Re: [PATCH v6 1/9] iommu: Add APIs for multiple domains per device
From: Lu Baolu
Date: Wed Feb 13 2019 - 20:43:47 EST
Hi Jean,
On 2/13/19 7:55 PM, Jean-Philippe Brucker wrote:
Hi,
I have a few boring nits and one question below
Thanks a lot for reviewing my patch.
On 13/02/2019 04:02, Lu Baolu wrote:
Sharing a physical PCI device in a finer-granularity way
is becoming a consensus in the industry. IOMMU vendors
are also engaging efforts to support such sharing as well
as possible. Among the efforts, the capability of support
finer-granularity DMA isolation is a common requirement
due to the security consideration. With finer-granularity
DMA isolation, all DMA requests out of or to a subset of
a physical PCI device can be protected by the IOMMU.
That last sentence seems strange, how about "With finer-granularity DMA
isolation, subsets of a PCI function can be isolated from each others by
the IOMMU."
Yours looks better. Thanks!
As a
result, there is a request in software to attach multiple
domains to a physical PCI device. One example of such use
model is the Intel Scalable IOV [1] [2]. The Intel vt-d
3.0 spec [3] introduces the scalable mode which enables
PASID granularity DMA isolation.
This adds the APIs to support multiple domains per device.
In order to ease the discussions, we call it 'a domain in
auxiliary mode' or simply 'auxiliary domain' when multiple
domains are attached to a physical device.
The APIs include:
* iommu_dev_has_feature(dev, IOMMU_DEV_FEAT_AUX)
- Check whether both IOMMU and device support IOMMU aux
domain feature. Below aux-domain specific interfaces
are available only after this returns true.
s/after/if/ since calling has_feature() shouldn't be a prerequisite to
using the aux-domain interface (unlike calling enable_feature()).
After reconsideration, I think my comments about this API isn't
correct. It should be like,
* iommu_dev_has_feature(dev, IOMMU_DEV_FEAT_AUX)
- Detect both IOMMU and PCI endpoint devices supporting the feature
(aux-domain here) without host driver dependency.
* iommu_dev_feature_enabled(dev, IOMMU_DEV_FEAT_AUX)
- Check the enabling status of the feature (aux-domain here). The
aux-domain interfaces are available only if this returns true.
* iommu_dev_enable/disable_feature(dev, IOMMU_DEV_FEAT_AUX)
- Enable/disable device specific aux-domain feature.
* iommu_dev_feature_enabled(dev, IOMMU_DEV_FEAT_AUX)
- Check whether the aux domain specific feature enabled or
not.
"is enabled"
Sure.
* iommu_aux_attach_device(domain, dev)
- Attaches @domain to @dev in the auxiliary mode. Multiple
domains could be attached to a single device in the
auxiliary mode with each domain representing an isolated
address space for an assignable subset of the device.
* iommu_aux_detach_device(domain, dev)
- Detach @domain which has been attached to @dev in the
auxiliary mode.
* iommu_aux_get_pasid(domain, dev)
- Return ID used for finer-granularity DMA translation.
For the Intel Scalable IOV usage model, this will be
a PASID. The device which supports Scalable IOV needs
to write this ID to the device register so that DMA
requests could be tagged with a right PASID prefix.
This has been updated with the latest proposal from Joerg
posted here [5].
Many people involved in discussions of this design.
Kevin Tian <kevin.tian@xxxxxxxxx>
Liu Yi L <yi.l.liu@xxxxxxxxx>
Ashok Raj <ashok.raj@xxxxxxxxx>
Sanjay Kumar <sanjay.k.kumar@xxxxxxxxx>
Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
Alex Williamson <alex.williamson@xxxxxxxxxx>
Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx>
Joerg Roedel <joro@xxxxxxxxxx>
and some discussions can be found here [4] [5].
