Re: [PATCH] fix -kernel option

[Anthony Liguori <anthony-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org>]

Izik Eidus wrote:
> Anthony Liguori wrote:
>> Glauber de Oliveira Costa wrote:
>>  
>>> Currently, the -kernel option is not working.
>>>
>>> Reason is, because we're registering chunks for regions 0-0xa0000 and
>>> 0x100000-ram_size, the phys_ram_addr + PA is broken.
>>>       
>>
>> I think this patch is a reasonable work-around but the long term 
>> solution is probably going to have to be making sure that nothing 
>> makes the phys_ram_addr + PA assumption.  With > 4GB of memory, this 
>> assumption is broken because of the BIOS/PCI holes anyway. 
> we can always allocate 300 mbs of junk :)

Well, it may not be so bad.  We can certainly malloc() those 300mbs.  
They'll never be touched by anyone so it doesn't actually increase the 
resident size.

> but i agree with you, and i guess it is important to the dirty bit 
> tracking that no one will touch this
> memory without the formal functions anyway (at least for qemu)

Yes, the only concern I have is that I really want to be able maintain 
that physically contiguous memory is virtually contiguous in QEMU.  This 
is an important assumption in virtio.  It's less important if 
phys_ram_base + PA works or not as long as that property is preserved.

Regards,

Anthony Liguori

>>  I guess we could preserve this assumption though by burning some 
>> memory.
>>
>> Thoughts?
>>
>> Regards,
>>
>> Anthony Liguori
>>
>>  
>>> The real fix should be to rewrite all the load_linux() code to not rely
>>> on this, but meanwhile, filling in the gap up to 0xc0000 - the 
>>> beginning
>>> of extended memory - makes it work again
>>>
>>> Signed-off-by: Glauber de Oliveira Costa <gcosta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
>>> ---
>>>  qemu/hw/pc.c |   11 ++++++++---
>>>  1 files changed, 8 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/qemu/hw/pc.c b/qemu/hw/pc.c
>>> index 6c71b09..e4a5f2d 100644
>>> --- a/qemu/hw/pc.c
>>> +++ b/qemu/hw/pc.c
>>> @@ -725,13 +725,18 @@ static void pc_init1(ram_addr_t ram_size, int 
>>> vga_ram_size, int boot_device,
>>>  #ifdef USE_KVM
>>>   #ifdef KVM_CAP_USER_MEMORY
>>>      if (kvm_allowed && 
>>> kvm_qemu_check_extension(KVM_CAP_USER_MEMORY)) {
>>> +        ram_addr = qemu_ram_alloc(0xa0000);
>>> +        cpu_register_physical_memory(0, 0xa0000, ram_addr);
>>> +        kvm_cpu_register_physical_memory(0, 0xa0000, ram_addr);
>>> +
>>> +    /* move the pointer up to 0xc0000, which is the next
>>> +           address we'll touch */
>>> +        qemu_ram_alloc(0x20000);
>>> +
>>>          ram_addr = qemu_ram_alloc(ram_size - 0x100000);
>>>          cpu_register_physical_memory(0x100000, ram_size - 0x100000, 
>>> ram_addr);
>>>          kvm_cpu_register_physical_memory(0x100000, ram_size - 
>>> 0x100000,
>>>                                           ram_addr);
>>> -        ram_addr = qemu_ram_alloc(0xa0000);
>>> -        cpu_register_physical_memory(0, 0xa0000, ram_addr);
>>> -        kvm_cpu_register_physical_memory(0, 0xa0000, ram_addr);
>>>      } else
>>>   #endif
>>>  #endif
>>>       
>>
>>
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>
>


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