Re: [Qemu-devel] [PATCH 08/10] qxl: add vgamem_size_mb and vgamem_size

[Alon Levy]

On Tue, Jun 12, 2012 at 01:55:23PM +0200, Gerd Hoffmann wrote:
> On 06/12/12 11:37, Daniel P. Berrange wrote:
> > On Tue, Jun 12, 2012 at 09:51:12AM +0200, Gerd Hoffmann wrote:
> >> From: Alon Levy <address@hidden>
> >>
> >> In preperation for supporting a larger framebuffer for multiple monitors
> >> on a single card, add a property to qxl vgamem_size_mb, and corresponding
> >> byte sized vgamem_size, and use instead of VGA_RAM_SIZE.
> > 
> > How is this new property different from the existing 'vram_size' property
> > we can set for QXL ?
> > 
> >>          DEFINE_PROP_UINT32("ram_size_mb",  PCIQXLDevice, ram_size_mb, -1),
> >>          DEFINE_PROP_UINT32("vram_size_mb", PCIQXLDevice, vram32_size_mb, 
> >> -1),
> >>          DEFINE_PROP_UINT32("vram64_size_mb", PCIQXLDevice, vram_size_mb, 
> >> -1),
> >> +        DEFINE_PROP_UINT32("vgamem_mb", PCIQXLDevice, vgamem_size_mb, 8),
> >>          DEFINE_PROP_END_OF_LIST(),
> > 
> > Or indeed, can you describe the semantics of each of the different
> > ram size parameters here ?
> 
> Documenting this being a good idea just came across my mind these days
> too.  Ok here we go (should probably cut+paste to docs/qxl.txt):

Great idea!

> 
> The qxl device has two large memory regions:
> 
> Region #1 is called "ram" and is mapped to PCI bar 0.  This is again
> splitted into three parts:  The framebuffer at the start, the command
> rings at the end, and storage area for spice rendering commands and
> image data inbetween.
> 
> Region #2 is called "vram".  This is storage for images, called
> "surfaces" in spice.  Surfaces can be both source and target for spice
> rendering operations.  X11 can store offscreen pixmaps there for
> example.  Once qxl gets 3D support surfaces can also be used for textures.
> 
> Now for the properties:
> 
> vgamem_mb
>   specifies the size of the framebuffer portion of the "ram" region, in
>   megabytes.  Must be big enougth to hold the maximum display
s/enougth/enough/

>   resolution you want to use.  Replaces the fixed VGA_RAM_SIZE define.
>   Default is 8 or 16 MB depending on machine type with all patches of
>   this series applied (see last patch).
> 
> ram_size_mb
>   specifies the total size of the "ram" region, in megabytes.  Defaults
>   to 64 MB.  Must be larger than vgamem_mb obviously.
> 
> vram_size_mb
>   specifies the total size of the "vram" region, in megabytes.
>   Defaults to 64 MB.
> 
> vram64_size_mb
>   if this one is present and larger than vram_size_mb qxl will get an
>   additional 64bit pci bar.  Both 32bit and 64bit vram pci bars are
>   backed by the "vram" memory region, the 32bit bar is an alias mapping
>   for the first part of the 64bit pci bar.  This can be used to give
>   guests *lots* of vram without exhausting 32bit pci address space.
>   Obviously only useful for 64bit guests.  Requires cutting edge
>   seabios to get the 64bit bar actually mapped above 4G.
> 
> ram_size
>   specifies the total size of the "ram" region, in bytes.  For
>   compatibility with older qemu versions, ignored if ram_size_mb
>   property is present.
> 
> vram_size
>   specifies the total size of the "vram" region, in bytes.  For
>   compatibility with older qemu versions, ignored if vram_size_mb
>   property is present.
> 
> cheers,
>   Gerd
>