Re: [Qemu-devel] [PATCH v2 4/4] xen-all: Pass max_ram_below_4g to xen_hvm_init.

[Don Slutz <dslutz@verizon.com>]

On 03/17/14 13:55, Stefano Stabellini wrote:
> On Mon, 17 Mar 2014, Don Slutz wrote:
>> On 03/16/14 12:10, Stefano Stabellini wrote:
>>> On Tue, 11 Mar 2014, Don Slutz wrote:
>>>> This is the xen part of "pc & q35: Add new object pc-memory-layout."
>>>>
>>>> Signed-off-by: Don Slutz<dslutz@verizon.com>
>>>> ---
>>>>    hw/i386/pc_piix.c    |  4 ++--
>>>>    hw/i386/pc_q35.c     |  4 ++--
>>>>    include/hw/xen/xen.h |  4 ++--
>>>>    xen-all.c            | 41 ++++++++++++++++++++++-------------------
>>>>    xen-stub.c           |  4 ++--
>>>>    5 files changed, 30 insertions(+), 27 deletions(-)
>>>>
>>>> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
>>>> index 964ea33..691fc5d 100644
>>>> --- a/hw/i386/pc_piix.c
>>>> +++ b/hw/i386/pc_piix.c
>>>> @@ -131,8 +131,8 @@ static void pc_init1(QEMUMachineInitArgs *args,
>>>>            below_4g_mem_size = args->ram_size;
>>>>        }
>>>>    -    if (xen_enabled() && xen_hvm_init(&below_4g_mem_size,
>>>> &above_4g_mem_size,
>>>> -                                      &ram_memory) != 0) {
>>>> +    if (xen_enabled() && xen_hvm_init(max_ram_below_4g,
>>>> &below_4g_mem_size,
>>>> +                                      &above_4g_mem_size, &ram_memory) !=
>>>> 0) {
>>>>            fprintf(stderr, "xen hardware virtual machine initialisation
>>>> failed\n");
>>>>            exit(1);
>>>>        }
>>>> diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
>>>> index c95e6e2..8e1c417 100644
>>>> --- a/hw/i386/pc_q35.c
>>>> +++ b/hw/i386/pc_q35.c
>>>> @@ -120,8 +120,8 @@ static void pc_q35_init(QEMUMachineInitArgs *args)
>>>>            below_4g_mem_size = args->ram_size;
>>>>        }
>>>>    -    if (xen_enabled() && xen_hvm_init(&below_4g_mem_size,
>>>> &above_4g_mem_size,
>>>> -                                      &ram_memory) != 0) {
>>>> +    if (xen_enabled() && xen_hvm_init(max_ram_below_4g,
>>>> &below_4g_mem_size,
>>>> +                                      &above_4g_mem_size, &ram_memory) !=
>>>> 0) {
>>>>            fprintf(stderr, "xen hardware virtual machine initialisation
>>>> failed\n");
>>>>            exit(1);
>>>>        }
>>>> diff --git a/include/hw/xen/xen.h b/include/hw/xen/xen.h
>>>> index 0769db2..fda559a 100644
>>>> --- a/include/hw/xen/xen.h
>>>> +++ b/include/hw/xen/xen.h
>>>> @@ -41,8 +41,8 @@ int xen_init(QEMUMachine *machine);
>>>>    void xenstore_store_pv_console_info(int i, struct CharDriverState *chr);
>>>>      #if defined(NEED_CPU_H) && !defined(CONFIG_USER_ONLY)
>>>> -int xen_hvm_init(ram_addr_t *below_4g_mem_size, ram_addr_t
>>>> *above_4g_mem_size,
>>>> -                 MemoryRegion **ram_memory);
>>>> +int xen_hvm_init(ram_addr_t max_ram_below_4g, ram_addr_t
>>>> *below_4g_mem_size,
>>>> +                 ram_addr_t *above_4g_mem_size, MemoryRegion
>>>> **ram_memory);
>>>>    void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size,
>>>>                       struct MemoryRegion *mr);
>>>>    void xen_modified_memory(ram_addr_t start, ram_addr_t length);
>>>> diff --git a/xen-all.c b/xen-all.c
>>>> index c64300c..48ba335 100644
>>>> --- a/xen-all.c
>>>> +++ b/xen-all.c
>>>> @@ -155,32 +155,34 @@ qemu_irq *xen_interrupt_controller_init(void)
>>>>      /* Memory Ops */
>>>>    -static void xen_ram_init(ram_addr_t *below_4g_mem_size,
>>>> +static void xen_ram_init(ram_addr_t ram_size, ram_addr_t
>>>> max_ram_below_4g,
>>>> +                         ram_addr_t *below_4g_mem_size,
>>>>                             ram_addr_t *above_4g_mem_size,
>>>> -                         ram_addr_t ram_size, MemoryRegion
>>>> **ram_memory_p)
>>>> +                         MemoryRegion **ram_memory_p)
>>>>    {
>>>>        MemoryRegion *sysmem = get_system_memory();
>>>>        ram_addr_t block_len;
>>>>    -    block_len = ram_size;
>>>> -    if (ram_size >= HVM_BELOW_4G_RAM_END) {
>>>> -        /* Xen does not allocate the memory continuously, and keep a hole
>>>> at
>>>> -         * HVM_BELOW_4G_MMIO_START of HVM_BELOW_4G_MMIO_LENGTH
>>>> -         */
>>>> -        block_len += HVM_BELOW_4G_MMIO_LENGTH;
>>>> +    if (!max_ram_below_4g) {
>>>> +        if (ram_size >= HVM_BELOW_4G_RAM_END) {
>>>> +            *above_4g_mem_size = ram_size - HVM_BELOW_4G_RAM_END;
>>>> +            *below_4g_mem_size = HVM_BELOW_4G_RAM_END;
>>>> +        } else {
>>>> +            *above_4g_mem_size = 0;
>>>> +            *below_4g_mem_size = ram_size;
>>>> +        }
>>>> +    }
>>> Instead of treating max_ram_below_4g as a special case, couldn't
>>> initialize it to HVM_BELOW_4G_RAM_END?
>> Since max_ram_below_4g is used and initialize in normal QEMU code
>> where HVM_BELOW_4G_RAM_END is not defined, I do not see how to
>> do this outside of this routine without adding a new routine for this.
>   
> You can simply do this at the beginning of xen_ram_init:
>
> max_ram_below_4g = max_ram_below_4g ? max_ram_below_4g : HVM_BELOW_4G_RAM_END;
>
> my comment was about code readability, I didn't mean change any
> functionalities.

