[Qemu-devel] [PATCH v3 10/12] intel_iommu: support passthrough (PT)

[Peter Xu]

Hardware support for VT-d device passthrough. Although current Linux can
live with iommu=pt even without this, but this is faster than when using
software passthrough.

Signed-off-by: Peter Xu <address@hidden>
---
 hw/i386/intel_iommu.c          | 210 ++++++++++++++++++++++++++++++++---------
 hw/i386/intel_iommu_internal.h |   1 +
 hw/i386/trace-events           |   2 +
 hw/i386/x86-iommu.c            |   1 +
 include/hw/i386/x86-iommu.h    |   1 +
 5 files changed, 171 insertions(+), 44 deletions(-)

diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index 1a7eba2..1d034f9 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -640,6 +640,29 @@ static bool vtd_slpte_nonzero_rsvd(uint64_t slpte, 
uint32_t level)
     }
 }
 
+/* Find the VTD address space associated with a given bus number */
+static VTDBus *vtd_find_as_from_bus_num(IntelIOMMUState *s, uint8_t bus_num)
+{
+    VTDBus *vtd_bus = s->vtd_as_by_bus_num[bus_num];
+    if (!vtd_bus) {
+        /*
+         * Iterate over the registered buses to find the one which
+         * currently hold this bus number, and update the bus_num
+         * lookup table:
+         */
+        GHashTableIter iter;
+
+        g_hash_table_iter_init(&iter, s->vtd_as_by_busptr);
+        while (g_hash_table_iter_next (&iter, NULL, (void**)&vtd_bus)) {
+            if (pci_bus_num(vtd_bus->bus) == bus_num) {
+                s->vtd_as_by_bus_num[bus_num] = vtd_bus;
+                return vtd_bus;
+            }
+        }
+    }
+    return vtd_bus;
+}
+
 /* Given the @iova, get relevant @slptep. @slpte_level will be the last level
  * of the translation, can be used for deciding the size of large page.
  */
@@ -881,6 +904,11 @@ static int vtd_dev_to_context_entry(IntelIOMMUState *s, 
uint8_t bus_num,
                 type_fail = true;
             }
             break;
+        case VTD_CONTEXT_TT_PASS_THROUGH:
+            if (!x86_iommu->pt_supported) {
+                type_fail = true;
+            }
+            break;
         default:
             /* Unknwon type */
             type_fail = true;
@@ -894,6 +922,84 @@ static int vtd_dev_to_context_entry(IntelIOMMUState *s, 
uint8_t bus_num,
     return 0;
 }
 
+/*
+ * Fetch translation type for specific device. Returns <0 if error
+ * happens, otherwise return the shifted type to check against
+ * VTD_CONTEXT_TT_*.
+ */
+static int vtd_dev_get_trans_type(VTDAddressSpace *as)
+{
+    IntelIOMMUState *s;
+    VTDContextEntry ce;
+    int ret;
+
+    s = as->iommu_state;
+
+    ret = vtd_dev_to_context_entry(s, pci_bus_num(as->bus),
+                                   as->devfn, &ce);
+    if (ret) {
+        return ret;
+    }
+
+    return vtd_ce_get_type(&ce);
+}
+
+static bool vtd_dev_pt_enabled(VTDAddressSpace *as)
+{
+    int ret;
+
+    assert(as);
+
+    ret = vtd_dev_get_trans_type(as);
+    if (ret < 0) {
+        /*
+         * Possibly failed to parse the context entry for some reason
+         * (e.g., during init, or any guest configuration errors on
+         * context entries). We should assume PT not enabled for
+         * safety.
+         */
+        return false;
+    }
+
+    return ret == VTD_CONTEXT_TT_PASS_THROUGH;
+}
+
+/*
+ * When we are during init phase (device realizations, global
+ * enable/disable of translations), we should not detect PT
+ * (passthrough) when switching address spaces. In that cases, we
+ * should set `detect_pt' to false.
+ *
+ * Return whether the device is using IOMMU translation.
+ */
+static bool vtd_switch_address_space(VTDAddressSpace *as, bool detect_pt)
+{
+    bool use_iommu;
+
+    assert(as);
+
+    use_iommu = as->iommu_state->dmar_enabled;
+    if (detect_pt) {
+        use_iommu &= !vtd_dev_pt_enabled(as);
+    }
+
+    trace_vtd_switch_address_space(pci_bus_num(as->bus),
+                                   VTD_PCI_SLOT(as->devfn),
+                                   VTD_PCI_FUNC(as->devfn),
+                                   use_iommu);
+
+    /* Turn off first then on the other */
+    if (use_iommu) {
+        memory_region_set_enabled(&as->sys_alias, false);
+        memory_region_set_enabled(&as->iommu, true);
+    } else {
+        memory_region_set_enabled(&as->iommu, false);
+        memory_region_set_enabled(&as->sys_alias, true);
+    }
+
+    return use_iommu;
+}
+
 static inline uint16_t vtd_make_source_id(uint8_t bus_num, uint8_t devfn)
 {
     return ((bus_num & 0xffUL) << 8) | (devfn & 0xffUL);
@@ -931,6 +1037,31 @@ static inline bool vtd_is_interrupt_addr(hwaddr addr)
     return VTD_INTERRUPT_ADDR_FIRST <= addr && addr <= VTD_INTERRUPT_ADDR_LAST;
 }
 
