.
Another approach would be to just protect debugfs write with
down_read(&adev->reset_sem) or reset domain semaphore.
No, exactly that doesn't work.
See the down_write(&adev->reset_sem) would then wait for this reader and
the reader is allocating memory and allocating memory might wait for the
reset to finish => deadlock.
Regards,
Christian.
Other than that if apps are trying to read and modify the list at the
same time, probably we should leave that to user mode since this is
mainly a debug feature.
Thanks,
Lijo
Regards,
Christian.
Regards,
S.Amarnath
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
No, that won't work like this. See you *must* always hold a lock
when reading or writing the array.
Otherwise it is perfectly possible that one thread sees only halve
of the updates of another thread.
The only alternative would be RCU, atomic replace and manual
barrier handling, but that would be complete overkill for that
feature.
Regards,
Christian.
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;
