[Qemu-devel] [RFC PATCH v2] spapr: Enable use of huge pages

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 07/09/2014 05:46 PM, Paolo Bonzini wrote:> Il 09/07/2014 07:57, Alexey Kardashevskiy ha scritto:
>> 0b183fc87 "memory: move mem_path handling to
>> memory_region_allocate_system_memory" disabled -mempath use for all
>> machines that do not use memory_region_allocate_system_memory() to
>> register RAM. Since SPAPR uses memory_region_init_ram(), the huge pages
>> support was disabled for it.
>>
>> This replaces memory_region_init_ram()+vmstate_register_ram_global() with
>> memory_region_allocate_system_memory() to get huge pages back.
>>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Hu Tao <hutao@cn.fujitsu.com>
>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>> ---
>>  hw/ppc/spapr.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
>> index a23c0f0..8fa9f7e 100644
>> --- a/hw/ppc/spapr.c
>> +++ b/hw/ppc/spapr.c
>> @@ -1337,8 +1337,8 @@ static void ppc_spapr_init(MachineState *machine)
>>          ram_addr_t nonrma_base = rma_alloc_size;
>>          ram_addr_t nonrma_size = spapr->ram_limit - rma_alloc_size;
>>
>> -        memory_region_init_ram(ram, NULL, "ppc_spapr.ram", nonrma_size);
>> -        vmstate_register_ram_global(ram);
>> +        memory_region_allocate_system_memory(ram, NULL, "ppc_spapr.ram",
>> +                                             nonrma_size);
> 
> The reason why I didn't do this in the simple way is that depending on the
> value of nonrma_base you may get smaller hugepages than you wanted.
> 
> For example, if the hugepage size is 1G but nonrma_base is 32M, you will
> not be able to get a page size larger than 32M.
> 
> Depending on the value of nonrma_base, it may be better to allocate the
> whole spapr->ram_limit to ppc_spapr.ram, and just ignore the first part of it.
> 
> I see in target-ppc/kvm.c that rma_alloc_size is capped to 256M, and  in
> practice it is 128M (arch/powerpc/kvm/book3s_hv_builtin.c.  Considering
> that Linux overcommits so the memory isn't lost in the non-hugepage case, I
> think it's better to just waste the 128M of address space.
> 
> Paolo
> 
>>          memory_region_add_subregion(sysmem, nonrma_base, ram);
>>      }

Did you mean something like below? If so, I have to change MR tree and
place RMA under RAM, I guess.
I'll try to give it a try tomorrow on bare PPC970.




---
 hw/ppc/spapr.c       | 19 ++++++++++++-------
 target-ppc/kvm.c     |  9 +--------
 target-ppc/kvm_ppc.h |  2 +-
 3 files changed, 14 insertions(+), 16 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index a23c0f0..47ae6c1 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1223,6 +1223,7 @@ static void ppc_spapr_init(MachineState *machine)
     int i;
     MemoryRegion *sysmem = get_system_memory();
     MemoryRegion *ram = g_new(MemoryRegion, 1);
+    MemoryRegion *rma_region;
     hwaddr rma_alloc_size;
     hwaddr node0_size = (nb_numa_nodes > 1) ? numa_info[0].node_mem : ram_size;
     uint32_t initrd_base = 0;
@@ -1230,6 +1231,7 @@ static void ppc_spapr_init(MachineState *machine)
     long load_limit, rtas_limit, fw_size;
     bool kernel_le = false;
     char *filename;
+    void *rma = NULL;
 
     msi_supported = true;
 
@@ -1239,7 +1241,7 @@ static void ppc_spapr_init(MachineState *machine)
     cpu_ppc_hypercall = emulate_spapr_hypercall;
 
     /* Allocate RMA if necessary */
-    rma_alloc_size = kvmppc_alloc_rma("ppc_spapr.rma", sysmem);
+    rma_alloc_size = kvmppc_alloc_rma(&rma);
 
     if (rma_alloc_size == -1) {
         hw_error("qemu: Unable to create RMA\n");
@@ -1333,13 +1335,16 @@ static void ppc_spapr_init(MachineState *machine)
 
     /* allocate RAM */
     spapr->ram_limit = ram_size;
-    if (spapr->ram_limit > rma_alloc_size) {
-        ram_addr_t nonrma_base = rma_alloc_size;
-        ram_addr_t nonrma_size = spapr->ram_limit - rma_alloc_size;
+    memory_region_allocate_system_memory(ram, NULL, "ppc_spapr.ram",
+                                         spapr->ram_limit);
+    memory_region_add_subregion(sysmem, 0, ram);
 
-        memory_region_init_ram(ram, NULL, "ppc_spapr.ram", nonrma_size);
-        vmstate_register_ram_global(ram);
-        memory_region_add_subregion(sysmem, nonrma_base, ram);
+    if (rma_alloc_size && rma) {
+        rma_region = g_new(MemoryRegion, 1);
+        memory_region_init_ram_ptr(rma_region, NULL, "ppc_spapr.rma",
+                                   rma_alloc_size, rma);
+        vmstate_register_ram_global(rma_region);
+        memory_region_add_subregion(sysmem, 0, rma_region);
     }
 
     filename = qemu_find_file(QEMU_FILE_TYPE_BIOS, "spapr-rtas.bin");
diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
index 995706a..9ca14d2 100644
--- a/target-ppc/kvm.c
+++ b/target-ppc/kvm.c
@@ -1582,13 +1582,11 @@ int kvmppc_smt_threads(void)
 }
 
 #ifdef TARGET_PPC64
-off_t kvmppc_alloc_rma(const char *name, MemoryRegion *sysmem)
+off_t kvmppc_alloc_rma(void **rma)
 {
-    void *rma;
     off_t size;
     int fd;
     struct kvm_allocate_rma ret;
-    MemoryRegion *rma_region;
 
     /* If cap_ppc_rma == 0, contiguous RMA allocation is not supported
      * if cap_ppc_rma == 1, contiguous RMA allocation is supported, but
@@ -1617,11 +1615,6 @@ off_t kvmppc_alloc_rma(const char *name, MemoryRegion *sysmem)
         return -1;
     };
 
-    rma_region = g_new(MemoryRegion, 1);
-    memory_region_init_ram_ptr(rma_region, NULL, name, size, rma);
-    vmstate_register_ram_global(rma_region);
-    memory_region_add_subregion(sysmem, 0, rma_region);
-
     return size;
 }
 
diff --git a/target-ppc/kvm_ppc.h b/target-ppc/kvm_ppc.h
index 33c2171..bc5d2e8 100644
--- a/target-ppc/kvm_ppc.h
+++ b/target-ppc/kvm_ppc.h
@@ -31,7 +31,7 @@ int kvmppc_or_tsr_bits(PowerPCCPU *cpu, uint32_t tsr_bits);
 int kvmppc_set_tcr(PowerPCCPU *cpu);
 int kvmppc_booke_watchdog_enable(PowerPCCPU *cpu);
 #ifndef CONFIG_USER_ONLY
-off_t kvmppc_alloc_rma(const char *name, MemoryRegion *sysmem);
+off_t kvmppc_alloc_rma(void **rma);
 bool kvmppc_spapr_use_multitce(void);
 void *kvmppc_create_spapr_tce(uint32_t liobn, uint32_t window_size,
                               uint64_t bus_offset, uint32_t page_shift,
-- 
2.0.0