[PATCH v3 5/5] s390x/pci: Honor DMA limits set by vfio

[Matthew Rosato]

When an s390 guest is using lazy unmapping, it can result in a very
large number of oustanding DMA requests, far beyond the default
limit configured for vfio.  Let's track DMA usage similar to vfio
in the host, and trigger the guest to flush their DMA mappings
before vfio runs out.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
---
 hw/s390x/s390-pci-bus.c  | 56 +++++++++++++++++++++++++++++++++++++++++++-----
 hw/s390x/s390-pci-bus.h  |  9 ++++++++
 hw/s390x/s390-pci-inst.c | 34 +++++++++++++++++++++++------
 hw/s390x/s390-pci-inst.h |  3 +++
 4 files changed, 91 insertions(+), 11 deletions(-)

diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
index 92146a2..8e8398d 100644
--- a/hw/s390x/s390-pci-bus.c
+++ b/hw/s390x/s390-pci-bus.c
@@ -17,6 +17,7 @@
 #include "cpu.h"
 #include "s390-pci-bus.h"
 #include "s390-pci-inst.h"
+#include "s390-pci-vfio.h"
 #include "hw/pci/pci_bus.h"
 #include "hw/qdev-properties.h"
 #include "hw/pci/pci_bridge.h"
@@ -24,6 +25,8 @@
 #include "qemu/error-report.h"
 #include "qemu/module.h"
 
+#include "hw/vfio/pci.h"
+
 #ifndef DEBUG_S390PCI_BUS
 #define DEBUG_S390PCI_BUS  0
 #endif
@@ -737,6 +740,41 @@ static void s390_pci_iommu_free(S390pciState *s, PCIBus 
*bus, int32_t devfn)
     object_unref(OBJECT(iommu));
 }
 
+static S390PCIDMACount *s390_start_dma_count(S390pciState *s, VFIODevice *vdev)
+{
+    int id = vdev->group->container->fd;
+    S390PCIDMACount *cnt;
+    uint32_t avail;
+
+    if (!s390_pci_update_dma_avail(id, &avail)) {
+        return NULL;
+    }
+
+    QTAILQ_FOREACH(cnt, &s->zpci_dma_limit, link) {
+        if (cnt->id  == id) {
+            cnt->users++;
+            return cnt;
+        }
+    }
+
+    cnt = g_new0(S390PCIDMACount, 1);
+    cnt->id = id;
+    cnt->users = 1;
+    cnt->avail = avail;
+    QTAILQ_INSERT_TAIL(&s->zpci_dma_limit, cnt, link);
+    return cnt;
+}
+
+static void s390_end_dma_count(S390pciState *s, S390PCIDMACount *cnt)
+{
+    assert(cnt);
+
+    cnt->users--;
+    if (cnt->users == 0) {
+        QTAILQ_REMOVE(&s->zpci_dma_limit, cnt, link);
+    }
+}
+
 static void s390_pcihost_realize(DeviceState *dev, Error **errp)
 {
     PCIBus *b;
@@ -764,6 +802,7 @@ static void s390_pcihost_realize(DeviceState *dev, Error 
**errp)
     s->bus_no = 0;
     QTAILQ_INIT(&s->pending_sei);
     QTAILQ_INIT(&s->zpci_devs);
+    QTAILQ_INIT(&s->zpci_dma_limit);
 
     css_register_io_adapters(CSS_IO_ADAPTER_PCI, true, false,
                              S390_ADAPTER_SUPPRESSIBLE, errp);
@@ -902,6 +941,7 @@ static void s390_pcihost_plug(HotplugHandler *hotplug_dev, 
DeviceState *dev,
 {
     S390pciState *s = S390_PCI_HOST_BRIDGE(hotplug_dev);
     PCIDevice *pdev = NULL;
+    VFIOPCIDevice *vpdev = NULL;
     S390PCIBusDevice *pbdev = NULL;
 
     if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_BRIDGE)) {
@@ -941,17 +981,20 @@ static void s390_pcihost_plug(HotplugHandler 
*hotplug_dev, DeviceState *dev,
             }
         }
 
