Much as I'd like to remove iommu_present(), the final remaining users
are proving stubbornly difficult to clean up, so kick that can down the
road and just rework it to preserve the current behaviour without
depending on bus ops. Since commit 57365a04c921 ("iommu: Move bus setup
to IOMMU device registration"), any registered IOMMU instance is already
considered "present" for every entry in iommu_buses, so it's simply a
case of validating the bus and checking we have at least once IOMMU.
Signed-off-by: Robin Murphy <[email protected]>
---
v3: Tweak to use the ops-based check rather than group-based, to
properly match the existing behaviour
v4: Just look for IOMMU instances instead of managed devices
---
drivers/iommu/iommu.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index f7793d1b5c3e..ef7feb0acc34 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1988,9 +1988,28 @@ int bus_iommu_probe(const struct bus_type *bus)
return 0;
}
+/**
+ * iommu_present() - make platform-specific assumptions about an IOMMU
+ * @bus: bus to check
+ *
+ * Do not use this function. You want device_iommu_mapped() instead.
+ *
+ * Return: true if some IOMMU is present and aware of devices on the given bus;
+ * in general it may not be the only IOMMU, and it may not have anything to do
+ * with whatever device you are ultimately interested in.
+ */
bool iommu_present(const struct bus_type *bus)
{
- return bus->iommu_ops != NULL;
+ bool ret = false;
+
+ for (int i = 0; i < ARRAY_SIZE(iommu_buses); i++) {
+ if (iommu_buses[i] == bus) {
+ spin_lock(&iommu_device_lock);
+ ret = !list_empty(&iommu_device_list);
+ spin_unlock(&iommu_device_lock);
+ }
+ }
+ return ret;
}
EXPORT_SYMBOL_GPL(iommu_present);
--
2.39.2.101.g768bb238c484.dirty
On Mon, Oct 02, 2023 at 02:49:10PM +0100, Robin Murphy wrote:
> Much as I'd like to remove iommu_present(), the final remaining users
> are proving stubbornly difficult to clean up, so kick that can down the
> road and just rework it to preserve the current behaviour without
> depending on bus ops. Since commit 57365a04c921 ("iommu: Move bus setup
> to IOMMU device registration"), any registered IOMMU instance is already
> considered "present" for every entry in iommu_buses, so it's simply a
> case of validating the bus and checking we have at least once IOMMU.
>
> Signed-off-by: Robin Murphy <[email protected]>
>
> ---
>
> v3: Tweak to use the ops-based check rather than group-based, to
> properly match the existing behaviour
> v4: Just look for IOMMU instances instead of managed devices
> ---
> drivers/iommu/iommu.c | 21 ++++++++++++++++++++-
> 1 file changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index f7793d1b5c3e..ef7feb0acc34 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1988,9 +1988,28 @@ int bus_iommu_probe(const struct bus_type *bus)
> return 0;
> }
>
> +/**
> + * iommu_present() - make platform-specific assumptions about an IOMMU
> + * @bus: bus to check
> + *
> + * Do not use this function. You want device_iommu_mapped() instead.
> + *
> + * Return: true if some IOMMU is present and aware of devices on the given bus;
> + * in general it may not be the only IOMMU, and it may not have anything to do
> + * with whatever device you are ultimately interested in.
> + */
> bool iommu_present(const struct bus_type *bus)
> {
> - return bus->iommu_ops != NULL;
> + bool ret = false;
> +
> + for (int i = 0; i < ARRAY_SIZE(iommu_buses); i++) {
> + if (iommu_buses[i] == bus) {
> + spin_lock(&iommu_device_lock);
> + ret = !list_empty(&iommu_device_list);
> + spin_unlock(&iommu_device_lock);
> + }
Add here:
return ret;
> + }
> + return ret;
And this becomes
return false
?
Regardless
Reviewed-by: Jason Gunthorpe <[email protected]>
Jason
On 02/10/2023 3:17 pm, Jason Gunthorpe wrote:
> On Mon, Oct 02, 2023 at 02:49:10PM +0100, Robin Murphy wrote:
>> Much as I'd like to remove iommu_present(), the final remaining users
>> are proving stubbornly difficult to clean up, so kick that can down the
>> road and just rework it to preserve the current behaviour without
>> depending on bus ops. Since commit 57365a04c921 ("iommu: Move bus setup
>> to IOMMU device registration"), any registered IOMMU instance is already
>> considered "present" for every entry in iommu_buses, so it's simply a
>> case of validating the bus and checking we have at least once IOMMU.
>>
>> Signed-off-by: Robin Murphy <[email protected]>
>>
>> ---
>>
>> v3: Tweak to use the ops-based check rather than group-based, to
>> properly match the existing behaviour
>> v4: Just look for IOMMU instances instead of managed devices
>> ---
>> drivers/iommu/iommu.c | 21 ++++++++++++++++++++-
>> 1 file changed, 20 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>> index f7793d1b5c3e..ef7feb0acc34 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -1988,9 +1988,28 @@ int bus_iommu_probe(const struct bus_type *bus)
>> return 0;
>> }
>>
>> +/**
>> + * iommu_present() - make platform-specific assumptions about an IOMMU
>> + * @bus: bus to check
>> + *
>> + * Do not use this function. You want device_iommu_mapped() instead.
>> + *
>> + * Return: true if some IOMMU is present and aware of devices on the given bus;
>> + * in general it may not be the only IOMMU, and it may not have anything to do
>> + * with whatever device you are ultimately interested in.
>> + */
>> bool iommu_present(const struct bus_type *bus)
>> {
>> - return bus->iommu_ops != NULL;
>> + bool ret = false;
>> +
>> + for (int i = 0; i < ARRAY_SIZE(iommu_buses); i++) {
>> + if (iommu_buses[i] == bus) {
>> + spin_lock(&iommu_device_lock);
>> + ret = !list_empty(&iommu_device_list);
>> + spin_unlock(&iommu_device_lock);
>> + }
>
> Add here:
>
> return ret;
>
>> + }
>> + return ret;
>
> And this becomes
>
> return false
>
> ?
My aim here was for the smallest, simplest code, given that what we
still really want is no code, and this is basically only being retained
to serve that one tricky Tegra callsite. I guess I could have also added
"&& !ret" to the loop condition, but either way since this should never
be on a hot path I figured it's not worth the bother just to save a
handful of extra comparisons.
> Regardless
>
> Reviewed-by: Jason Gunthorpe <[email protected]>
Thanks!
Robin.