spapr: Improved placement of PCI host bridges in guest memory map

Currently, the MMIO space for accessing PCI on pseries guests begins at
1 TiB in guest address space.  Each PCI host bridge (PHB) has a 64 GiB
chunk of address space in which it places its outbound PIO and 32-bit and
64-bit MMIO windows.

This scheme as several problems:
  - It limits guest RAM to 1 TiB (though we have a limited fix for this
    now)
  - It limits the total MMIO window to 64 GiB.  This is not always enough
    for some of the large nVidia GPGPU cards
  - Putting all the windows into a single 64 GiB area means that naturally
    aligning things within there will waste more address space.
In addition there was a miscalculation in some of the defaults, which meant
that the MMIO windows for each PHB actually slightly overran the 64 GiB
region for that PHB.  We got away without nasty consequences because
the overrun fit within an unused area at the beginning of the next PHB's
region, but it's not pretty.

This patch implements a new scheme which addresses those problems, and is
also closer to what bare metal hardware and pHyp guests generally use.

Because some guest versions (including most current distro kernels) can't
access PCI MMIO above 64 TiB, we put all the PCI windows between 32 TiB and
64 TiB.  This is broken into 1 TiB chunks.  The first 1 TiB contains the
PIO (64 kiB) and 32-bit MMIO (2 GiB) windows for all of the PHBs.  Each
subsequent TiB chunk contains a naturally aligned 64-bit MMIO window for
one PHB each.

This reduces the number of allowed PHBs (without full manual configuration
of all the windows) from 256 to 31, but this should still be plenty in
practice.

We also change some of the default window sizes for manually configured
PHBs to saner values.

Finally we adjust some tests and libqos so that it correctly uses the new
default locations.  Ideally it would parse the device tree given to the
guest, but that's a more complex problem for another time.

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

1 files changed, 92 insertions, 30 deletions

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index ea5d0e66f8..ddb7438434 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -2375,31 +2375,38 @@ static void spapr_phb_placement(sPAPRMachineState *spapr, uint32_t index,
                                 hwaddr *mmio32, hwaddr *mmio64,
                                 unsigned n_dma, uint32_t *liobns, Error **errp)
 {
+    /*
+     * New-style PHB window placement.
+     *
+     * Goals: Gives large (1TiB), naturally aligned 64-bit MMIO window
+     * for each PHB, in addition to 2GiB 32-bit MMIO and 64kiB PIO
+     * windows.
+     *
+     * Some guest kernels can't work with MMIO windows above 1<<46
+     * (64TiB), so we place up to 31 PHBs in the area 32TiB..64TiB
+     *
+     * 32TiB..(33TiB+1984kiB) contains the 64kiB PIO windows for each
+     * PHB stacked together.  (32TiB+2GiB)..(32TiB+64GiB) contains the
+     * 2GiB 32-bit MMIO windows for each PHB.  Then 33..64TiB has the
+     * 1TiB 64-bit MMIO windows for each PHB.
+     */
     const uint64_t base_buid = 0x800000020000000ULL;
-    const hwaddr phb_spacing = 0x1000000000ULL; /* 64 GiB */
-    const hwaddr mmio_offset = 0xa0000000; /* 2 GiB + 512 MiB */
-    const hwaddr pio_offset = 0x80000000; /* 2 GiB */
-    const uint32_t max_index = 255;
-    const hwaddr phb0_alignment = 0x10000000000ULL; /* 1 TiB */
-
-    uint64_t ram_top = MACHINE(spapr)->ram_size;
-    hwaddr phb0_base, phb_base;
+    const int max_phbs =
+        (SPAPR_PCI_LIMIT - SPAPR_PCI_BASE) / SPAPR_PCI_MEM64_WIN_SIZE - 1;
     int i;
 
-    /* Do we have hotpluggable memory? */
-    if (MACHINE(spapr)->maxram_size > ram_top) {
-        /* Can't just use maxram_size, because there may be an
-         * alignment gap between normal and hotpluggable memory
-         * regions */
-        ram_top = spapr->hotplug_memory.base +
-            memory_region_size(&spapr->hotplug_memory.mr);
-    }
-
-    phb0_base = QEMU_ALIGN_UP(ram_top, phb0_alignment);
+    /* Sanity check natural alignments */
+    QEMU_BUILD_BUG_ON((SPAPR_PCI_BASE % SPAPR_PCI_MEM64_WIN_SIZE) != 0);
+    QEMU_BUILD_BUG_ON((SPAPR_PCI_LIMIT % SPAPR_PCI_MEM64_WIN_SIZE) != 0);
+    QEMU_BUILD_BUG_ON((SPAPR_PCI_MEM64_WIN_SIZE % SPAPR_PCI_MEM32_WIN_SIZE) != 0);
+    QEMU_BUILD_BUG_ON((SPAPR_PCI_MEM32_WIN_SIZE % SPAPR_PCI_IO_WIN_SIZE) != 0);
+    /* Sanity check bounds */
+    QEMU_BUILD_BUG_ON((max_phbs * SPAPR_PCI_IO_WIN_SIZE) > SPAPR_PCI_MEM32_WIN_SIZE);
+    QEMU_BUILD_BUG_ON((max_phbs * SPAPR_PCI_MEM32_WIN_SIZE) > SPAPR_PCI_MEM64_WIN_SIZE);
 