+static void vtd_pt_enable_fast_path(IntelIOMMUState *s, uint16_t source_id)
+{
+    VTDBus *vtd_bus;
+    VTDAddressSpace *vtd_as;
+    const char *msg = "FAIL";
+
+    vtd_bus = vtd_find_as_from_bus_num(s, VTD_SID_TO_BUS(source_id));
+    if (!vtd_bus) {
+        goto out;
+    }
+
+    vtd_as = vtd_bus->dev_as[VTD_SID_TO_DEVFN(source_id)];
+    if (!vtd_as) {
+        goto out;
+    }
+
+    if (vtd_switch_address_space(vtd_as, true) == false) {
+        /* We switched off IOMMU region successfully. */
+        msg = "SUCCESS";
+    }
+
+out:
+    trace_vtd_pt_enable_fast_path(source_id, msg);
+}
+
 /* Map dev to context-entry then do a paging-structures walk to do a iommu
  * translation.
  *
@@ -1002,6 +1133,30 @@ static void vtd_do_iommu_translate(VTDAddressSpace 
*vtd_as, PCIBus *bus,
         cc_entry->context_cache_gen = s->context_cache_gen;
     }
 
+    /*
+     * We don't need to translate for pass-through context entries.
+     * Also, let's ignore IOTLB caching as well for PT devices.
+     */
+    if (vtd_ce_get_type(&ce) == VTD_CONTEXT_TT_PASS_THROUGH) {
+        entry->translated_addr = entry->iova;
+        entry->addr_mask = VTD_PAGE_SIZE - 1;
+        entry->perm = IOMMU_RW;
+        trace_vtd_translate_pt(source_id, entry->iova);
+
+        /*
+         * When this happens, it means firstly caching-mode is not
+         * enabled, and this is the first passthrough translation for
+         * the device. Let's enable the fast path for passthrough.
+         *
+         * When passthrough is disabled again for the device, we can
+         * capture it via the context entry invalidation, then the
+         * IOMMU region can be swapped back.
+         */
+        vtd_pt_enable_fast_path(s, source_id);
+
+        return;
+    }
+
     ret_fr = vtd_iova_to_slpte(&ce, addr, is_write, &slpte, &level,
                                &reads, &writes);
     if (ret_fr) {
@@ -1081,29 +1236,6 @@ static void 
vtd_context_global_invalidate(IntelIOMMUState *s)
     vtd_iommu_replay_all(s);
 }
 
-
-/* Find the VTD address space currently associated with a given bus number,
- */
-static VTDBus *vtd_find_as_from_bus_num(IntelIOMMUState *s, uint8_t bus_num)
-{
-    VTDBus *vtd_bus = s->vtd_as_by_bus_num[bus_num];
-    if (!vtd_bus) {
-        /* Iterate over the registered buses to find the one
-         * which currently hold this bus number, and update the bus_num lookup 
table:
-         */
-        GHashTableIter iter;
-
-        g_hash_table_iter_init(&iter, s->vtd_as_by_busptr);
-        while (g_hash_table_iter_next (&iter, NULL, (void**)&vtd_bus)) {
-            if (pci_bus_num(vtd_bus->bus) == bus_num) {
-                s->vtd_as_by_bus_num[bus_num] = vtd_bus;
-                return vtd_bus;
-            }
-        }
-    }
-    return vtd_bus;
-}
-
 /* Do a context-cache device-selective invalidation.
  * @func_mask: FM field after shifting
  */
@@ -1146,6 +1278,11 @@ static void 
vtd_context_device_invalidate(IntelIOMMUState *s,
                                              VTD_PCI_FUNC(devfn_it));
                 vtd_as->context_cache_entry.context_cache_gen = 0;
                 /*
+                 * Do switch address space when needed, in case if the
+                 * device passthrough bit is switched.
+                 */
+                vtd_switch_address_space(vtd_as, true);
+                /*
                  * So a device is moving out of (or moving into) a
                  * domain, a replay() suites here to notify all the
                  * IOMMU_NOTIFIER_MAP registers about this change.
@@ -1377,25 +1514,6 @@ static void vtd_handle_gcmd_sirtp(IntelIOMMUState *s)
     vtd_set_clear_mask_long(s, DMAR_GSTS_REG, 0, VTD_GSTS_IRTPS);
 }
 