So the partial code delta:

      MemoryRegion *sysmem = get_system_memory();
      ram_addr_t block_len;

-    block_len = ram_size;
-    if (ram_size >= HVM_BELOW_4G_RAM_END) {
-        /* Xen does not allocate the memory continuously, and keep a hole at
-         * HVM_BELOW_4G_MMIO_START of HVM_BELOW_4G_MMIO_LENGTH
-         */
-        block_len += HVM_BELOW_4G_MMIO_LENGTH;
-    }
-    memory_region_init_ram(&ram_memory, NULL, "xen.ram", block_len);
-    *ram_memory_p = &ram_memory;
-    vmstate_register_ram_global(&ram_memory);
-
-    if (ram_size >= HVM_BELOW_4G_RAM_END) {
-        *above_4g_mem_size = ram_size - HVM_BELOW_4G_RAM_END;
-        *below_4g_mem_size = HVM_BELOW_4G_RAM_END;
+    max_ram_below_4g = max_ram_below_4g ? max_ram_below_4g : HVM_BELOW_4G_RAM_END;
+    if (ram_size >= max_ram_below_4g) {
+        *above_4g_mem_size = ram_size - max_ram_below_4g;
+        *below_4g_mem_size = max_ram_below_4g;
      } else {
          *above_4g_mem_size = 0;
          *below_4g_mem_size = ram_size;
      }
+    if (!*above_4g_mem_size) {
+        block_len = ram_size;
+    } else {
+        /* Xen does not allocate the memory continuously, and keep a hole of
+         * of the size computed above or passed in. */
+        block_len = (1ULL << 32) + *above_4g_mem_size;
+    }
+    memory_region_init_ram(&ram_memory, NULL, "xen.ram", block_len);
+    *ram_memory_p = &ram_memory;
+    vmstate_register_ram_global(&ram_memory);


Which does redo the calculation of above and below when max_ram_below_4g
is set, is better for code readability.

I am happy to send a v2 with this, just do not want to send too many versions.

    -Don Slutz