VGA address mapping?

VGA address mapping?

[Saksena, Abhishek]

Hi
I am implementing a VGA Device model. The model provides functions to read/write VGA memory space.

Just for testing I want to capture memory reads/writes to addresses 0xA0000->0xC0000 and forward it to my VGA model.


I have used following function to create physical ram

int kvm_create  (       kvm_context_t<file:///C:/Documents%20and%20Settings/asaksena/Desktop/march_onwards/kvmsocket/doc/htmlkvm/structkvm__context.html>       kvm,
                unsigned long   phys_mem_bytes,
                void **         phys_mem
        )

The function comments says that this creates a new virtual machine, maps physical RAM to it, and creates a virtual CPU for it. Memory gets mapped for addresses 0->0xA0000, 0xC0000->phys_mem_bytes.



I was expecting mimio read/write callbacks to capture transactions between 0xA0000->0xC0000  but I don't see that happening.



My question is how I can configure KVM to forward me reads/writes for VGA address space?





Thanks

Abhishek

RE: VGA address mapping?

[Saksena, Abhishek]

Would also like to mention I am not using Qemu and building some basic IO models around KVM (only using libkvm.h)

-Abhishek
________________________________
From: Saksena, Abhishek
Sent: Tuesday, July 21, 2009 11:13 AM
To: kvm@vger.kernel.org
Subject: VGA address mapping?

Hi
I am implementing a VGA Device model. The model provides functions to read/write VGA memory space.

Just for testing I want to capture memory reads/writes to addresses 0xA0000->0xC0000 and forward it to my VGA model.


I have used following function to create physical ram

int kvm_create  (       kvm_context_t<file:///C:/Documents%20and%20Settings/asaksena/Desktop/march_onwards/kvmsocket/doc/htmlkvm/structkvm__context.html>       kvm,
                unsigned long   phys_mem_bytes,
                void **         phys_mem
        )

The function comments says that this creates a new virtual machine, maps physical RAM to it, and creates a virtual CPU for it. Memory gets mapped for addresses 0->0xA0000, 0xC0000->phys_mem_bytes.



I was expecting mimio read/write callbacks to capture transactions between 0xA0000->0xC0000  but I don't see that happening.



My question is how I can configure KVM to forward me reads/writes for VGA address space?





Thanks

Abhishek

Re: VGA address mapping?

[Gleb Natapov]

On Tue, Jul 21, 2009 at 04:06:10PM -0700, Saksena, Abhishek wrote:
> Would also like to mention I am not using Qemu and building some basic IO models around KVM (only using libkvm.h)
> 
> -Abhishek
> ________________________________
> From: Saksena, Abhishek
> Sent: Tuesday, July 21, 2009 11:13 AM
> To: kvm@vger.kernel.org
> Subject: VGA address mapping?
> 
> Hi
> I am implementing a VGA Device model. The model provides functions to read/write VGA memory space.
> 
> Just for testing I want to capture memory reads/writes to addresses 0xA0000->0xC0000 and forward it to my VGA model.
> 
> 
> I have used following function to create physical ram
> 
> int kvm_create  (       kvm_context_t<file:///C:/Documents%20and%20Settings/asaksena/Desktop/march_onwards/kvmsocket/doc/htmlkvm/structkvm__context.html>       kvm,
>                 unsigned long   phys_mem_bytes,
>                 void **         phys_mem
>         )
> 
> The function comments says that this creates a new virtual machine, maps physical RAM to it, and creates a virtual CPU for it. Memory gets mapped for addresses 0->0xA0000, 0xC0000->phys_mem_bytes.
> 
This indeed what comment says, but looking at the code I don't see it
using phys_mem_bytes/phys_mem parameters at all.

Look at QEMU code how memory is created.
> 
> 
> I was expecting mimio read/write callbacks to capture transactions between 0xA0000->0xC0000  but I don't see that happening.
> 
> 
> 
> My question is how I can configure KVM to forward me reads/writes for VGA address space?
> 
> 
> 
> 
> 
> Thanks
> 
> Abhishek
> --
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--
			Gleb.

Re: VGA address mapping?

[Alexander Graf]

On 22.07.2009, at 09:48, Gleb Natapov wrote:

> On Tue, Jul 21, 2009 at 04:06:10PM -0700, Saksena, Abhishek wrote:
>> Would also like to mention I am not using Qemu and building some  
>> basic IO models around KVM (only using libkvm.h)
>>
>> -Abhishek
>> ________________________________
>> From: Saksena, Abhishek
>> Sent: Tuesday, July 21, 2009 11:13 AM
>> To: kvm@vger.kernel.org
>> Subject: VGA address mapping?
>>
>> Hi
>> I am implementing a VGA Device model. The model provides functions  
>> to read/write VGA memory space.
>>
>> Just for testing I want to capture memory reads/writes to addresses  
>> 0xA0000->0xC0000 and forward it to my VGA model.
>>
>>
>> I have used following function to create physical ram
>>
>> int kvm_create  (       kvm_context_t<file:///C:/Documents%20and%20Settings/asaksena/Desktop/march_onwards/kvmsocket/doc/htmlkvm/structkvm__context.html 
>> >       kvm,
>>                unsigned long   phys_mem_bytes,
>>                void **         phys_mem
>>        )
>>
>> The function comments says that this creates a new virtual machine,  
>> maps physical RAM to it, and creates a virtual CPU for it. Memory  
>> gets mapped for addresses 0->0xA0000, 0xC0000->phys_mem_bytes.
>>
> This indeed what comment says, but looking at the code I don't see it
> using phys_mem_bytes/phys_mem parameters at all.

I'm not sure about libkvm, but the real KVM logic is "memory is not  
mapped -> MMIO". So if you just don't map it, you should get MMIO  
exits on that range.

Keep in mind that there are people out there trying to get rid of  
libkvm :-)

Alex