[PATCH 1/2] s390x/pci: add support for guests that request direct mapping

[Matthew Rosato]

When receiving a guest mpcifc(4) or mpcifc(6) instruction without the T
bit set, treat this as a request to perform direct mapping instead of
address translation.  In order to facilitiate this, pin the entirety of
guest memory into the host iommu.

Subsequent guest DMA operations are all expected to be of the format
guest_phys+sdma, allowing them to be used as lookup into the host
iommu table.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
---
 hw/s390x/s390-pci-bus.c         | 23 ++++++++++++++++++
 hw/s390x/s390-pci-inst.c        | 42 +++++++++++++++++++++++++++++++--
 include/hw/s390x/s390-pci-bus.h |  2 ++
 3 files changed, 65 insertions(+), 2 deletions(-)

diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
index 40b2567aa7..8d4224e032 100644
--- a/hw/s390x/s390-pci-bus.c
+++ b/hw/s390x/s390-pci-bus.c
@@ -18,6 +18,7 @@
 #include "hw/s390x/s390-pci-inst.h"
 #include "hw/s390x/s390-pci-kvm.h"
 #include "hw/s390x/s390-pci-vfio.h"
+#include "hw/boards.h"
 #include "hw/pci/pci_bus.h"
 #include "hw/qdev-properties.h"
 #include "hw/pci/pci_bridge.h"
@@ -720,6 +721,27 @@ void s390_pci_iommu_enable(S390PCIIOMMU *iommu)
                              TYPE_S390_IOMMU_MEMORY_REGION, OBJECT(&iommu->mr),
                              name, iommu->pal + 1);
     iommu->enabled = true;
+    iommu->direct_map = false;
+    memory_region_add_subregion(&iommu->mr, 0, 
MEMORY_REGION(&iommu->iommu_mr));
+    g_free(name);
+}
+
+void s390_pci_iommu_dm_enable(S390PCIIOMMU *iommu)
+{
+    MachineState *ms = MACHINE(qdev_get_machine());
+
+    /*
+     * For direct-mapping we must map the entire guest address space.  Because
+     * the mappings are contiguous we are not restricted to individual 4K
+     * mappings via vfio, so let's not worry about the DMA limit when
+     * calculating the range.
+     */
+    char *name = g_strdup_printf("iommu-s390-%04x", iommu->pbdev->uid);
+    memory_region_init_iommu(&iommu->iommu_mr, sizeof(iommu->iommu_mr),
+                             TYPE_S390_IOMMU_MEMORY_REGION, OBJECT(&iommu->mr),
+                             name, iommu->pba + ms->ram_size);
+    iommu->enabled = true;
+    iommu->direct_map = true;
     memory_region_add_subregion(&iommu->mr, 0, 
MEMORY_REGION(&iommu->iommu_mr));
     g_free(name);
 }
@@ -727,6 +749,7 @@ void s390_pci_iommu_enable(S390PCIIOMMU *iommu)
 void s390_pci_iommu_disable(S390PCIIOMMU *iommu)
 {
     iommu->enabled = false;
+    iommu->direct_map = false;
     g_hash_table_remove_all(iommu->iotlb);
     memory_region_del_subregion(&iommu->mr, MEMORY_REGION(&iommu->iommu_mr));
     object_unparent(OBJECT(&iommu->iommu_mr));
diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c
index 41655082da..f4d8fe8fe8 100644
--- a/hw/s390x/s390-pci-inst.c
+++ b/hw/s390x/s390-pci-inst.c
@@ -16,6 +16,7 @@
 #include "exec/memory.h"
 #include "qemu/error-report.h"
 #include "sysemu/hw_accel.h"
+#include "hw/boards.h"
 #include "hw/pci/pci_device.h"
 #include "hw/s390x/s390-pci-inst.h"
 #include "hw/s390x/s390-pci-bus.h"
@@ -990,6 +991,33 @@ int pci_dereg_irqs(S390PCIBusDevice *pbdev)
     return 0;
 }
 
