2021-04-09 03:46:01

by Shenming Lu

Subject: [RFC PATCH v3 1/8] iommu: Evolve the device fault reporting framework

This patch follows the discussion here:

https://lore.kernel.org/linux-acpi/YAaxjmJW+ZMvrhac@myrica/

Besides SVA/vSVA, such as VFIO may also enable (2nd level) IOPF to remove
pinning restriction. In order to better support more scenarios of using
device faults, we extend iommu_register_fault_handler() with flags and
introduce FAULT_REPORT_ to describe the device fault reporting capability
under a specific configuration.

Note that we don't further distinguish recoverable and unrecoverable faults
by flags in the fault reporting cap, having PAGE_FAULT_REPORT_ +
UNRECOV_FAULT_REPORT_ seems not a clean way.

In addition, still take VFIO as an example, in nested mode, the 1st level
and 2nd level fault reporting may be configured separately and currently
each device can only register one iommu dev fault handler, so we add a
handler update interface for this.

Signed-off-by: Shenming Lu <[email protected]>
---
.../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 3 +-
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 18 ++++--
drivers/iommu/iommu.c | 56 ++++++++++++++++++-
include/linux/iommu.h | 19 ++++++-
include/uapi/linux/iommu.h | 4 ++
5 files changed, 90 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
index ee66d1f4cb81..e6d766fb8f1a 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
@@ -482,7 +482,8 @@ static int arm_smmu_master_sva_enable_iopf(struct arm_smmu_master *master)
if (ret)
return ret;

- ret = iommu_register_device_fault_handler(dev, iommu_queue_iopf, dev);
+ ret = iommu_register_device_fault_handler(dev, iommu_queue_iopf,
+ FAULT_REPORT_FLAT, dev);
if (ret) {
iopf_queue_remove_device(master->smmu->evtq.iopf, dev);
return ret;
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 53abad8fdd91..51843f54a87f 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -1448,10 +1448,6 @@ static int arm_smmu_handle_evt(struct arm_smmu_device *smmu, u64 *evt)
return -EOPNOTSUPP;
}

- /* Stage-2 is always pinned at the moment */
- if (evt[1] & EVTQ_1_S2)
- return -EFAULT;
-
if (evt[1] & EVTQ_1_RnW)
perm |= IOMMU_FAULT_PERM_READ;
else
@@ -1469,26 +1465,36 @@ static int arm_smmu_handle_evt(struct arm_smmu_device *smmu, u64 *evt)
.flags = IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE,
.grpid = FIELD_GET(EVTQ_1_STAG, evt[1]),
.perm = perm,
- .addr = FIELD_GET(EVTQ_2_ADDR, evt[2]),
};

if (ssid_valid) {
flt->prm.flags |= IOMMU_FAULT_PAGE_REQUEST_PASID_VALID;
flt->prm.pasid = FIELD_GET(EVTQ_0_SSID, evt[0]);
}
+
+ if (evt[1] & EVTQ_1_S2) {
+ flt->prm.flags |= IOMMU_FAULT_PAGE_REQUEST_L2;
+ flt->prm.addr = FIELD_GET(EVTQ_3_IPA, evt[3]);
+ } else
+ flt->prm.addr = FIELD_GET(EVTQ_2_ADDR, evt[2]);
} else {
flt->type = IOMMU_FAULT_DMA_UNRECOV;
flt->event = (struct iommu_fault_unrecoverable) {
.reason = reason,
.flags = IOMMU_FAULT_UNRECOV_ADDR_VALID,
.perm = perm,
- .addr = FIELD_GET(EVTQ_2_ADDR, evt[2]),
};

if (ssid_valid) {
flt->event.flags |= IOMMU_FAULT_UNRECOV_PASID_VALID;
flt->event.pasid = FIELD_GET(EVTQ_0_SSID, evt[0]);
}
+
+ if (evt[1] & EVTQ_1_S2) {
+ flt->event.flags |= IOMMU_FAULT_UNRECOV_L2;
+ flt->event.addr = FIELD_GET(EVTQ_3_IPA, evt[3]);
+ } else
+ flt->event.addr = FIELD_GET(EVTQ_2_ADDR, evt[2]);
}

mutex_lock(&smmu->streams_mutex);
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index d0b0a15dba84..b50b526b45ac 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1056,6 +1056,40 @@ int iommu_group_unregister_notifier(struct iommu_group *group,
}
EXPORT_SYMBOL_GPL(iommu_group_unregister_notifier);

