diff mbox series

[v4,07/13] lib: test_hmm add ioctl to get zone device type

Message ID 20220531155629.20057-8-alex.sierra@amd.com (mailing list archive)
State New
Headers show
Series Add MEMORY_DEVICE_COHERENT for coherent device memory mapping | expand

Commit Message

Sierra Guiza, Alejandro (Alex) May 31, 2022, 3:56 p.m. UTC 
new ioctl cmd added to query zone device type. This will be
used once the test_hmm adds zone device coherent type.

Signed-off-by: Alex Sierra <alex.sierra@amd.com>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Alistair Poppple <apopple@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 lib/test_hmm.c      | 23 +++++++++++++++++++++--
 lib/test_hmm_uapi.h |  8 ++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)

Comments

Andrew Morton May 31, 2022, 5:31 p.m. UTC | #1 
On Tue, 31 May 2022 10:56:23 -0500 Alex Sierra <alex.sierra@amd.com> wrote:

> new ioctl cmd added to query zone device type. This will be
> used once the test_hmm adds zone device coherent type.
> 
> @@ -1026,6 +1027,15 @@ static int dmirror_snapshot(struct dmirror *dmirror,
>  	return ret;
>  }
>  
> +static int dmirror_get_device_type(struct dmirror *dmirror,
> +			    struct hmm_dmirror_cmd *cmd)
> +{
> +	mutex_lock(&dmirror->mutex);
> +	cmd->zone_device_type = dmirror->mdevice->zone_device_type;
> +	mutex_unlock(&dmirror->mutex);

What does the locking here do?

Presumably cmd->zone_device_type can become out of date the instant the
mutex is released, so what was the point in taking the mutex?

And does it make sense to return potentially out-of-date info to
userspace?  Perhaps this interface simply shouldn't exist?
Sierra Guiza, Alejandro (Alex) May 31, 2022, 7:19 p.m. UTC | #2 
On 5/31/2022 12:31 PM, Andrew Morton wrote:
> On Tue, 31 May 2022 10:56:23 -0500 Alex Sierra <alex.sierra@amd.com> wrote:
>
>> new ioctl cmd added to query zone device type. This will be
>> used once the test_hmm adds zone device coherent type.
>>
>> @@ -1026,6 +1027,15 @@ static int dmirror_snapshot(struct dmirror *dmirror,
>>   	return ret;
>>   }
>>   
>> +static int dmirror_get_device_type(struct dmirror *dmirror,
>> +			    struct hmm_dmirror_cmd *cmd)
>> +{
>> +	mutex_lock(&dmirror->mutex);
>> +	cmd->zone_device_type = dmirror->mdevice->zone_device_type;
>> +	mutex_unlock(&dmirror->mutex);
> What does the locking here do?
>
> Presumably cmd->zone_device_type can become out of date the instant the
> mutex is released, so what was the point in taking the mutex?

Actually this is not used at all. Thanks for finding it. Honestly, I 
don't remember what we used this type request for.
I will remove all related code  and send a new patch series version.

Regards,
Alex Sierra
>
> And does it make sense to return potentially out-of-date info to
> userspace?  Perhaps this interface simply shouldn't exist?
diff mbox series

Patch

diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index cfe632047839..7a27584484ce 100644
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -87,6 +87,7 @@  struct dmirror_chunk {
 struct dmirror_device {
 	struct cdev		cdevice;
 	struct hmm_devmem	*devmem;
+	unsigned int            zone_device_type;
 
 	unsigned int		devmem_capacity;
 	unsigned int		devmem_count;
@@ -1026,6 +1027,15 @@  static int dmirror_snapshot(struct dmirror *dmirror,
 	return ret;
 }
 
+static int dmirror_get_device_type(struct dmirror *dmirror,
+			    struct hmm_dmirror_cmd *cmd)
+{
+	mutex_lock(&dmirror->mutex);
+	cmd->zone_device_type = dmirror->mdevice->zone_device_type;
+	mutex_unlock(&dmirror->mutex);
+
+	return 0;
+}
 static long dmirror_fops_unlocked_ioctl(struct file *filp,
 					unsigned int command,
 					unsigned long arg)
@@ -1076,6 +1086,9 @@  static long dmirror_fops_unlocked_ioctl(struct file *filp,
 		ret = dmirror_snapshot(dmirror, &cmd);
 		break;
 
+	case HMM_DMIRROR_GET_MEM_DEV_TYPE:
+		ret = dmirror_get_device_type(dmirror, &cmd);
+		break;
 	default:
 		return -EINVAL;
 	}
@@ -1260,14 +1273,20 @@  static void dmirror_device_remove(struct dmirror_device *mdevice)
 static int __init hmm_dmirror_init(void)
 {
 	int ret;
-	int id;
+	int id = 0;
+	int ndevices = 0;
 
 	ret = alloc_chrdev_region(&dmirror_dev, 0, DMIRROR_NDEVICES,
 				  "HMM_DMIRROR");
 	if (ret)
 		goto err_unreg;
 
-	for (id = 0; id < DMIRROR_NDEVICES; id++) {
+	memset(dmirror_devices, 0, DMIRROR_NDEVICES * sizeof(dmirror_devices[0]));
+	dmirror_devices[ndevices++].zone_device_type =
+				HMM_DMIRROR_MEMORY_DEVICE_PRIVATE;
+	dmirror_devices[ndevices++].zone_device_type =
+				HMM_DMIRROR_MEMORY_DEVICE_PRIVATE;
+	for (id = 0; id < ndevices; id++) {
 		ret = dmirror_device_init(dmirror_devices + id, id);
 		if (ret)
 			goto err_chrdev;
diff --git a/lib/test_hmm_uapi.h b/lib/test_hmm_uapi.h
index f14dea5dcd06..17f842f1aa02 100644
--- a/lib/test_hmm_uapi.h
+++ b/lib/test_hmm_uapi.h
@@ -19,6 +19,7 @@ 
  * @npages: (in) number of pages to read/write
  * @cpages: (out) number of pages copied
  * @faults: (out) number of device page faults seen
+ * @zone_device_type: (out) zone device memory type
  */
 struct hmm_dmirror_cmd {
 	__u64		addr;
@@ -26,6 +27,7 @@  struct hmm_dmirror_cmd {
 	__u64		npages;
 	__u64		cpages;
 	__u64		faults;
+	__u64		zone_device_type;
 };
 
 /* Expose the address space of the calling process through hmm device file */
@@ -35,6 +37,7 @@  struct hmm_dmirror_cmd {
 #define HMM_DMIRROR_SNAPSHOT		_IOWR('H', 0x03, struct hmm_dmirror_cmd)
 #define HMM_DMIRROR_EXCLUSIVE		_IOWR('H', 0x04, struct hmm_dmirror_cmd)
 #define HMM_DMIRROR_CHECK_EXCLUSIVE	_IOWR('H', 0x05, struct hmm_dmirror_cmd)
+#define HMM_DMIRROR_GET_MEM_DEV_TYPE	_IOWR('H', 0x06, struct hmm_dmirror_cmd)
 
 /*
  * Values returned in hmm_dmirror_cmd.ptr for HMM_DMIRROR_SNAPSHOT.
@@ -62,4 +65,9 @@  enum {
 	HMM_DMIRROR_PROT_DEV_PRIVATE_REMOTE	= 0x30,
 };
 
+enum {
+	/* 0 is reserved to catch uninitialized type fields */
+	HMM_DMIRROR_MEMORY_DEVICE_PRIVATE = 1,
+};
+
 #endif /* _LIB_TEST_HMM_UAPI_H */