[v12,13/16] iommu: Improve iopf_queue_remove_device()

Commit Message

Baolu Lu Feb. 7, 2024, 1:33 a.m. UTC

Convert iopf_queue_remove_device() to return void instead of an error code,
as the return value is never used. This removal helper is designed to be
never-failed, so there's no need for error handling.

Ack all outstanding page requests from the device with the response code of
IOMMU_PAGE_RESP_INVALID, indicating device should not attempt any retry.

Add comments to this helper explaining the steps involved in removing a
device from the iopf queue and disabling its PRI. The individual drivers
are expected to be adjusted accordingly. Here we just define the expected
behaviors of the individual iommu driver from the core's perspective.

Suggested-by: Jason Gunthorpe <[e-mail]>
Signed-off-by: Lu Baolu <[e-mail]>
Reviewed-by: Jason Gunthorpe <[e-mail]>
Tested-by: Yan Zhao <[e-mail]>
---
 include/linux/iommu.h       |  5 ++--
 drivers/iommu/intel/iommu.c |  7 +----
 drivers/iommu/io-pgfault.c  | 59 ++++++++++++++++++++++++-------------
 3 files changed, 41 insertions(+), 30 deletions(-)

Comments

Tian, Kevin Feb. 7, 2024, 2:50 a.m. UTC | #1

> From: Lu Baolu <[e-mail]>
> Sent: Wednesday, February 7, 2024 9:33 AM
> 
> Convert iopf_queue_remove_device() to return void instead of an error code,
> as the return value is never used. This removal helper is designed to be
> never-failed, so there's no need for error handling.
> 
> Ack all outstanding page requests from the device with the response code of
> IOMMU_PAGE_RESP_INVALID, indicating device should not attempt any retry.
> 
> Add comments to this helper explaining the steps involved in removing a
> device from the iopf queue and disabling its PRI. The individual drivers
> are expected to be adjusted accordingly. Here we just define the expected
> behaviors of the individual iommu driver from the core's perspective.
> 
> Suggested-by: Jason Gunthorpe <[e-mail]>
> Signed-off-by: Lu Baolu <[e-mail]>
> Reviewed-by: Jason Gunthorpe <[e-mail]>
> Tested-by: Yan Zhao <[e-mail]>

Reviewed-by: Kevin Tian <[e-mail]>, with one nit:

> + * Removing a device from an iopf_queue. It's recommended to follow
> these
> + * steps when removing a device:
>   *
> - * Return: 0 on success and <0 on error.
> + * - Disable new PRI reception: Turn off PRI generation in the IOMMU
> hardware
> + *   and flush any hardware page request queues. This should be done
> before
> + *   calling into this helper.
> + * - Acknowledge all outstanding PRQs to the device: Respond to all
> outstanding
> + *   page requests with IOMMU_PAGE_RESP_INVALID, indicating the device
> should
> + *   not retry. This helper function handles this.

this implies calling iopf_queue_remove_device() here.

> + * - Disable PRI on the device: After calling this helper, the caller could
> + *   then disable PRI on the device.
> + * - Call iopf_queue_remove_device(): Calling iopf_queue_remove_device()
> + *   essentially disassociates the device. The fault_param might still exist,
> + *   but iommu_page_response() will do nothing. The device fault parameter
> + *   reference count has been properly passed from
> iommu_report_device_fault()
> + *   to the fault handling work, and will eventually be released after
> + *   iommu_page_response().
>   */

but here it suggests calling iopf_queue_remove_device() again. If the comment
is just about to detail the behavior with that invocation shouldn't it be merged
with the previous one instead of pretending to be the final step for driver
to call?

