[PATCH v12 8/8] iommu/vt-d: Add custom allocator for IOASID

Jacob Pan
2020-04-21T18:47:04Z

When VT-d driver runs in the guest, PASID allocation must be
performed via virtual command interface. This patch registers a
custom IOASID allocator which takes precedence over the default
XArray based allocator. The resulting IOASID allocation will always
come from the host. This ensures that PASID namespace is system-
wide.

Virtual command registers are used in the guest only, to prevent
vmexit cost, we cache the capability and store it during initialization.

---
v12 - squashed virtual command register caching patch with its user
- reduce indentation
---

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Liu, Yi L <yi.l.liu@intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
---
drivers/iommu/dmar.c | 1 +
drivers/iommu/intel-iommu.c | 85 +++++++++++++++++++++++++++++++++++++++++++++
include/linux/intel-iommu.h | 7 ++++
3 files changed, 93 insertions(+)

diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
index a2b64f5f0372..d9dc787feef7 100644
--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -963,6 +963,7 @@ static int map_iommu(struct intel_iommu *iommu, u64 phys_addr)
warn_invalid_dmar(phys_addr, " returns all ones");
goto unmap;
}
+ iommu->vccap = dmar_readq(iommu->reg + DMAR_VCCAP_REG);

/* the registers might be more than one page */
map_size = max_t(int, ecap_max_iotlb_offset(iommu->ecap),
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 24de233faaf5..771dba33f402 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -1732,6 +1732,9 @@ static void free_dmar_iommu(struct intel_iommu *iommu)
if (ecap_prs(iommu->ecap))
intel_svm_finish_prq(iommu);
}
+ if (ecap_vcs(iommu->ecap) && vccap_pasid(iommu->vccap))
+ ioasid_unregister_allocator(&iommu->pasid_allocator);
+
#endif
}

@@ -3266,6 +3269,85 @@ static int copy_translation_tables(struct intel_iommu *iommu)
return ret;
}

+#ifdef CONFIG_INTEL_IOMMU_SVM
+static ioasid_t intel_vcmd_ioasid_alloc(ioasid_t min, ioasid_t max, void *data)
+{
+ struct intel_iommu *iommu = data;
+ ioasid_t ioasid;
+
+ if (!iommu)
+ return INVALID_IOASID;
+ /*
+ * VT-d virtual command interface always uses the full 20 bit
+ * PASID range. Host can partition guest PASID range based on
+ * policies but it is out of guest's control.
+ */
+ if (min < PASID_MIN || max > intel_pasid_max_id)
+ return INVALID_IOASID;
+
+ if (vcmd_alloc_pasid(iommu, &ioasid))
+ return INVALID_IOASID;
+
+ return ioasid;
+}
+
+static void intel_vcmd_ioasid_free(ioasid_t ioasid, void *data)
+{
+ struct intel_iommu *iommu = data;
+
+ if (!iommu)
+ return;
+ /*
+ * Sanity check the ioasid owner is done at upper layer, e.g. VFIO
+ * We can only free the PASID when all the devices are unbound.
+ */
+ if (ioasid_find(NULL, ioasid, NULL)) {
+ pr_alert("Cannot free active IOASID %d\n", ioasid);
+ return;
+ }
+ vcmd_free_pasid(iommu, ioasid);
+}
+
+static void register_pasid_allocator(struct intel_iommu *iommu)
+{
+ /*
+ * If we are running in the host, no need for custom allocator
+ * in that PASIDs are allocated from the host system-wide.
+ */
+ if (!cap_caching_mode(iommu->cap))
+ return;
+
+ if (!sm_supported(iommu)) {
+ pr_warn("VT-d Scalable Mode not enabled, no PASID allocation\n");
+ return;
+ }
+
+ /*
+ * Register a custom PASID allocator if we are running in a guest,
+ * guest PASID must be obtained via virtual command interface.
+ * There can be multiple vIOMMUs in each guest but only one allocator
+ * is active. All vIOMMU allocators will eventually be calling the same
+ * host allocator.
+ */
+ if (!ecap_vcs(iommu->ecap) || !vccap_pasid(iommu->vccap))
+ return;
+
+ pr_info("Register custom PASID allocator\n");
+ iommu->pasid_allocator.alloc = intel_vcmd_ioasid_alloc;
+ iommu->pasid_allocator.free = intel_vcmd_ioasid_free;
+ iommu->pasid_allocator.pdata = (void *)iommu;
+ if (ioasid_register_allocator(&iommu->pasid_allocator)) {
+ pr_warn("Custom PASID allocator failed, scalable mode disabled\n");
+ /*
+ * Disable scalable mode on this IOMMU if there
+ * is no custom allocator. Mixing SM capable vIOMMU
+ * and non-SM vIOMMU are not supported.
+ */
+ intel_iommu_sm = 0;
+ }
+}
+#endif
+
static int __init init_dmars(void)
{
struct dmar_drhd_unit *drhd;
@@ -3383,6 +3465,9 @@ static int __init init_dmars(void)
*/
for_each_active_iommu(iommu, drhd) {
iommu_flush_write_buffer(iommu);
+#ifdef CONFIG_INTEL_IOMMU_SVM
+ register_pasid_allocator(iommu);
+#endif
iommu_set_root_entry(iommu);
iommu->flush.flush_context(iommu, 0, 0, 0, DMA_CCMD_GLOBAL_INVL);
iommu->flush.flush_iotlb(iommu, 0, 0, 0, DMA_TLB_GLOBAL_FLUSH);
diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
index 1af16c6d3aec..cfac363bb2c7 100644
--- a/include/linux/intel-iommu.h
+++ b/include/linux/intel-iommu.h
@@ -19,6 +19,7 @@
#include <linux/iommu.h>
#include <linux/io-64-nonatomic-lo-hi.h>
#include <linux/dmar.h>
+#include <linux/ioasid.h>

#include <asm/cacheflush.h>
#include <asm/iommu.h>
@@ -195,6 +196,9 @@
#define ecap_max_handle_mask(e) ((e >> 20) & 0xf)
#define ecap_sc_support(e) ((e >> 7) & 0x1) /* Snooping Control */

+/* Virtual command interface capability */
+#define vccap_pasid(v) (((v) & DMA_VCS_PAS)) /* PASID allocation */
+
/* IOTLB_REG */
#define DMA_TLB_FLUSH_GRANU_OFFSET 60
#define DMA_TLB_GLOBAL_FLUSH (((u64)1) << 60)
@@ -288,6 +292,7 @@

/* PRS_REG */
#define DMA_PRS_PPR ((u32)1)
+#define DMA_VCS_PAS ((u64)1)

#define IOMMU_WAIT_OP(iommu, offset, op, cond, sts) \
do { \
@@ -563,6 +568,7 @@ struct intel_iommu {
u64 reg_size; /* size of hw register set */
u64 cap;
u64 ecap;
+ u64 vccap;
u32 gcmd; /* Holds TE, EAFL. Don't need SRTP, SFL, WBF */
raw_spinlock_t register_lock; /* protect register handling */
int seq_id; /* sequence id of the iommu */
@@ -583,6 +589,7 @@ struct intel_iommu {
#ifdef CONFIG_INTEL_IOMMU_SVM
struct page_req_dsc *prq;
unsigned char prq_name[16]; /* Name for PRQ interrupt */
+ struct ioasid_allocator_ops pasid_allocator; /* Custom allocator for PASIDs */
#endif
struct q_inval *qi; /* Queued invalidation info */
u32 *iommu_state; /* Store iommu states between suspend and resume.*/