-static void vtd_switch_address_space(VTDAddressSpace *as)
-{
-    assert(as);
-
-    trace_vtd_switch_address_space(pci_bus_num(as->bus),
-                                   VTD_PCI_SLOT(as->devfn),
-                                   VTD_PCI_FUNC(as->devfn),
-                                   as->iommu_state->dmar_enabled);
-
-    /* Turn off first then on the other */
-    if (as->iommu_state->dmar_enabled) {
-        memory_region_set_enabled(&as->sys_alias, false);
-        memory_region_set_enabled(&as->iommu, true);
-    } else {
-        memory_region_set_enabled(&as->iommu, false);
-        memory_region_set_enabled(&as->sys_alias, true);
-    }
-}
-
 static void vtd_switch_address_space_all(IntelIOMMUState *s)
 {
     GHashTableIter iter;
@@ -1408,7 +1526,7 @@ static void vtd_switch_address_space_all(IntelIOMMUState 
*s)
             if (!vtd_bus->dev_as[i]) {
                 continue;
             }
-            vtd_switch_address_space(vtd_bus->dev_as[i]);
+            vtd_switch_address_space(vtd_bus->dev_as[i], false);
         }
     }
 }
@@ -2712,7 +2830,7 @@ VTDAddressSpace *vtd_find_add_as(IntelIOMMUState *s, 
PCIBus *bus, int devfn)
                                             &vtd_dev_as->sys_alias, 1);
         memory_region_add_subregion_overlap(&vtd_dev_as->root, 0,
                                             &vtd_dev_as->iommu, 1);
-        vtd_switch_address_space(vtd_dev_as);
+        vtd_switch_address_space(vtd_dev_as, false);
     }
     return vtd_dev_as;
 }
@@ -2860,6 +2978,10 @@ static void vtd_init(IntelIOMMUState *s)
         s->ecap |= VTD_ECAP_DT;
     }
 
+    if (x86_iommu->pt_supported) {
+        s->ecap |= VTD_ECAP_PT;
+    }
+
     if (s->caching_mode) {
         s->cap |= VTD_CAP_CM;
     }
diff --git a/hw/i386/intel_iommu_internal.h b/hw/i386/intel_iommu_internal.h
index 29d6707..0e73a65 100644
--- a/hw/i386/intel_iommu_internal.h
+++ b/hw/i386/intel_iommu_internal.h
@@ -187,6 +187,7 @@
 /* Interrupt Remapping support */
 #define VTD_ECAP_IR                 (1ULL << 3)
 #define VTD_ECAP_EIM                (1ULL << 4)
+#define VTD_ECAP_PT                 (1ULL << 6)
 #define VTD_ECAP_MHMV               (15ULL << 20)
 
 /* CAP_REG */
diff --git a/hw/i386/trace-events b/hw/i386/trace-events
index 04a6980..5c3e466 100644
--- a/hw/i386/trace-events
+++ b/hw/i386/trace-events
@@ -38,6 +38,8 @@ vtd_page_walk_skip_perm(uint64_t iova, uint64_t next) "Page 
walk skip iova 0x%"P
 vtd_page_walk_skip_reserve(uint64_t iova, uint64_t next) "Page walk skip iova 
0x%"PRIx64" - 0x%"PRIx64" due to rsrv set"
 vtd_switch_address_space(uint8_t bus, uint8_t slot, uint8_t fn, bool on) 
"Device %02x:%02x.%x switching address space (iommu enabled=%d)"
 vtd_as_unmap_whole(uint8_t bus, uint8_t slot, uint8_t fn, uint64_t iova, 
uint64_t size) "Device %02x:%02x.%x start 0x%"PRIx64" size 0x%"PRIx64
+vtd_translate_pt(uint16_t sid, uint64_t addr) "source id 0x%"PRIu16", iova 
0x%"PRIx64
+vtd_pt_enable_fast_path(uint16_t sid, const char *msg) "sid 0x%"PRIu16" %s"
 
 # hw/i386/amd_iommu.c
 amdvi_evntlog_fail(uint64_t addr, uint32_t head) "error: fail to write at addr 
0x%"PRIx64" +  offset 0x%"PRIx32
diff --git a/hw/i386/x86-iommu.c b/hw/i386/x86-iommu.c
index 02b8825..293caf8 100644
--- a/hw/i386/x86-iommu.c
+++ b/hw/i386/x86-iommu.c
@@ -91,6 +91,7 @@ static void x86_iommu_realize(DeviceState *dev, Error **errp)
 static Property x86_iommu_properties[] = {
     DEFINE_PROP_BOOL("intremap", X86IOMMUState, intr_supported, false),
     DEFINE_PROP_BOOL("device-iotlb", X86IOMMUState, dt_supported, false),
+    DEFINE_PROP_BOOL("pt", X86IOMMUState, pt_supported, true),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/include/hw/i386/x86-iommu.h b/include/hw/i386/x86-iommu.h
index 361c07c..ef89c0c 100644
--- a/include/hw/i386/x86-iommu.h
+++ b/include/hw/i386/x86-iommu.h
@@ -74,6 +74,7 @@ struct X86IOMMUState {
     SysBusDevice busdev;
     bool intr_supported;        /* Whether vIOMMU supports IR */
     bool dt_supported;          /* Whether vIOMMU supports DT */
+    bool pt_supported;          /* Whether vIOMMU supports pass-through */
     IommuType type;             /* IOMMU type - AMD/Intel     */
     QLIST_HEAD(, IEC_Notifier) iec_notifiers; /* IEC notify list */
 };
-- 
2.7.4