Baolu Lu Feb. 7, 2024, 12:29 p.m. UTC | #2

On 2024/2/7 10:50, Tian, Kevin wrote:
>> From: Lu Baolu<[e-mail]>
>> Sent: Wednesday, February 7, 2024 9:33 AM
>>
>> Convert iopf_queue_remove_device() to return void instead of an error code,
>> as the return value is never used. This removal helper is designed to be
>> never-failed, so there's no need for error handling.
>>
>> Ack all outstanding page requests from the device with the response code of
>> IOMMU_PAGE_RESP_INVALID, indicating device should not attempt any retry.
>>
>> Add comments to this helper explaining the steps involved in removing a
>> device from the iopf queue and disabling its PRI. The individual drivers
>> are expected to be adjusted accordingly. Here we just define the expected
>> behaviors of the individual iommu driver from the core's perspective.
>>
>> Suggested-by: Jason Gunthorpe<[e-mail]>
>> Signed-off-by: Lu Baolu<[e-mail]>
>> Reviewed-by: Jason Gunthorpe<[e-mail]>
>> Tested-by: Yan Zhao<[e-mail]>
> Reviewed-by: Kevin Tian<[e-mail]>, with one nit:
> 
>> + * Removing a device from an iopf_queue. It's recommended to follow
>> these
>> + * steps when removing a device:
>>    *
>> - * Return: 0 on success and <0 on error.
>> + * - Disable new PRI reception: Turn off PRI generation in the IOMMU
>> hardware
>> + *   and flush any hardware page request queues. This should be done
>> before
>> + *   calling into this helper.
>> + * - Acknowledge all outstanding PRQs to the device: Respond to all
>> outstanding
>> + *   page requests with IOMMU_PAGE_RESP_INVALID, indicating the device
>> should
>> + *   not retry. This helper function handles this.
> this implies calling iopf_queue_remove_device() here.
> 
>> + * - Disable PRI on the device: After calling this helper, the caller could
>> + *   then disable PRI on the device.
>> + * - Call iopf_queue_remove_device(): Calling iopf_queue_remove_device()
>> + *   essentially disassociates the device. The fault_param might still exist,
>> + *   but iommu_page_response() will do nothing. The device fault parameter
>> + *   reference count has been properly passed from
>> iommu_report_device_fault()
>> + *   to the fault handling work, and will eventually be released after
>> + *   iommu_page_response().
>>    */
> but here it suggests calling iopf_queue_remove_device() again. If the comment
> is just about to detail the behavior with that invocation shouldn't it be merged
> with the previous one instead of pretending to be the final step for driver
> to call?

Above just explains the behavior of calling iopf_queue_remove_device().

Best regards,
baolu

Vasant Hegde Feb. 7, 2024, 5:59 p.m. UTC | #3

Hi Baolu,

On 2/7/2024 5:59 PM, Baolu Lu wrote:
> On 2024/2/7 10:50, Tian, Kevin wrote:
>>> From: Lu Baolu<[e-mail]>
>>> Sent: Wednesday, February 7, 2024 9:33 AM
>>>
>>> Convert iopf_queue_remove_device() to return void instead of an error code,
>>> as the return value is never used. This removal helper is designed to be
>>> never-failed, so there's no need for error handling.
>>>
>>> Ack all outstanding page requests from the device with the response code of
>>> IOMMU_PAGE_RESP_INVALID, indicating device should not attempt any retry.
>>>
>>> Add comments to this helper explaining the steps involved in removing a
>>> device from the iopf queue and disabling its PRI. The individual drivers
>>> are expected to be adjusted accordingly. Here we just define the expected
>>> behaviors of the individual iommu driver from the core's perspective.
>>>
>>> Suggested-by: Jason Gunthorpe<[e-mail]>
>>> Signed-off-by: Lu Baolu<[e-mail]>
>>> Reviewed-by: Jason Gunthorpe<[e-mail]>
>>> Tested-by: Yan Zhao<[e-mail]>
>> Reviewed-by: Kevin Tian<[e-mail]>, with one nit:
>>
>>> + * Removing a device from an iopf_queue. It's recommended to follow
>>> these
>>> + * steps when removing a device:
>>>    *
>>> - * Return: 0 on success and <0 on error.
>>> + * - Disable new PRI reception: Turn off PRI generation in the IOMMU
>>> hardware
>>> + *   and flush any hardware page request queues. This should be done
>>> before
>>> + *   calling into this helper.
>>> + * - Acknowledge all outstanding PRQs to the device: Respond to all
>>> outstanding
>>> + *   page requests with IOMMU_PAGE_RESP_INVALID, indicating the device
>>> should
>>> + *   not retry. This helper function handles this.
>> this implies calling iopf_queue_remove_device() here.
>>
>>> + * - Disable PRI on the device: After calling this helper, the caller could
>>> + *   then disable PRI on the device.
>>> + * - Call iopf_queue_remove_device(): Calling iopf_queue_remove_device()
>>> + *   essentially disassociates the device. The fault_param might still exist,
>>> + *   but iommu_page_response() will do nothing. The device fault parameter
>>> + *   reference count has been properly passed from
>>> iommu_report_device_fault()
>>> + *   to the fault handling work, and will eventually be released after
>>> + *   iommu_page_response().
>>>    */
>> but here it suggests calling iopf_queue_remove_device() again. If the comment
>> is just about to detail the behavior with that invocation shouldn't it be merged
>> with the previous one instead of pretending to be the final step for driver
>> to call?
> 
> Above just explains the behavior of calling iopf_queue_remove_device().