+/*
+ * iommu_update_device_fault_handler - Update the device fault handler via flags
+ * @dev: the device
+ * @mask: bits(not set) to clear
+ * @set: bits to set
+ *
+ * Update the device fault handler installed by
+ * iommu_register_device_fault_handler().
+ *
+ * Return 0 on success, or an error.
+ */
+int iommu_update_device_fault_handler(struct device *dev, u32 mask, u32 set)
+{
+ struct dev_iommu *param = dev->iommu;
+ int ret = 0;
+
+ if (!param)
+ return -EINVAL;
+
+ mutex_lock(&param->lock);
+
+ if (param->fault_param) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+
+ param->fault_param->flags = (param->fault_param->flags & mask) | set;
+
+out_unlock:
+ mutex_unlock(&param->lock);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(iommu_update_device_fault_handler);
+
/**
* iommu_register_device_fault_handler() - Register a device fault handler
* @dev: the device
@@ -1076,11 +1110,16 @@ EXPORT_SYMBOL_GPL(iommu_group_unregister_notifier);
*/
int iommu_register_device_fault_handler(struct device *dev,
iommu_dev_fault_handler_t handler,
- void *data)
+ u32 flags, void *data)
{
struct dev_iommu *param = dev->iommu;
int ret = 0;

+ /* Only under one configuration. */
+ if (flags & FAULT_REPORT_FLAT &&
+ flags & (FAULT_REPORT_NESTED_L1 | FAULT_REPORT_NESTED_L2))
+ return -EINVAL;
+
if (!param)
return -EINVAL;

@@ -1099,6 +1138,7 @@ int iommu_register_device_fault_handler(struct device *dev,
goto done_unlock;
}
param->fault_param->handler = handler;
+ param->fault_param->flags = flags;
param->fault_param->data = data;
mutex_init(&param->fault_param->lock);
INIT_LIST_HEAD(&param->fault_param->faults);
@@ -1177,6 +1217,20 @@ int iommu_report_device_fault(struct device *dev, struct iommu_fault_event *evt)
goto done_unlock;
}

+ if (!(fparam->flags & FAULT_REPORT_FLAT)) {
+ bool l2;
+
+ if (evt->fault.type == IOMMU_FAULT_PAGE_REQ)
+ l2 = evt->fault.prm.flags & IOMMU_FAULT_PAGE_REQUEST_L2;
+ if (evt->fault.type == IOMMU_FAULT_DMA_UNRECOV)
+ l2 = evt->fault.event.flags & IOMMU_FAULT_UNRECOV_L2;
+
+ if (l2 && !(fparam->flags & FAULT_REPORT_NESTED_L2))
+ return -EOPNOTSUPP;
+ if (!l2 && !(fparam->flags & FAULT_REPORT_NESTED_L1))
+ return -EOPNOTSUPP;
+ }
+
if (evt->fault.type == IOMMU_FAULT_PAGE_REQ &&
(evt->fault.prm.flags & IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE)) {
evt_pending = kmemdup(evt, sizeof(struct iommu_fault_event),
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 86d688c4418f..28dbca3c6d60 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -352,12 +352,19 @@ struct iommu_fault_event {
/**
* struct iommu_fault_param - per-device IOMMU fault data
* @handler: Callback function to handle IOMMU faults at device level
+ * @flags: FAULT_REPORT_ indicates the fault reporting capability under
+ * a specific configuration (1st/2nd-level-only(FLAT), or nested).
+ * Nested mode needs to specify which level/stage is concerned.
* @data: handler private data
* @faults: holds the pending faults which needs response
* @lock: protect pending faults list
*/
struct iommu_fault_param {
iommu_dev_fault_handler_t handler;
+#define FAULT_REPORT_FLAT (1 << 0)
+#define FAULT_REPORT_NESTED_L1 (1 << 1)
+#define FAULT_REPORT_NESTED_L2 (1 << 2)
+ u32 flags;
void *data;
struct list_head faults;
struct mutex lock;
@@ -509,9 +516,11 @@ extern int iommu_group_register_notifier(struct iommu_group *group,
struct notifier_block *nb);
extern int iommu_group_unregister_notifier(struct iommu_group *group,
struct notifier_block *nb);
+extern int iommu_update_device_fault_handler(struct device *dev,
+ u32 mask, u32 set);
extern int iommu_register_device_fault_handler(struct device *dev,
iommu_dev_fault_handler_t handler,
- void *data);
+ u32 flags, void *data);

extern int iommu_unregister_device_fault_handler(struct device *dev);

@@ -873,10 +882,16 @@ static inline int iommu_group_unregister_notifier(struct iommu_group *group,
return 0;
}

