spapr_pci: Add a 64-bit MMIO window

On real hardware, and under pHyp, the PCI host bridges on Power machines
typically advertise two outbound MMIO windows from the guest's physical
memory space to PCI memory space:
  - A 32-bit window which maps onto 2GiB..4GiB in the PCI address space
  - A 64-bit window which maps onto a large region somewhere high in PCI
    address space (traditionally this used an identity mapping from guest
    physical address to PCI address, but that's not always the case)

The qemu implementation in spapr-pci-host-bridge, however, only supports a
single outbound MMIO window, however.  At least some Linux versions expect
the two windows however, so we arranged this window to map onto the PCI
memory space from 2 GiB..~64 GiB, then advertised it as two contiguous
windows, the "32-bit" window from 2G..4G and the "64-bit" window from
4G..~64G.

This approach means, however, that the 64G window is not naturally aligned.
In turn this limits the size of the largest BAR we can map (which does have
to be naturally aligned) to roughly half of the total window.  With some
large nVidia GPGPU cards which have huge memory BARs, this is starting to
be a problem.

This patch adds true support for separate 32-bit and 64-bit outbound MMIO
windows to the spapr-pci-host-bridge implementation, each of which can
be independently configured.  The 32-bit window always maps to 2G.. in PCI
space, but the PCI address of the 64-bit window can be configured (it
defaults to the same as the guest physical address).

So as not to break possible existing configurations, as long as a 64-bit
window is not specified, a large single window can be specified.  This
will appear the same way to the guest as the old approach, although it's
now implemented by two contiguous memory regions rather than a single one.

For now, this only adds the possibility of 64-bit windows.  The default
configuration still uses the legacy mode.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>

2 files changed, 64 insertions, 16 deletions

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index d747e586c1..ea5d0e66f8 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -2371,7 +2371,8 @@ static HotpluggableCPUList *spapr_query_hotpluggable_cpus(MachineState *machine)
 }
 
 static void spapr_phb_placement(sPAPRMachineState *spapr, uint32_t index,
-                                uint64_t *buid, hwaddr *pio, hwaddr *mmio,
+                                uint64_t *buid, hwaddr *pio,
+                                hwaddr *mmio32, hwaddr *mmio64,
                                 unsigned n_dma, uint32_t *liobns, Error **errp)
 {
     const uint64_t base_buid = 0x800000020000000ULL;
@@ -2409,7 +2410,12 @@ static void spapr_phb_placement(sPAPRMachineState *spapr, uint32_t index,
 
     phb_base = phb0_base + index * phb_spacing;
     *pio = phb_base + pio_offset;
-    *mmio = phb_base + mmio_offset;
+    *mmio32 = phb_base + mmio_offset;
+    /*
+     * We don't set the 64-bit MMIO window, relying on the PHB's
+     * fallback behaviour of automatically splitting a large "32-bit"
+     * window into contiguous 32-bit and 64-bit windows
+     */
 }
 
 static void spapr_machine_class_init(ObjectClass *oc, void *data)
diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
index 8bd7f598a0..10d5de2d70 100644
--- a/hw/ppc/spapr_pci.c
+++ b/hw/ppc/spapr_pci.c
@@ -1317,14 +1317,16 @@ static void spapr_phb_realize(DeviceState *dev, Error **errp)
         if ((sphb->buid != (uint64_t)-1) || (sphb->dma_liobn[0] != (uint32_t)-1)
             || (sphb->dma_liobn[1] != (uint32_t)-1 && windows_supported == 2)
             || (sphb->mem_win_addr != (hwaddr)-1)
+            || (sphb->mem64_win_addr != (hwaddr)-1)
             || (sphb->io_win_addr != (hwaddr)-1)) {
             error_setg(errp, "Either \"index\" or other parameters must"
                        " be specified for PAPR PHB, not both");
             return;
         }
 
-        smc->phb_placement(spapr, sphb->index, &sphb->buid,
-                           &sphb->io_win_addr, &sphb->mem_win_addr,
+        smc->phb_placement(spapr, sphb->index,
+                           &sphb->buid, &sphb->io_win_addr,
+                           &sphb->mem_win_addr, &sphb->mem64_win_addr,
                            windows_supported, sphb->dma_liobn, &local_err);
         if (local_err) {
             error_propagate(errp, local_err);
@@ -1353,6 +1355,38 @@ static void spapr_phb_realize(DeviceState *dev, Error **errp)
         return;
     }
 
