[Qemu-devel] [PATCH] split memory allocation

[Qemu-devel] [PATCH] split memory allocation

[Glauber Costa]

Right now, kvm keeps the memory allocation split, so we can
handle different areas in different ways. This schema works with qemu
too, so it appears to be the common ground.

This patch proposes using this common ground for everyone, by spliting
raw qemu.

Signed-off-by: Glauber Costa <glommer@redhat.com>
---
 hw/pc.c |   16 ++++++++++++----
 1 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/hw/pc.c b/hw/pc.c
index 435c7d4..d6084ee 100644
--- a/hw/pc.c
+++ b/hw/pc.c
@@ -777,16 +777,24 @@ static void pc_init1(ram_addr_t ram_size, int vga_ram_size,
     vmport_init();
 
     /* allocate RAM */
-    ram_addr = qemu_ram_alloc(ram_size);
-    cpu_register_physical_memory(0, below_4g_mem_size, ram_addr);
+    ram_addr = qemu_ram_alloc(0xa0000);
+    cpu_register_physical_memory(0, 0xa0000, ram_addr);
+
+    ram_addr = qemu_ram_alloc(0x100000 - 0xa0000);   /* hole */
+    ram_addr = qemu_ram_alloc(below_4g_mem_size - 0x100000);
+    cpu_register_physical_memory(0x100000,
+                 below_4g_mem_size - 0x100000,
+                 ram_addr);
 
     /* above 4giga memory allocation */
     if (above_4g_mem_size > 0) {
-        cpu_register_physical_memory((target_phys_addr_t) 0x100000000ULL,
+        ram_addr = qemu_ram_alloc(above_4g_mem_size);
+        cpu_register_physical_memory(0x100000000ULL,
                                      above_4g_mem_size,
-                                     ram_addr + below_4g_mem_size);
+                                     ram_addr);
     }
 
+
     /* allocate VGA RAM */
     vga_ram_addr = qemu_ram_alloc(vga_ram_size);
 
-- 
1.5.5.1

Re: [Qemu-devel] [PATCH] split memory allocation

[Aurelien Jarno]

Glauber Costa a écrit :
> Right now, kvm keeps the memory allocation split, so we can
> handle different areas in different ways. This schema works with qemu
> too, so it appears to be the common ground.
> 
> This patch proposes using this common ground for everyone, by spliting
> raw qemu.
> 
> Signed-off-by: Glauber Costa <glommer@redhat.com>
> ---
>  hw/pc.c |   16 ++++++++++++----
>  1 files changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/pc.c b/hw/pc.c
> index 435c7d4..d6084ee 100644
> --- a/hw/pc.c
> +++ b/hw/pc.c
> @@ -777,16 +777,24 @@ static void pc_init1(ram_addr_t ram_size, int vga_ram_size,
>      vmport_init();
>  
>      /* allocate RAM */
> -    ram_addr = qemu_ram_alloc(ram_size);
> -    cpu_register_physical_memory(0, below_4g_mem_size, ram_addr);
> +    ram_addr = qemu_ram_alloc(0xa0000);
> +    cpu_register_physical_memory(0, 0xa0000, ram_addr);
> +
> +    ram_addr = qemu_ram_alloc(0x100000 - 0xa0000);   /* hole */

What the point of allocating RAM for the memory hole if it is not mapped?

> +    ram_addr = qemu_ram_alloc(below_4g_mem_size - 0x100000);
> +    cpu_register_physical_memory(0x100000,
> +                 below_4g_mem_size - 0x100000,
> +                 ram_addr);
>  
>      /* above 4giga memory allocation */
>      if (above_4g_mem_size > 0) {
> -        cpu_register_physical_memory((target_phys_addr_t) 0x100000000ULL,
> +        ram_addr = qemu_ram_alloc(above_4g_mem_size);
> +        cpu_register_physical_memory(0x100000000ULL,
>                                       above_4g_mem_size,
> -                                     ram_addr + below_4g_mem_size);
> +                                     ram_addr);
>      }
>  
> +
>      /* allocate VGA RAM */
>      vga_ram_addr = qemu_ram_alloc(vga_ram_size);
>  


-- 
  .''`.  Aurelien Jarno	            | GPG: 1024D/F1BCDB73
 : :' :  Debian developer           | Electrical Engineer
 `. `'   aurel32@debian.org         | aurelien@aurel32.net
   `-    people.debian.org/~aurel32 | www.aurel32.net

Re: [Qemu-devel] [PATCH] split memory allocation

[Anthony Liguori]