+        pbdev->pdev = pdev;
+        pbdev->iommu = s390_pci_get_iommu(s, pci_get_bus(pdev), pdev->devfn);
+        pbdev->iommu->pbdev = pbdev;
+        pbdev->state = ZPCI_FS_DISABLED;
+
         if (object_dynamic_cast(OBJECT(dev), "vfio-pci")) {
             pbdev->fh |= FH_SHM_VFIO;
+            vpdev = container_of(pbdev->pdev, VFIOPCIDevice, pdev);
+            pbdev->iommu->dma_limit = s390_start_dma_count(s,
+                                                           &vpdev->vbasedev);
         } else {
             pbdev->fh |= FH_SHM_EMUL;
         }
 
-        pbdev->pdev = pdev;
-        pbdev->iommu = s390_pci_get_iommu(s, pci_get_bus(pdev), pdev->devfn);
-        pbdev->iommu->pbdev = pbdev;
-        pbdev->state = ZPCI_FS_DISABLED;
-
         if (s390_pci_msix_init(pbdev)) {
             error_setg(errp, "MSI-X support is mandatory "
                        "in the S390 architecture");
@@ -1004,6 +1047,9 @@ static void s390_pcihost_unplug(HotplugHandler 
*hotplug_dev, DeviceState *dev,
         pbdev->fid = 0;
         QTAILQ_REMOVE(&s->zpci_devs, pbdev, link);
         g_hash_table_remove(s->zpci_table, &pbdev->idx);
+        if (pbdev->iommu->dma_limit) {
+            s390_end_dma_count(s, pbdev->iommu->dma_limit);
+        }
         qdev_unrealize(dev);
     }
 }
diff --git a/hw/s390x/s390-pci-bus.h b/hw/s390x/s390-pci-bus.h
index 0458059..f166fd9 100644
--- a/hw/s390x/s390-pci-bus.h
+++ b/hw/s390x/s390-pci-bus.h
@@ -270,6 +270,13 @@ typedef struct S390IOTLBEntry {
     uint64_t perm;
 } S390IOTLBEntry;
 
+typedef struct S390PCIDMACount {
+    int id;
+    int users;
+    uint32_t avail;
+    QTAILQ_ENTRY(S390PCIDMACount) link;
+} S390PCIDMACount;
+
 struct S390PCIIOMMU {
     Object parent_obj;
     S390PCIBusDevice *pbdev;
@@ -281,6 +288,7 @@ struct S390PCIIOMMU {
     uint64_t pba;
     uint64_t pal;
     GHashTable *iotlb;
+    S390PCIDMACount *dma_limit;
 };
 
 typedef struct S390PCIIOMMUTable {
@@ -356,6 +364,7 @@ struct S390pciState {
     GHashTable *zpci_table;
     QTAILQ_HEAD(, SeiContainer) pending_sei;
     QTAILQ_HEAD(, S390PCIBusDevice) zpci_devs;
+    QTAILQ_HEAD(, S390PCIDMACount) zpci_dma_limit;
 };
 
 S390pciState *s390_get_phb(void);
diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c
index 2f7a7d7..cc34b17 100644
--- a/hw/s390x/s390-pci-inst.c
+++ b/hw/s390x/s390-pci-inst.c
@@ -32,6 +32,9 @@
         }                                                          \
     } while (0)
 
+#define inc_dma_avail(iommu) if (iommu->dma_limit) iommu->dma_limit->avail++;
+#define dec_dma_avail(iommu) if (iommu->dma_limit) iommu->dma_limit->avail--;
+
 static void s390_set_status_code(CPUS390XState *env,
                                  uint8_t r, uint64_t status_code)
 {
@@ -572,7 +575,8 @@ int pcistg_service_call(S390CPU *cpu, uint8_t r1, uint8_t 
r2, uintptr_t ra)
     return 0;
 }
 