+static void s390_pci_setup_stage2_map(S390PCIIOMMU *iommu)
+{
+    MachineState *ms = MACHINE(qdev_get_machine());
+    uint64_t remain = ms->ram_size, start = iommu->pba, mask, size, curr = 0;
+    uint64_t end = start + remain - 1;
+    IOMMUTLBEvent event = {
+        .type = IOMMU_NOTIFIER_MAP,
+        .entry = {
+            .target_as = &address_space_memory,
+            .translated_addr = 0,
+            .perm = IOMMU_RW,
+        },
+    };
+
+    while (remain >= TARGET_PAGE_SIZE) {
+        mask = dma_aligned_pow2_mask(start, end, 64);
+        size = mask + 1;
+        event.entry.iova = start;
+        event.entry.addr_mask = mask;
+        event.entry.translated_addr = curr;
+        memory_region_notify_iommu(&iommu->iommu_mr, 0, event);
+        start += size;
+        curr += size;
+        remain -= size;
+    }
+}
+
 static int reg_ioat(CPUS390XState *env, S390PCIBusDevice *pbdev, ZpciFib fib,
                     uintptr_t ra)
 {
@@ -1008,7 +1036,7 @@ static int reg_ioat(CPUS390XState *env, S390PCIBusDevice 
*pbdev, ZpciFib fib,
     }
 
     /* currently we only support designation type 1 with translation */
-    if (!(dt == ZPCI_IOTA_RTTO && t)) {
+    if (t && !(dt == ZPCI_IOTA_RTTO)) {
         error_report("unsupported ioat dt %d t %d", dt, t);
         s390_program_interrupt(env, PGM_OPERAND, ra);
         return -EINVAL;
@@ -1018,13 +1046,23 @@ static int reg_ioat(CPUS390XState *env, 
S390PCIBusDevice *pbdev, ZpciFib fib,
     iommu->pal = pal;
     iommu->g_iota = g_iota;
 
-    s390_pci_iommu_enable(iommu);
+    if (t) {
+        s390_pci_iommu_enable(iommu);
+    } else {
+        s390_pci_iommu_dm_enable(iommu);
+        /* If not translating, map everything now */
+        s390_pci_setup_stage2_map(iommu);
+    }
 
     return 0;
 }
 
 void pci_dereg_ioat(S390PCIIOMMU *iommu)
 {
+    MachineState *ms = MACHINE(qdev_get_machine());
+    if (iommu->direct_map) {
+        s390_pci_batch_unmap(iommu, iommu->pba, ms->ram_size);
+    }
     s390_pci_iommu_disable(iommu);
     iommu->pba = 0;
     iommu->pal = 0;
diff --git a/include/hw/s390x/s390-pci-bus.h b/include/hw/s390x/s390-pci-bus.h
index 2c43ea123f..2aa55e3fd0 100644
--- a/include/hw/s390x/s390-pci-bus.h
+++ b/include/hw/s390x/s390-pci-bus.h
@@ -278,6 +278,7 @@ struct S390PCIIOMMU {
     MemoryRegion mr;
     IOMMUMemoryRegion iommu_mr;
     bool enabled;
+    bool direct_map;
     uint64_t g_iota;
     uint64_t pba;
     uint64_t pal;
@@ -389,6 +390,7 @@ int pci_chsc_sei_nt2_have_event(void);
 void s390_pci_sclp_configure(SCCB *sccb);
 void s390_pci_sclp_deconfigure(SCCB *sccb);
 void s390_pci_iommu_enable(S390PCIIOMMU *iommu);
+void s390_pci_iommu_dm_enable(S390PCIIOMMU *iommu);
 void s390_pci_iommu_disable(S390PCIIOMMU *iommu);
 void s390_pci_generate_error_event(uint16_t pec, uint32_t fh, uint32_t fid,
                                    uint64_t faddr, uint32_t e);
-- 
2.47.0