+static inline int iommu_update_device_fault_handler(struct device *dev,
+ u32 mask, u32 set)
+{
+ return -ENODEV;
+}
+
static inline
int iommu_register_device_fault_handler(struct device *dev,
iommu_dev_fault_handler_t handler,
- void *data)
+ u32 flags, void *data)
{
return -ENODEV;
}
diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
index e1d9e75f2c94..f6db9c8c970c 100644
--- a/include/uapi/linux/iommu.h
+++ b/include/uapi/linux/iommu.h
@@ -71,6 +71,7 @@ struct iommu_fault_unrecoverable {
#define IOMMU_FAULT_UNRECOV_PASID_VALID (1 << 0)
#define IOMMU_FAULT_UNRECOV_ADDR_VALID (1 << 1)
#define IOMMU_FAULT_UNRECOV_FETCH_ADDR_VALID (1 << 2)
+#define IOMMU_FAULT_UNRECOV_L2 (1 << 3)
__u32 flags;
__u32 pasid;
__u32 perm;
@@ -85,6 +86,8 @@ struct iommu_fault_unrecoverable {
* When IOMMU_FAULT_PAGE_RESPONSE_NEEDS_PASID is set, the page response
* must have the same PASID value as the page request. When it is clear,
* the page response should not have a PASID.
+ * If IOMMU_FAULT_PAGE_REQUEST_L2 is set, the fault occurred at the
+ * second level/stage, otherwise, occurred at the first level.
* @pasid: Process Address Space ID
* @grpid: Page Request Group Index
* @perm: requested page permissions (IOMMU_FAULT_PERM_* values)
@@ -96,6 +99,7 @@ struct iommu_fault_page_request {
#define IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE (1 << 1)
#define IOMMU_FAULT_PAGE_REQUEST_PRIV_DATA (1 << 2)
#define IOMMU_FAULT_PAGE_RESPONSE_NEEDS_PASID (1 << 3)
+#define IOMMU_FAULT_PAGE_REQUEST_L2 (1 << 4)
__u32 flags;
__u32 pasid;
__u32 grpid;
--
2.19.1

2021-05-19 18:30:18

by Alex Williamson

Subject: Re: [RFC PATCH v3 1/8] iommu: Evolve the device fault reporting framework

On Fri, 9 Apr 2021 11:44:13 +0800
Shenming Lu <[email protected]> wrote:

> This patch follows the discussion here:
>
> https://lore.kernel.org/linux-acpi/YAaxjmJW+ZMvrhac@myrica/
>
> Besides SVA/vSVA, such as VFIO may also enable (2nd level) IOPF to remove
> pinning restriction. In order to better support more scenarios of using
> device faults, we extend iommu_register_fault_handler() with flags and
> introduce FAULT_REPORT_ to describe the device fault reporting capability
> under a specific configuration.
>
> Note that we don't further distinguish recoverable and unrecoverable faults
> by flags in the fault reporting cap, having PAGE_FAULT_REPORT_ +
> UNRECOV_FAULT_REPORT_ seems not a clean way.
>
> In addition, still take VFIO as an example, in nested mode, the 1st level
> and 2nd level fault reporting may be configured separately and currently
> each device can only register one iommu dev fault handler, so we add a
> handler update interface for this.


IIUC, you're introducing flags for the fault handler callout, which
essentially allows the IOMMU layer to filter which types of faults the
handler can receive. You then need an update function to modify those
flags. Why can't the handler itself perform this filtering? For
instance in your vfio example, the handler registered by the type1
backend could itself return fault until the fault transfer path to the
device driver is established. Thanks,

Alex

2021-05-21 09:56:31

by Shenming Lu

Subject: Re: [RFC PATCH v3 1/8] iommu: Evolve the device fault reporting framework

On 2021/5/19 2:58, Alex Williamson wrote:
> On Fri, 9 Apr 2021 11:44:13 +0800
> Shenming Lu <[email protected]> wrote:
>
>> This patch follows the discussion here:
>>
>> https://lore.kernel.org/linux-acpi/YAaxjmJW+ZMvrhac@myrica/
>>
>> Besides SVA/vSVA, such as VFIO may also enable (2nd level) IOPF to remove
>> pinning restriction. In order to better support more scenarios of using
>> device faults, we extend iommu_register_fault_handler() with flags and
>> introduce FAULT_REPORT_ to describe the device fault reporting capability
>> under a specific configuration.
>>
>> Note that we don't further distinguish recoverable and unrecoverable faults
>> by flags in the fault reporting cap, having PAGE_FAULT_REPORT_ +
>> UNRECOV_FAULT_REPORT_ seems not a clean way.
>>
>> In addition, still take VFIO as an example, in nested mode, the 1st level
>> and 2nd level fault reporting may be configured separately and currently
>> each device can only register one iommu dev fault handler, so we add a
>> handler update interface for this.
>
>
> IIUC, you're introducing flags for the fault handler callout, which
> essentially allows the IOMMU layer to filter which types of faults the
> handler can receive. You then need an update function to modify those
> flags. Why can't the handler itself perform this filtering? For
> instance in your vfio example, the handler registered by the type1
> backend could itself return fault until the fault transfer path to the
> device driver is established. Thanks,

As discussed in [1]:

In nested IOPF, we have to figure out whether a fault comes from L1 or L2.
A SMMU stall event comes with this information, but a PRI page request doesn't.
The IOMMU driver can walk the page tables to find out the level information.
If the walk terminates at L1, further inject to the guest. Otherwise fix the
fault at L2 in VFIO. It's not efficient compared to hardware-provided info.

And in pinned case, if VFIO can tell the IOMMU driver that no L2 fault is
expected, there is no need to walk the page tables in the IOMMU driver?

[1] https://patchwork.kernel.org/project/linux-arm-kernel/patch/[email protected]/

Thanks,
Shenming

>
> Alex
>
> .
>