[1]
https://software.intel.com/en-us/download/intel-scalable-io-virtualization-technical-specification
[2] https://schd.ws/hosted_files/lc32018/00/LC3-SIOV-final.pdf
[3]
https://software.intel.com/en-us/download/intel-virtualization-technology-for-directed-io-architecture-specification
[4] https://lkml.org/lkml/2018/7/26/4
[5] https://www.spinics.net/lists/iommu/msg31874.html
Cc: Ashok Raj <ashok.raj@xxxxxxxxx>
Cc: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
Cc: Liu Yi L <yi.l.liu@xxxxxxxxx>
Suggested-by: Kevin Tian <kevin.tian@xxxxxxxxx>
Suggested-by: Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx>
Suggested-by: Joerg Roedel <jroedel@xxxxxxx>
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
drivers/iommu/iommu.c | 91 +++++++++++++++++++++++++++++++++++++++++++
include/linux/iommu.h | 70 +++++++++++++++++++++++++++++++++
2 files changed, 161 insertions(+)
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 3ed4db334341..d0b323e8357f 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2033,3 +2033,94 @@ int iommu_fwspec_add_ids(struct device *dev, u32
*ids, int num_ids)
return 0;
}
EXPORT_SYMBOL_GPL(iommu_fwspec_add_ids);
+
+/*
+ * Per device IOMMU features.
+ */
+bool iommu_dev_has_feature(struct device *dev, enum iommu_dev_features
feat)
+{
+ const struct iommu_ops *ops = dev->bus->iommu_ops;
+
+ if (ops && ops->dev_has_feat)
+ return ops->dev_has_feat(dev, feat);
+
+ return false;
+}
+EXPORT_SYMBOL_GPL(iommu_dev_has_feature);
+
+int iommu_dev_enable_feature(struct device *dev, enum
iommu_dev_features feat)
+{
+ const struct iommu_ops *ops = dev->bus->iommu_ops;
+
+ if (ops && ops->dev_enable_feat)
+ return ops->dev_enable_feat(dev, feat);
+
+ return -ENODEV;
+}
+EXPORT_SYMBOL_GPL(iommu_dev_enable_feature);
+
+int iommu_dev_disable_feature(struct device *dev, enum
iommu_dev_features feat)
+{
+ const struct iommu_ops *ops = dev->bus->iommu_ops;
+
+ if (ops && ops->dev_disable_feat)
+ return ops->dev_disable_feat(dev, feat);
+
+ return -ENODEV;
+}
+EXPORT_SYMBOL_GPL(iommu_dev_disable_feature);
+
+bool iommu_dev_feature_enabled(struct device *dev, enum
iommu_dev_features feat)
+{
+ const struct iommu_ops *ops = dev->bus->iommu_ops;
+
+ if (ops && ops->dev_feat_enabled)
+ return ops->dev_feat_enabled(dev, feat);
+
+ return false;
+}
+EXPORT_SYMBOL_GPL(iommu_dev_feature_enabled);
+
+/*
+ * Aux-domain specific attach/detach.
+ *
+ * Only works if iommu_dev_has_feature(dev, IOMMU_DEV_FEAT_AUX) returns
true.
Rather "Only works if iommu_dev_feature_enabled(dev, AUX) returns true"?
Yes. I will change this and above.
+ * Also, as long as domains are attached to a device through this
interface,
+ * any tries to call iommu_attach_device() should fail
(iommu_detach_device()
+ * can't fail, so we fail on the tryint to re-attach). This should make
"when trying to re-attach"
Sure.
us safe
+ * against a device being attached to a guest as a whole while there
are still
+ * pasid users on it (aux and sva).
A related question: is calling iommu_dev_disable_feat(dev, AUX) enough
to detach all auxiliary domains? I guess device drivers will always need
to tidy contexts up one by one, so maybe iommu_dev_disable_feat(dev,
AUX) can return -EBUSY in this case? I think we need to specify this in
a comment so device drivers know how to clean up.
Yes, -EBUSY sounds better.
iommu_dev_disable_feat() will not detach all aux-domains, it requires
the device drivers to do so before calling it. So if it sees anything
not cleaned up, it should return -EBUSY. And we should put it as a
comment for this API so that the device drivers know it.