+    if (sphb->mem64_win_size != 0) {
+        if (sphb->mem64_win_addr == (hwaddr)-1) {
+            error_setg(errp,
+                       "64-bit memory window address not specified for PHB");
+            return;
+        }
+
+        if (sphb->mem_win_size > SPAPR_PCI_MEM32_WIN_SIZE) {
+            error_setg(errp, "32-bit memory window of size 0x%"HWADDR_PRIx
+                       " (max 2 GiB)", sphb->mem_win_size);
+            return;
+        }
+
+        if (sphb->mem64_win_pciaddr == (hwaddr)-1) {
+            /* 64-bit window defaults to identity mapping */
+            sphb->mem64_win_pciaddr = sphb->mem64_win_addr;
+        }
+    } else if (sphb->mem_win_size > SPAPR_PCI_MEM32_WIN_SIZE) {
+        /*
+         * For compatibility with old configuration, if no 64-bit MMIO
+         * window is specified, but the ordinary (32-bit) memory
+         * window is specified as > 2GiB, we treat it as a 2GiB 32-bit
+         * window, with a 64-bit MMIO window following on immediately
+         * afterwards
+         */
+        sphb->mem64_win_size = sphb->mem_win_size - SPAPR_PCI_MEM32_WIN_SIZE;
+        sphb->mem64_win_addr = sphb->mem_win_addr + SPAPR_PCI_MEM32_WIN_SIZE;
+        sphb->mem64_win_pciaddr =
+            SPAPR_PCI_MEM_WIN_BUS_OFFSET + SPAPR_PCI_MEM32_WIN_SIZE;
+        sphb->mem_win_size = SPAPR_PCI_MEM32_WIN_SIZE;
+    }
+
     if (spapr_pci_find_phb(spapr, sphb->buid)) {
         error_setg(errp, "PCI host bridges must have unique BUIDs");
         return;
@@ -1366,12 +1400,19 @@ static void spapr_phb_realize(DeviceState *dev, Error **errp)
     sprintf(namebuf, "%s.mmio", sphb->dtbusname);
     memory_region_init(&sphb->memspace, OBJECT(sphb), namebuf, UINT64_MAX);
 
-    sprintf(namebuf, "%s.mmio-alias", sphb->dtbusname);
-    memory_region_init_alias(&sphb->memwindow, OBJECT(sphb),
+    sprintf(namebuf, "%s.mmio32-alias", sphb->dtbusname);
+    memory_region_init_alias(&sphb->mem32window, OBJECT(sphb),
                              namebuf, &sphb->memspace,
                              SPAPR_PCI_MEM_WIN_BUS_OFFSET, sphb->mem_win_size);
     memory_region_add_subregion(get_system_memory(), sphb->mem_win_addr,
-                                &sphb->memwindow);
+                                &sphb->mem32window);
+
+    sprintf(namebuf, "%s.mmio64-alias", sphb->dtbusname);
+    memory_region_init_alias(&sphb->mem64window, OBJECT(sphb),
+                             namebuf, &sphb->memspace,
+                             sphb->mem64_win_pciaddr, sphb->mem64_win_size);
+    memory_region_add_subregion(get_system_memory(), sphb->mem64_win_addr,
+                                &sphb->mem64window);
 
     /* Initialize IO regions */
     sprintf(namebuf, "%s.io", sphb->dtbusname);
@@ -1524,6 +1565,10 @@ static Property spapr_phb_properties[] = {
     DEFINE_PROP_UINT64("mem_win_addr", sPAPRPHBState, mem_win_addr, -1),
     DEFINE_PROP_UINT64("mem_win_size", sPAPRPHBState, mem_win_size,
                        SPAPR_PCI_MMIO_WIN_SIZE),
+    DEFINE_PROP_UINT64("mem64_win_addr", sPAPRPHBState, mem64_win_addr, -1),
+    DEFINE_PROP_UINT64("mem64_win_size", sPAPRPHBState, mem64_win_size, 0),
+    DEFINE_PROP_UINT64("mem64_win_pciaddr", sPAPRPHBState, mem64_win_pciaddr,
+                       -1),
     DEFINE_PROP_UINT64("io_win_addr", sPAPRPHBState, io_win_addr, -1),
     DEFINE_PROP_UINT64("io_win_size", sPAPRPHBState, io_win_size,
                        SPAPR_PCI_IO_WIN_SIZE),
@@ -1759,10 +1804,6 @@ int spapr_populate_pci_dt(sPAPRPHBState *phb,
     int bus_off, i, j, ret;
     char nodename[FDT_NAME_MAX];
     uint32_t bus_range[] = { cpu_to_be32(0), cpu_to_be32(0xff) };
-    const uint64_t mmiosize = memory_region_size(&phb->memwindow);
-    const uint64_t w32max = (1ULL << 32) - SPAPR_PCI_MEM_WIN_BUS_OFFSET;
-    const uint64_t w32size = MIN(w32max, mmiosize);
-    const uint64_t w64size = (mmiosize > w32size) ? (mmiosize - w32size) : 0;
     struct {
         uint32_t hi;
         uint64_t child;
@@ -1777,15 +1818,16 @@ int spapr_populate_pci_dt(sPAPRPHBState *phb,
         {
             cpu_to_be32(b_ss(2)), cpu_to_be64(SPAPR_PCI_MEM_WIN_BUS_OFFSET),
             cpu_to_be64(phb->mem_win_addr),
-            cpu_to_be64(w32size),
+            cpu_to_be64(phb->mem_win_size),
         },
         {
-            cpu_to_be32(b_ss(3)), cpu_to_be64(1ULL << 32),
-            cpu_to_be64(phb->mem_win_addr + w32size),
-            cpu_to_be64(w64size)
+            cpu_to_be32(b_ss(3)), cpu_to_be64(phb->mem64_win_pciaddr),
+            cpu_to_be64(phb->mem64_win_addr),
+            cpu_to_be64(phb->mem64_win_size),
         },
     };
-    const unsigned sizeof_ranges = (w64size ? 3 : 2) * sizeof(ranges[0]);
+    const unsigned sizeof_ranges =
+        (phb->mem64_win_size ? 3 : 2) * sizeof(ranges[0]);
     uint64_t bus_reg[] = { cpu_to_be64(phb->buid), 0 };
     uint32_t interrupt_map_mask[] = {
         cpu_to_be32(b_ddddd(-1)|b_fff(0)), 0x0, 0x0, cpu_to_be32(-1)};