Can you please leave a line -OR- move this to previous para? Otherwise we will
get confused.

-Vasant

Baolu Lu Feb. 8, 2024, 1:32 a.m. UTC | #4

On 2024/2/8 1:59, Vasant Hegde wrote:
> Hi Baolu,
> 
> On 2/7/2024 5:59 PM, Baolu Lu wrote:
>> On 2024/2/7 10:50, Tian, Kevin wrote:
>>>> From: Lu Baolu<[e-mail]>
>>>> Sent: Wednesday, February 7, 2024 9:33 AM
>>>>
>>>> Convert iopf_queue_remove_device() to return void instead of an error code,
>>>> as the return value is never used. This removal helper is designed to be
>>>> never-failed, so there's no need for error handling.
>>>>
>>>> Ack all outstanding page requests from the device with the response code of
>>>> IOMMU_PAGE_RESP_INVALID, indicating device should not attempt any retry.
>>>>
>>>> Add comments to this helper explaining the steps involved in removing a
>>>> device from the iopf queue and disabling its PRI. The individual drivers
>>>> are expected to be adjusted accordingly. Here we just define the expected
>>>> behaviors of the individual iommu driver from the core's perspective.
>>>>
>>>> Suggested-by: Jason Gunthorpe<[e-mail]>
>>>> Signed-off-by: Lu Baolu<[e-mail]>
>>>> Reviewed-by: Jason Gunthorpe<[e-mail]>
>>>> Tested-by: Yan Zhao<[e-mail]>
>>> Reviewed-by: Kevin Tian<[e-mail]>, with one nit:
>>>
>>>> + * Removing a device from an iopf_queue. It's recommended to follow
>>>> these
>>>> + * steps when removing a device:
>>>>     *
>>>> - * Return: 0 on success and <0 on error.
>>>> + * - Disable new PRI reception: Turn off PRI generation in the IOMMU
>>>> hardware
>>>> + *   and flush any hardware page request queues. This should be done
>>>> before
>>>> + *   calling into this helper.
>>>> + * - Acknowledge all outstanding PRQs to the device: Respond to all
>>>> outstanding
>>>> + *   page requests with IOMMU_PAGE_RESP_INVALID, indicating the device
>>>> should
>>>> + *   not retry. This helper function handles this.
>>> this implies calling iopf_queue_remove_device() here.
>>>
>>>> + * - Disable PRI on the device: After calling this helper, the caller could
>>>> + *   then disable PRI on the device.
>>>> + * - Call iopf_queue_remove_device(): Calling iopf_queue_remove_device()
>>>> + *   essentially disassociates the device. The fault_param might still exist,
>>>> + *   but iommu_page_response() will do nothing. The device fault parameter
>>>> + *   reference count has been properly passed from
>>>> iommu_report_device_fault()
>>>> + *   to the fault handling work, and will eventually be released after
>>>> + *   iommu_page_response().
>>>>     */
>>> but here it suggests calling iopf_queue_remove_device() again. If the comment
>>> is just about to detail the behavior with that invocation shouldn't it be merged
>>> with the previous one instead of pretending to be the final step for driver
>>> to call?
>>
>> Above just explains the behavior of calling iopf_queue_remove_device().
> 
> Can you please leave a line -OR- move this to previous para? Otherwise we will
> get confused.