Aurelien Jarno wrote:
> Glauber Costa a écrit :
>   
>> Right now, kvm keeps the memory allocation split, so we can
>> handle different areas in different ways. This schema works with qemu
>> too, so it appears to be the common ground.
>>
>> This patch proposes using this common ground for everyone, by spliting
>> raw qemu.
>>
>> Signed-off-by: Glauber Costa <glommer@redhat.com>
>> ---
>>  hw/pc.c |   16 ++++++++++++----
>>  1 files changed, 12 insertions(+), 4 deletions(-)
>>
>> diff --git a/hw/pc.c b/hw/pc.c
>> index 435c7d4..d6084ee 100644
>> --- a/hw/pc.c
>> +++ b/hw/pc.c
>> @@ -777,16 +777,24 @@ static void pc_init1(ram_addr_t ram_size, int vga_ram_size,
>>      vmport_init();
>>  
>>      /* allocate RAM */
>> -    ram_addr = qemu_ram_alloc(ram_size);
>> -    cpu_register_physical_memory(0, below_4g_mem_size, ram_addr);
>> +    ram_addr = qemu_ram_alloc(0xa0000);
>> +    cpu_register_physical_memory(0, 0xa0000, ram_addr);
>> +
>> +    ram_addr = qemu_ram_alloc(0x100000 - 0xa0000);   /* hole */
>>     
>
> What the point of allocating RAM for the memory hole if it is not mapped?
>   

If you don't, you violate the phys_ram_base + PA assumption for all of 
memory.  No code should rely on this but practically speaking, there is 
still some code in QEMU that does.

Since the RAM is never touched, it doesn't actually impact the RSS size 
so it's not all that important.

Regards,

Anthony Liguori

Re: [Qemu-devel] [PATCH] split memory allocation

[Glauber Costa]

On Thu, Sep 11, 2008 at 09:35:44AM -0500, Anthony Liguori wrote:
> Aurelien Jarno wrote:
>> Glauber Costa a écrit :
>>   
>>> Right now, kvm keeps the memory allocation split, so we can
>>> handle different areas in different ways. This schema works with qemu
>>> too, so it appears to be the common ground.
>>>
>>> This patch proposes using this common ground for everyone, by spliting
>>> raw qemu.
>>>
>>> Signed-off-by: Glauber Costa <glommer@redhat.com>
>>> ---
>>>  hw/pc.c |   16 ++++++++++++----
>>>  1 files changed, 12 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/hw/pc.c b/hw/pc.c
>>> index 435c7d4..d6084ee 100644
>>> --- a/hw/pc.c
>>> +++ b/hw/pc.c
>>> @@ -777,16 +777,24 @@ static void pc_init1(ram_addr_t ram_size, int vga_ram_size,
>>>      vmport_init();
>>>       /* allocate RAM */
>>> -    ram_addr = qemu_ram_alloc(ram_size);
>>> -    cpu_register_physical_memory(0, below_4g_mem_size, ram_addr);
>>> +    ram_addr = qemu_ram_alloc(0xa0000);
>>> +    cpu_register_physical_memory(0, 0xa0000, ram_addr);
>>> +
>>> +    ram_addr = qemu_ram_alloc(0x100000 - 0xa0000);   /* hole */
>>>     
>>
>> What the point of allocating RAM for the memory hole if it is not mapped?
>>   
>
> If you don't, you violate the phys_ram_base + PA assumption for all of  
> memory.  No code should rely on this but practically speaking, there is  
> still some code in QEMU that does.
>
> Since the RAM is never touched, it doesn't actually impact the RSS size  
> so it's not all that important.
>
> Regards,
>
> Anthony Liguori
>
Precisely.

We actually saw this a while ago. the kernel loader was broken due to that.

Re: [Qemu-devel] [PATCH] split memory allocation

[Avi Kivity]

Glauber Costa wrote:
> Right now, kvm keeps the memory allocation split, so we can
> handle different areas in different ways. This schema works with qemu
> too, so it appears to be the common ground.
>
> This patch proposes using this common ground for everyone, by spliting
> raw qemu.
>   

I would rather see qemu switched to using memory slots.  The big chunk 
approach doesn't work well with memory hotplug (or with device hotplug 
when the device provides a memory resource).

-- 
error compiling committee.c: too many arguments to function

[Qemu-devel] [PATCH] split memory allocation

[Glauber Costa]

Right now, kvm keeps the memory allocation split, so we can
handle different areas in different ways. This schema works with qemu
too, so it appears to be the common ground.

This patch proposes using this common ground for everyone, by spliting
raw qemu.