-    if (index > max_index) {
+    if (index >= max_phbs) {
         error_setg(errp, "\"index\" for PAPR PHB is too large (max %u)",
-                   max_index);
+                   max_phbs - 1);
         return;
     }
 
@@ -2408,14 +2415,9 @@ static void spapr_phb_placement(sPAPRMachineState *spapr, uint32_t index,
         liobns[i] = SPAPR_PCI_LIOBN(index, i);
     }
 
-    phb_base = phb0_base + index * phb_spacing;
-    *pio = phb_base + pio_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
-     */
+    *pio = SPAPR_PCI_BASE + index * SPAPR_PCI_IO_WIN_SIZE;
+    *mmio32 = SPAPR_PCI_BASE + (index + 1) * SPAPR_PCI_MEM32_WIN_SIZE;
+    *mmio64 = SPAPR_PCI_BASE + (index + 1) * SPAPR_PCI_MEM64_WIN_SIZE;
 }
 
 static void spapr_machine_class_init(ObjectClass *oc, void *data)
@@ -2519,8 +2521,67 @@ DEFINE_SPAPR_MACHINE(2_8, "2.8", true);
 /*
  * pseries-2.7
  */
-#define SPAPR_COMPAT_2_7 \
-    HW_COMPAT_2_7 \
+#define SPAPR_COMPAT_2_7                            \
+    HW_COMPAT_2_7                                   \
+    {                                               \
+        .driver   = TYPE_SPAPR_PCI_HOST_BRIDGE,     \
+        .property = "mem_win_size",                 \
+        .value    = stringify(SPAPR_PCI_2_7_MMIO_WIN_SIZE),\
+    },                                              \
+    {                                               \
+        .driver   = TYPE_SPAPR_PCI_HOST_BRIDGE,     \
+        .property = "mem64_win_size",               \
+        .value    = "0",                            \
+    },
+
+static void phb_placement_2_7(sPAPRMachineState *spapr, uint32_t index,
+                              uint64_t *buid, hwaddr *pio,
+                              hwaddr *mmio32, hwaddr *mmio64,
+                              unsigned n_dma, uint32_t *liobns, Error **errp)
+{
+    /* Legacy PHB placement for pseries-2.7 and earlier machine types */
+    const uint64_t base_buid = 0x800000020000000ULL;
+    const hwaddr phb_spacing = 0x1000000000ULL; /* 64 GiB */
+    const hwaddr mmio_offset = 0xa0000000; /* 2 GiB + 512 MiB */
+    const hwaddr pio_offset = 0x80000000; /* 2 GiB */
+    const uint32_t max_index = 255;
+    const hwaddr phb0_alignment = 0x10000000000ULL; /* 1 TiB */
+
+    uint64_t ram_top = MACHINE(spapr)->ram_size;
+    hwaddr phb0_base, phb_base;
+    int i;
+
+    /* Do we have hotpluggable memory? */
+    if (MACHINE(spapr)->maxram_size > ram_top) {
+        /* Can't just use maxram_size, because there may be an
+         * alignment gap between normal and hotpluggable memory
+         * regions */
+        ram_top = spapr->hotplug_memory.base +
+            memory_region_size(&spapr->hotplug_memory.mr);
+    }
+
+    phb0_base = QEMU_ALIGN_UP(ram_top, phb0_alignment);
+
+    if (index > max_index) {
+        error_setg(errp, "\"index\" for PAPR PHB is too large (max %u)",
+                   max_index);
+        return;
+    }
+
+    *buid = base_buid + index;
+    for (i = 0; i < n_dma; ++i) {
+        liobns[i] = SPAPR_PCI_LIOBN(index, i);
+    }
+
+    phb_base = phb0_base + index * phb_spacing;
+    *pio = phb_base + pio_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_2_7_instance_options(MachineState *machine)
 {
@@ -2534,6 +2595,7 @@ static void spapr_machine_2_7_class_options(MachineClass *mc)
     spapr_machine_2_8_class_options(mc);
     smc->tcg_default_cpu = "POWER7";
     SET_MACHINE_COMPAT(mc, SPAPR_COMPAT_2_7);
+    smc->phb_placement = phb_placement_2_7;
 }
 
 DEFINE_SPAPR_MACHINE(2_7, "2.7", false);