Thanks,
Jean
Best regards,
Lu Baolu
+ */
+int iommu_aux_attach_device(struct iommu_domain *domain, struct device
*dev)
+{
+ int ret = -ENODEV;
+
+ if (domain->ops->aux_attach_dev)
+ ret = domain->ops->aux_attach_dev(domain, dev);
+
+ if (!ret)
+ trace_attach_device_to_domain(dev);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(iommu_aux_attach_device);
+
+void iommu_aux_detach_device(struct iommu_domain *domain, struct device
*dev)
+{
+ if (domain->ops->aux_detach_dev) {
+ domain->ops->aux_detach_dev(domain, dev);
+ trace_detach_device_from_domain(dev);
+ }
+}
+EXPORT_SYMBOL_GPL(iommu_aux_detach_device);
+
+int iommu_aux_get_pasid(struct iommu_domain *domain, struct device *dev)
+{
+ int ret = -ENODEV;
+
+ if (domain->ops->aux_get_pasid)
+ ret = domain->ops->aux_get_pasid(domain, dev);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(iommu_aux_get_pasid);
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index e90da6b6f3d1..831eb29b35c5 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -156,6 +156,11 @@ struct iommu_resv_region {
enum iommu_resv_type type;
};
+/* Per device IOMMU features */
+enum iommu_dev_features {
+ IOMMU_DEV_FEAT_AUX, /* Aux-domain feature */
+};
+
#ifdef CONFIG_IOMMU_API
/**
@@ -183,6 +188,11 @@ struct iommu_resv_region {
* @domain_window_enable: Configure and enable a particular window for
a domain
* @domain_window_disable: Disable a particular window for a domain
* @of_xlate: add OF master IDs to iommu grouping
+ * @dev_has/enable/disable_feat: per device entries to check/enable/disable
+ * iommu specific features.
+ * @dev_feat_enabled: check enabled feature
+ * @aux_attach/detach_dev: aux-domain specific attach/detach entries.
+ * @aux_get_pasid: get the pasid given an aux-domain
* @pgsize_bitmap: bitmap of all possible supported page sizes
*/
struct iommu_ops {
@@ -226,6 +236,17 @@ struct iommu_ops {
int (*of_xlate)(struct device *dev, struct of_phandle_args *args);
bool (*is_attach_deferred)(struct iommu_domain *domain, struct
device *dev);
+ /* Per device IOMMU features */
+ bool (*dev_has_feat)(struct device *dev, enum iommu_dev_features f);
+ bool (*dev_feat_enabled)(struct device *dev, enum
iommu_dev_features f);
+ int (*dev_enable_feat)(struct device *dev, enum
iommu_dev_features f);
+ int (*dev_disable_feat)(struct device *dev, enum
iommu_dev_features f);
+
+ /* Aux-domain specific attach/detach entries */
+ int (*aux_attach_dev)(struct iommu_domain *domain, struct device
*dev);
+ void (*aux_detach_dev)(struct iommu_domain *domain, struct
device *dev);
+ int (*aux_get_pasid)(struct iommu_domain *domain, struct device
*dev);
+
unsigned long pgsize_bitmap;
};
@@ -412,6 +433,14 @@ static inline void dev_iommu_fwspec_set(struct
device *dev,
int iommu_probe_device(struct device *dev);
void iommu_release_device(struct device *dev);
+bool iommu_dev_has_feature(struct device *dev, enum iommu_dev_features f);
+int iommu_dev_enable_feature(struct device *dev, enum
iommu_dev_features f);
+int iommu_dev_disable_feature(struct device *dev, enum
iommu_dev_features f);
+bool iommu_dev_feature_enabled(struct device *dev, enum
iommu_dev_features f);
+int iommu_aux_attach_device(struct iommu_domain *domain, struct device
*dev);
+void iommu_aux_detach_device(struct iommu_domain *domain, struct device
*dev);
+int iommu_aux_get_pasid(struct iommu_domain *domain, struct device *dev);
+
#else /* CONFIG_IOMMU_API */
struct iommu_ops {};
@@ -696,6 +725,47 @@ const struct iommu_ops
*iommu_ops_from_fwnode(struct fwnode_handle *fwnode)
return NULL;
}
+static inline bool
+iommu_dev_has_feature(struct device *dev, enum iommu_dev_features feat)
+{
+ return false;
+}
+
+static inline bool
+iommu_dev_feature_enabled(struct device *dev, enum iommu_dev_features feat)
+{
+ return false;
+}
+
+static inline int
+iommu_dev_enable_feature(struct device *dev, enum iommu_dev_features feat)
+{
+ return -ENODEV;
+}
+
+static inline int
+iommu_dev_disable_feature(struct device *dev, enum iommu_dev_features feat)
+{
+ return -ENODEV;
+}
+
+static inline int
+iommu_aux_attach_device(struct iommu_domain *domain, struct device *dev)
+{
+ return -ENODEV;
+}
+
+static inline void
+iommu_aux_detach_device(struct iommu_domain *domain, struct device *dev)
+{
+}
+
+static inline int
+iommu_aux_get_pasid(struct iommu_domain *domain, struct device *dev)
+{
+ return -ENODEV;
+}
+
#endif /* CONFIG_IOMMU_API */
#ifdef CONFIG_IOMMU_DEBUGFS
--
2.17.1