Signed-off-by: Glauber Costa <glommer@redhat.com>
---
 hw/pc.c |   16 ++++++++++++----
 1 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/hw/pc.c b/hw/pc.c
index 435c7d4..d6084ee 100644
--- a/hw/pc.c
+++ b/hw/pc.c
@@ -777,16 +777,24 @@ static void pc_init1(ram_addr_t ram_size, int vga_ram_size,
     vmport_init();
 
     /* allocate RAM */
-    ram_addr = qemu_ram_alloc(ram_size);
-    cpu_register_physical_memory(0, below_4g_mem_size, ram_addr);
+    ram_addr = qemu_ram_alloc(0xa0000);
+    cpu_register_physical_memory(0, 0xa0000, ram_addr);
+
+    ram_addr = qemu_ram_alloc(0x100000 - 0xa0000);   /* hole */
+    ram_addr = qemu_ram_alloc(below_4g_mem_size - 0x100000);
+    cpu_register_physical_memory(0x100000,
+                 below_4g_mem_size - 0x100000,
+                 ram_addr);
 
     /* above 4giga memory allocation */
     if (above_4g_mem_size > 0) {
-        cpu_register_physical_memory((target_phys_addr_t) 0x100000000ULL,
+        ram_addr = qemu_ram_alloc(above_4g_mem_size);
+        cpu_register_physical_memory(0x100000000ULL,
                                      above_4g_mem_size,
-                                     ram_addr + below_4g_mem_size);
+                                     ram_addr);
     }
 
+
     /* allocate VGA RAM */
     vga_ram_addr = qemu_ram_alloc(vga_ram_size);
 
-- 
1.5.5.1

[Qemu-devel] [PATCH] split memory allocation

[Glauber Costa]

Right now, kvm keeps the memory allocation split, so we can
handle different areas in different ways. This schema works with qemu
too, so it appears to be the common ground.

This patch proposes using this common ground for everyone, by spliting
raw qemu.

Signed-off-by: Glauber Costa <glommer@redhat.com>
---
 hw/pc.c |   20 ++++++++++++++++----
 1 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/hw/pc.c b/hw/pc.c
index 435c7d4..9fd1bdf 100644
--- a/hw/pc.c
+++ b/hw/pc.c
@@ -777,16 +777,28 @@ static void pc_init1(ram_addr_t ram_size, int vga_ram_size,
     vmport_init();
 
     /* allocate RAM */
-    ram_addr = qemu_ram_alloc(ram_size);
-    cpu_register_physical_memory(0, below_4g_mem_size, ram_addr);
+    ram_addr = qemu_ram_alloc(0xa0000);
+    cpu_register_physical_memory(0, 0xa0000, ram_addr);
+
+    /* Allocate, even though we won't register, so we don't break the
+     * phys_ram_base + PA assumption. This range includes vga (0xa0000 - 0xc0000),
+     * and some bios areas, which will be registered later
+     */
+    ram_addr = qemu_ram_alloc(0x100000 - 0xa0000);
+    ram_addr = qemu_ram_alloc(below_4g_mem_size - 0x100000);
+    cpu_register_physical_memory(0x100000,
+                 below_4g_mem_size - 0x100000,
+                 ram_addr);
 
     /* above 4giga memory allocation */
     if (above_4g_mem_size > 0) {
-        cpu_register_physical_memory((target_phys_addr_t) 0x100000000ULL,
+        ram_addr = qemu_ram_alloc(above_4g_mem_size);
+        cpu_register_physical_memory(0x100000000ULL,
                                      above_4g_mem_size,
-                                     ram_addr + below_4g_mem_size);
+                                     ram_addr);
     }
 
+
     /* allocate VGA RAM */
     vga_ram_addr = qemu_ram_alloc(vga_ram_size);
 
-- 
1.5.5.1

Re: [Qemu-devel] [PATCH] split memory allocation

[Anthony Liguori]

Glauber Costa wrote:
> Right now, kvm keeps the memory allocation split, so we can
> handle different areas in different ways. This schema works with qemu
> too, so it appears to be the common ground.
>
> This patch proposes using this common ground for everyone, by spliting
> raw qemu.
>   

Applied.  Thanks.

Regards,

Anthony Liguori

Re: [Qemu-devel] [PATCH] split memory allocation

[Glauber Costa]

On Mon, Sep 15, 2008 at 1:00 PM, Anthony Liguori <anthony@codemonkey.ws> wrote:
> Glauber Costa wrote:
>>
>> Right now, kvm keeps the memory allocation split, so we can
>> handle different areas in different ways. This schema works with qemu
>> too, so it appears to be the common ground.
>>
>> This patch proposes using this common ground for everyone, by spliting
>> raw qemu.
>>
>
> Applied.  Thanks.
you're welcome ;-)

>
> Regards,
>
> Anthony Liguori
>
>
>
>



-- 
Glauber Costa.
"Free as in Freedom"
http://glommer.net

"The less confident you are, the more serious you have to act."