-static void s390_pci_update_iotlb(S390PCIIOMMU *iommu, S390IOTLBEntry *entry)
+static uint32_t s390_pci_update_iotlb(S390PCIIOMMU *iommu,
+                                      S390IOTLBEntry *entry)
 {
     S390IOTLBEntry *cache = g_hash_table_lookup(iommu->iotlb, &entry->iova);
     IOMMUTLBEntry notify = {
@@ -585,14 +589,15 @@ static void s390_pci_update_iotlb(S390PCIIOMMU *iommu, 
S390IOTLBEntry *entry)
 
     if (entry->perm == IOMMU_NONE) {
         if (!cache) {
-            return;
+            goto out;
         }
         g_hash_table_remove(iommu->iotlb, &entry->iova);
+        inc_dma_avail(iommu);
     } else {
         if (cache) {
             if (cache->perm == entry->perm &&
                 cache->translated_addr == entry->translated_addr) {
-                return;
+                goto out;
             }
 
             notify.perm = IOMMU_NONE;
@@ -606,9 +611,13 @@ static void s390_pci_update_iotlb(S390PCIIOMMU *iommu, 
S390IOTLBEntry *entry)
         cache->len = PAGE_SIZE;
         cache->perm = entry->perm;
         g_hash_table_replace(iommu->iotlb, &cache->iova, cache);
+        dec_dma_avail(iommu);
     }
 
     memory_region_notify_iommu(&iommu->iommu_mr, 0, notify);
+
+out:
+    return iommu->dma_limit ? iommu->dma_limit->avail : 1;
 }
 
 int rpcit_service_call(S390CPU *cpu, uint8_t r1, uint8_t r2, uintptr_t ra)
@@ -620,6 +629,7 @@ int rpcit_service_call(S390CPU *cpu, uint8_t r1, uint8_t 
r2, uintptr_t ra)
     S390PCIIOMMU *iommu;
     S390IOTLBEntry entry;
     hwaddr start, end;
+    uint32_t dma_avail;
 
     if (env->psw.mask & PSW_MASK_PSTATE) {
         s390_program_interrupt(env, PGM_PRIVILEGED, ra);
@@ -658,6 +668,11 @@ int rpcit_service_call(S390CPU *cpu, uint8_t r1, uint8_t 
r2, uintptr_t ra)
     }
 
     iommu = pbdev->iommu;
+    if (iommu->dma_limit) {
+        dma_avail = iommu->dma_limit->avail;
+    } else {
+        dma_avail = 1;
+    }
     if (!iommu->g_iota) {
         error = ERR_EVENT_INVALAS;
         goto err;
@@ -675,8 +690,9 @@ int rpcit_service_call(S390CPU *cpu, uint8_t r1, uint8_t 
r2, uintptr_t ra)
         }
 
         start += entry.len;
-        while (entry.iova < start && entry.iova < end) {
-            s390_pci_update_iotlb(iommu, &entry);
+        while (entry.iova < start && entry.iova < end &&
+               (dma_avail > 0 || entry.perm == IOMMU_NONE)) {
+            dma_avail = s390_pci_update_iotlb(iommu, &entry);
             entry.iova += PAGE_SIZE;
             entry.translated_addr += PAGE_SIZE;
         }
@@ -689,7 +705,13 @@ err:
         s390_pci_generate_error_event(error, pbdev->fh, pbdev->fid, start, 0);
     } else {
         pbdev->fmb.counter[ZPCI_FMB_CNT_RPCIT]++;
-        setcc(cpu, ZPCI_PCI_LS_OK);
+        if (dma_avail > 0) {
+            setcc(cpu, ZPCI_PCI_LS_OK);
+        } else {
+            /* vfio DMA mappings are exhausted, trigger a RPCIT */
+            setcc(cpu, ZPCI_PCI_LS_ERR);
+            s390_set_status_code(env, r1, ZPCI_RPCIT_ST_INSUFF_RES);
+        }
     }
     return 0;
 }
diff --git a/hw/s390x/s390-pci-inst.h b/hw/s390x/s390-pci-inst.h
index fa3bf8b..8ee3a3c 100644
--- a/hw/s390x/s390-pci-inst.h
+++ b/hw/s390x/s390-pci-inst.h
@@ -254,6 +254,9 @@ typedef struct ClpReqRspQueryPciGrp {
 #define ZPCI_STPCIFC_ST_INVAL_DMAAS   28
 #define ZPCI_STPCIFC_ST_ERROR_RECOVER 40
 
+/* Refresh PCI Translations status codes */
+#define ZPCI_RPCIT_ST_INSUFF_RES      16
+
 /* FIB function controls */
 #define ZPCI_FIB_FC_ENABLED     0x80
 #define ZPCI_FIB_FC_ERROR       0x40
-- 
1.8.3.1