[PATCH RFC 2/6] i386/pc: Round up the hotpluggable memory within valid IOVA ranges

[Joao Martins <joao.m.martins@oracle.com>]

When accounting for allowed IOVA above 4G hole we also need to
consider the hotplug memory sits within allowed ranges.

Failure to do such validation, means that when we hotplug memory
and DMA map it, the DMA_MAP ioctl() fails given invalid IOVA use
but also leading to a catastrophic failure and exiting Qemu.

Similar to the region above 4G we need to make also do create a
region for the [ram .. maxram] GPA range, and select one which
is within the allowed IOVA ranges, preventing any such failures
in the future.

Co-developed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
 hw/i386/pc.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 49 insertions(+), 6 deletions(-)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 52a5473ba846..94497f22b908 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -909,7 +909,35 @@ static void init_usable_iova_ranges(void)
     }
 }
 
-static void add_memory_region(MemoryRegion *system_memory, MemoryRegion *ram,
+static hwaddr allowed_round_up(hwaddr base, hwaddr size)
+{
+    hwaddr base_aligned = ROUND_UP(base, 1 * GiB), addr;
+    uint32_t index;
+
+    for (index = 0; index < nb_iova_ranges; index++) {
+        hwaddr min_iova, max_iova;
+
+        min_iova = usable_iova_ranges[index].start;
+        max_iova = usable_iova_ranges[index].end;
+
+        if (max_iova < base_aligned) {
+            continue;
+        }
+
+        addr = MAX(ROUND_UP(min_iova, 1 * GiB), base_aligned);
+        if (addr > max_iova) {
+            continue;
+        }
+
+        if (max_iova - addr >= size) {
+            return addr;
+        }
+    }
+
+    return 0;
+}
+
+static hwaddr add_memory_region(MemoryRegion *system_memory, MemoryRegion *ram,
                                 hwaddr base, hwaddr size, hwaddr offset)
 {
     hwaddr start, region_size, resv_start, resv_end;
@@ -926,7 +954,7 @@ static void add_memory_region(MemoryRegion *system_memory, MemoryRegion *ram,
 
         assert(size >= region_size);
         if (size == region_size) {
-            return;
+            return start + region_size;
         }
 
         /*
@@ -935,7 +963,7 @@ static void add_memory_region(MemoryRegion *system_memory, MemoryRegion *ram,
          * would also be pointless.
          */
         if (index + 1 == nb_iova_ranges) {
-            return;
+            break;
         }
 
         resv_start = start + region_size;
@@ -946,6 +974,8 @@ static void add_memory_region(MemoryRegion *system_memory, MemoryRegion *ram,
 
         offset += region_size;
     }
+
+    return 0;
 }
 
 void pc_memory_init(PCMachineState *pcms,
@@ -961,6 +991,7 @@ void pc_memory_init(PCMachineState *pcms,
     MachineClass *mc = MACHINE_GET_CLASS(machine);
     PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(pcms);
     X86MachineState *x86ms = X86_MACHINE(pcms);
+    hwaddr maxram_start = 4 * GiB + x86ms->above_4g_mem_size;
 
     assert(machine->ram_size == x86ms->below_4g_mem_size +
                                 x86ms->above_4g_mem_size);
@@ -981,8 +1012,13 @@ void pc_memory_init(PCMachineState *pcms,
 
     e820_add_entry(0, x86ms->below_4g_mem_size, E820_RAM);
     if (x86ms->above_4g_mem_size > 0) {
-        add_memory_region(system_memory, machine->ram, 4 * GiB,
+        maxram_start = add_memory_region(system_memory, machine->ram, 4 * GiB,
                           x86ms->above_4g_mem_size, x86ms->below_4g_mem_size);
+        if (!maxram_start) {
+            error_report("unsupported amount of memory: %"PRIu64,
+                         x86ms->above_4g_mem_size);
+            exit(EXIT_FAILURE);
+        }
     }
 
     if (!pcmc->has_reserved_memory &&
@@ -1001,6 +1037,7 @@ void pc_memory_init(PCMachineState *pcms,
     if (pcmc->has_reserved_memory &&
         (machine->ram_size < machine->maxram_size)) {
         ram_addr_t device_mem_size = machine->maxram_size - machine->ram_size;
+        hwaddr device_mem_base;
 
         if (machine->ram_slots > ACPI_MAX_RAM_SLOTS) {
             error_report("unsupported amount of memory slots: %"PRIu64,
@@ -1015,8 +1052,14 @@ void pc_memory_init(PCMachineState *pcms,
             exit(EXIT_FAILURE);
         }
 
-        machine->device_memory->base =
-            ROUND_UP(0x100000000ULL + x86ms->above_4g_mem_size, 1 * GiB);
+        device_mem_base = allowed_round_up(maxram_start, device_mem_size);
+        if (!device_mem_base) {
+            error_report("unable to find device memory base for %"PRIu64
+                         " - %"PRIu64, maxram_start, device_mem_size);
+            exit(EXIT_FAILURE);
+        }
+
+        machine->device_memory->base = device_mem_base;
 
         if (pcmc->enforce_aligned_dimm) {
             /* size device region assuming 1G page max alignment per slot */
-- 
2.17.1