Sure. I will make it look like below.

/**
  * iopf_queue_remove_device - Remove producer from fault queue
  * @queue: IOPF queue
  * @dev: device to remove
  *
  * Removing a device from an iopf_queue. It's recommended to follow these
  * steps when removing a device:
  *
  * - Disable new PRI reception: Turn off PRI generation in the IOMMU 
hardware
  *   and flush any hardware page request queues. This should be done before
  *   calling into this helper.
  * - Acknowledge all outstanding PRQs to the device: Respond to all 
outstanding
  *   page requests with IOMMU_PAGE_RESP_INVALID, indicating the device 
should
  *   not retry. This helper function handles this.
  * - Disable PRI on the device: After calling this helper, the caller could
  *   then disable PRI on the device.
  *
  * Calling iopf_queue_remove_device() essentially disassociates the device.
  * The fault_param might still exist, but iommu_page_response() will do
  * nothing. The device fault parameter reference count has been properly
  * passed from iommu_report_device_fault() to the fault handling work, and
  * will eventually be released after iommu_page_response().
  */

Best regards,
baolu

Vasant Hegde Feb. 8, 2024, 5:06 a.m. UTC | #5

On 2/8/2024 7:02 AM, Baolu Lu wrote:
> On 2024/2/8 1:59, Vasant Hegde wrote:
>> Hi Baolu,
>>
>> On 2/7/2024 5:59 PM, Baolu Lu wrote:
>>> On 2024/2/7 10:50, Tian, Kevin wrote:
>>>>> From: Lu Baolu<[e-mail]>
>>>>> Sent: Wednesday, February 7, 2024 9:33 AM
>>>>>
>>>>> Convert iopf_queue_remove_device() to return void instead of an error code,
>>>>> as the return value is never used. This removal helper is designed to be
>>>>> never-failed, so there's no need for error handling.
>>>>>
>>>>> Ack all outstanding page requests from the device with the response code of
>>>>> IOMMU_PAGE_RESP_INVALID, indicating device should not attempt any retry.
>>>>>
>>>>> Add comments to this helper explaining the steps involved in removing a
>>>>> device from the iopf queue and disabling its PRI. The individual drivers
>>>>> are expected to be adjusted accordingly. Here we just define the expected
>>>>> behaviors of the individual iommu driver from the core's perspective.
>>>>>
>>>>> Suggested-by: Jason Gunthorpe<[e-mail]>
>>>>> Signed-off-by: Lu Baolu<[e-mail]>
>>>>> Reviewed-by: Jason Gunthorpe<[e-mail]>
>>>>> Tested-by: Yan Zhao<[e-mail]>
>>>> Reviewed-by: Kevin Tian<[e-mail]>, with one nit:
>>>>
>>>>> + * Removing a device from an iopf_queue. It's recommended to follow
>>>>> these
>>>>> + * steps when removing a device:
>>>>>     *
>>>>> - * Return: 0 on success and <0 on error.
>>>>> + * - Disable new PRI reception: Turn off PRI generation in the IOMMU
>>>>> hardware
>>>>> + *   and flush any hardware page request queues. This should be done
>>>>> before
>>>>> + *   calling into this helper.
>>>>> + * - Acknowledge all outstanding PRQs to the device: Respond to all
>>>>> outstanding
>>>>> + *   page requests with IOMMU_PAGE_RESP_INVALID, indicating the device
>>>>> should
>>>>> + *   not retry. This helper function handles this.
>>>> this implies calling iopf_queue_remove_device() here.
>>>>
>>>>> + * - Disable PRI on the device: After calling this helper, the caller could
>>>>> + *   then disable PRI on the device.
>>>>> + * - Call iopf_queue_remove_device(): Calling iopf_queue_remove_device()
>>>>> + *   essentially disassociates the device. The fault_param might still exist,
>>>>> + *   but iommu_page_response() will do nothing. The device fault parameter
>>>>> + *   reference count has been properly passed from
>>>>> iommu_report_device_fault()
>>>>> + *   to the fault handling work, and will eventually be released after
>>>>> + *   iommu_page_response().
>>>>>     */
>>>> but here it suggests calling iopf_queue_remove_device() again. If the comment
>>>> is just about to detail the behavior with that invocation shouldn't it be
>>>> merged
>>>> with the previous one instead of pretending to be the final step for driver
>>>> to call?
>>>
>>> Above just explains the behavior of calling iopf_queue_remove_device().
>>
>> Can you please leave a line -OR- move this to previous para? Otherwise we will
>> get confused.
> 
> Sure. I will make it look like below.
> 
> /**
>  * iopf_queue_remove_device - Remove producer from fault queue
>  * @queue: IOPF queue
>  * @dev: device to remove
>  *
>  * Removing a device from an iopf_queue. It's recommended to follow these
>  * steps when removing a device:
>  *
>  * - Disable new PRI reception: Turn off PRI generation in the IOMMU hardware
>  *   and flush any hardware page request queues. This should be done before
>  *   calling into this helper.
>  * - Acknowledge all outstanding PRQs to the device: Respond to all outstanding
>  *   page requests with IOMMU_PAGE_RESP_INVALID, indicating the device should
>  *   not retry. This helper function handles this.
>  * - Disable PRI on the device: After calling this helper, the caller could
>  *   then disable PRI on the device.
>  *
>  * Calling iopf_queue_remove_device() essentially disassociates the device.
>  * The fault_param might still exist, but iommu_page_response() will do
>  * nothing. The device fault parameter reference count has been properly
>  * passed from iommu_report_device_fault() to the fault handling work, and
>  * will eventually be released after iommu_page_response().
>  */

