[Qemu-devel] [PATCH 11/11] pc: count in 1Gb hugepage alignment when sizing hotplug-memory container

[Igor Mammedov]

if DIMMs with mized size/alignment are interleaved
in creation order it could lead hotplug-memory
container fragmentation and following inability
to use all RAM upto maxmem.
For example:
    -m 4G,slots=3,maxmem=7G
    -object memory-backend-file,id=mem-1,size=256M,mem-path=/pagesize-2MB
    -device pc-dimm,id=mem1,memdev=mem-1
    -object memory-backend-file,id=mem-2,size=1G,mem-path=/pagesize-1GB
    -device pc-dimm,id=mem2,memdev=mem-2
    -object memory-backend-file,id=mem-3,size=256M,mem-path=/pagesize-2MB
    -device pc-dimm,id=mem3,memdev=mem-3

creates fragment hotplug-memory container and doesn't
allow to use 1GB hugepage backend to cosume remainig 1Gb.

To ease managment factor in max 1Gb alignment for each
memory slot when sizing hotplug-memory region so that
regadless of fragmentaion it would be possible to add
max aligned DIMM.

Signed-off-by: Igor Mammedov <address@hidden>
---
 hw/i386/pc.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 0d9681e..9d2f800 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1288,6 +1288,11 @@ FWCfgState *pc_memory_init(MachineState *machine,
         pcms->hotplug_memory_base =
             ROUND_UP(0x100000000ULL + above_4g_mem_size, 1ULL << 30);
 
+        if (pcms->enforce_aligned_dimm) {
+            /* size hotplug region assuming 1G page max alignment per slot */
+            hotplug_mem_size += (1ULL << 30) * machine->ram_slots;
+        }
+
         if ((pcms->hotplug_memory_base + hotplug_mem_size) <
             hotplug_mem_size) {
             error_report("unsupported amount of maximum memory: " RAM_ADDR_FMT,
-- 
1.8.3.1