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Re: [Qemu-devel] [PATCH] split memory allocation
From: |
Glauber Costa |
Subject: |
Re: [Qemu-devel] [PATCH] split memory allocation |
Date: |
Thu, 11 Sep 2008 11:42:03 -0300 |
User-agent: |
Mutt/1.5.18 (2008-05-17) |
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 <address@hidden>
>>> ---
>>> 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.