Looks good. Thank you.

-Vasant

Patch

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 1e9161ae95da..92dfd9b94577 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -1542,7 +1542,7 @@  iommu_sva_domain_alloc(struct device *dev, struct mm_struct *mm)
 
 #ifdef CONFIG_IOMMU_IOPF
 int iopf_queue_add_device(struct iopf_queue *queue, struct device *dev);
-int iopf_queue_remove_device(struct iopf_queue *queue, struct device *dev);
+void iopf_queue_remove_device(struct iopf_queue *queue, struct device *dev);
 int iopf_queue_flush_dev(struct device *dev);
 struct iopf_queue *iopf_queue_alloc(const char *name);
 void iopf_queue_free(struct iopf_queue *queue);
@@ -1558,10 +1558,9 @@  iopf_queue_add_device(struct iopf_queue *queue, struct device *dev)
 	return -ENODEV;
 }
 
-static inline int
+static inline void
 iopf_queue_remove_device(struct iopf_queue *queue, struct device *dev)
 {
-	return -ENODEV;
 }
 
 static inline int iopf_queue_flush_dev(struct device *dev)
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 29a12f289e2e..a81a2be9b870 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -4455,12 +4455,7 @@  static int intel_iommu_disable_iopf(struct device *dev)
 	 */
 	pci_disable_pri(to_pci_dev(dev));
 	info->pri_enabled = 0;
-
-	/*
-	 * With PRI disabled and outstanding PRQs drained, removing device
-	 * from iopf queue should never fail.
-	 */
-	WARN_ON(iopf_queue_remove_device(iommu->iopf_queue, dev));
+	iopf_queue_remove_device(iommu->iopf_queue, dev);
 
