Re: [Qemu-devel] vga optmization

["Glauber Costa" <glommer@gmail.com>]

On Mon, Nov 3, 2008 at 4:03 PM, Blue Swirl <blauwirbel@gmail.com> wrote:
> On 11/3/08, Glauber Costa <glommer@redhat.com> wrote:
>> Hi guys,
>>
>>  this is a port of current kvm vga memory optimization to our new
>>  infrastructure proposed by anthony. It's goal is to use as few
>>  kvm specific hooks as possible. In fact, the only one I'm relying
>>  on is enabling/disabling of logging. The rest, is pretty much general.
>>
>>  We map the linear frame buffer area as RAM, and then use dirty tracking
>>  to decide whether or not to update it. To be consistent with qemu,
>>  this version, differently from upstream kvm, tracks memory based on its
>>  physical address, represented by vram_offset, instead of vram_ptr, or
>>  any other construct.
>>
>>  Let me know what you think
>
> The patch does not apply, because of the kvm files. What patches do I
> need to apply first? I'd like to see how does the optimization apply
> to TCX.

Yes, you are missing kvm patches some time ago, which he plans to merge.

> This also may mean that some of my comments below can be invalid.
>
>>  +void set_vram_mapping(target_phys_addr_t begin, target_phys_addr_t end, ram_addr_t target)
>
> No "static"?
thanks, will update.

>
>>  +{
>>  +    /* align begin and end address */
>>  +    begin = begin & TARGET_PAGE_MASK;
>>  +    end = begin + VGA_RAM_SIZE;
>>  +    end = (end + TARGET_PAGE_SIZE -1 ) & TARGET_PAGE_MASK;
>
> This will fail if "end" is at the last page of the memory.

How so? I don't think it's possible for the addr 0xsomething0001 to be
valid, but 0x(something+1)000 to be not.

>
>>  +    uint32_t vga_io_memory;                                             \
>
> cpu_register_io_memory() returns an "int".

can it possibly be negative?
that said, of course I can change it for consistency, but I'd like to
understand it more

thanks


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

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