 	return 0;
 }
diff --git a/drivers/iommu/io-pgfault.c b/drivers/iommu/io-pgfault.c
index ce7058892b59..b20f49bd5e4a 100644
--- a/drivers/iommu/io-pgfault.c
+++ b/drivers/iommu/io-pgfault.c
@@ -448,50 +448,67 @@  EXPORT_SYMBOL_GPL(iopf_queue_add_device);
  * @queue: IOPF queue
  * @dev: device to remove
  *
- * Caller makes sure that no more faults are reported for this device.
+ * Removing a device from an iopf_queue. It's recommended to follow these
+ * steps when removing a device:
  *
- * Return: 0 on success and <0 on error.
+ * - Disable new PRI reception: Turn off PRI generation in the IOMMU hardware
+ *   and flush any hardware page request queues. This should be done before
+ *   calling into this helper.
+ * - Acknowledge all outstanding PRQs to the device: Respond to all outstanding
+ *   page requests with IOMMU_PAGE_RESP_INVALID, indicating the device should
+ *   not retry. This helper function handles this.
+ * - Disable PRI on the device: After calling this helper, the caller could
+ *   then disable PRI on the device.
+ * - Call iopf_queue_remove_device(): Calling iopf_queue_remove_device()
+ *   essentially disassociates the device. The fault_param might still exist,
+ *   but iommu_page_response() will do nothing. The device fault parameter
+ *   reference count has been properly passed from iommu_report_device_fault()
+ *   to the fault handling work, and will eventually be released after
+ *   iommu_page_response().
  */
-int iopf_queue_remove_device(struct iopf_queue *queue, struct device *dev)
+void iopf_queue_remove_device(struct iopf_queue *queue, struct device *dev)
 {
-	int ret = 0;
 	struct iopf_fault *iopf, *next;
+	struct iommu_page_response resp;
 	struct dev_iommu *param = dev->iommu;
 	struct iommu_fault_param *fault_param;
+	const struct iommu_ops *ops = dev_iommu_ops(dev);
 
 	mutex_lock(&queue->lock);
 	mutex_lock(&param->lock);
 	fault_param = rcu_dereference_check(param->fault_param,
 					    lockdep_is_held(&param->lock));
-	if (!fault_param) {
-		ret = -ENODEV;
-		goto unlock;
-	}
-
-	if (fault_param->queue != queue) {
-		ret = -EINVAL;
-		goto unlock;
-	}
 
-	if (!list_empty(&fault_param->faults)) {
-		ret = -EBUSY;
+	if (WARN_ON(!fault_param || fault_param->queue != queue))
 		goto unlock;
-	}
-
-	list_del(&fault_param->queue_list);
 
-	/* Just in case some faults are still stuck */
+	mutex_lock(&fault_param->lock);
 	list_for_each_entry_safe(iopf, next, &fault_param->partial, list)
 		kfree(iopf);
 
+	list_for_each_entry_safe(iopf, next, &fault_param->faults, list) {
+		memset(&resp, 0, sizeof(struct iommu_page_response));
+		resp.pasid = iopf->fault.prm.pasid;
+		resp.grpid = iopf->fault.prm.grpid;
+		resp.code = IOMMU_PAGE_RESP_INVALID;
+
+		if (iopf->fault.prm.flags & IOMMU_FAULT_PAGE_RESPONSE_NEEDS_PASID)
+			resp.flags = IOMMU_PAGE_RESP_PASID_VALID;
+
+		ops->page_response(dev, iopf, &resp);
+		list_del(&iopf->list);
+		kfree(iopf);
+	}
+	mutex_unlock(&fault_param->lock);
+
+	list_del(&fault_param->queue_list);
+
 	/* dec the ref owned by iopf_queue_add_device() */
 	rcu_assign_pointer(param->fault_param, NULL);
 	iopf_put_dev_fault_param(fault_param);
 unlock:
 	mutex_unlock(&param->lock);
 	mutex_unlock(&queue->lock);
-
-	return ret;
 }
 EXPORT_SYMBOL_GPL(iopf_queue_remove_device);