Re: [SeaBIOS] [PATCH 4/8] seabios: pciinit: make pci bar assigner preferchable memory aware.

[Kevin O'Connor]

On Thu, Jun 17, 2010 at 08:03:12PM +0900, Isaku Yamahata wrote:
> Make pci bar assigner preferchable memory aware.
> This is needed for PCI bridge support because memory space and
> prefetchable memory space is filtered independently based on
> memory base/limit and prefetchable memory base/limit of pci bridge.
> On bus 0, such a distinction isn't necessary so keep existing behavior
> by checking bus=0.
> [...]
>      pci_bios_io_addr = 0xc000;
>      pci_bios_mem_addr = BUILD_PCIMEM_START;
>
> +    /* pci_bios_mem_addr + <some value> */
> +    pci_bios_prefmem_addr = pci_bios_mem_addr + 0x08000000;

How can we be sure that the "mem" space doesn't overlap with the
"prefmem" space?

-Kevin

[PATCH 4/8] seabios: pciinit: make pci bar assigner preferchable memory aware.

[Isaku Yamahata]

On Mon, Jun 21, 2010 at 10:20:14PM -0400, Kevin O'Connor wrote:
> On Thu, Jun 17, 2010 at 08:03:12PM +0900, Isaku Yamahata wrote:
> > Make pci bar assigner preferchable memory aware.
> > This is needed for PCI bridge support because memory space and
> > prefetchable memory space is filtered independently based on
> > memory base/limit and prefetchable memory base/limit of pci bridge.
> > On bus 0, such a distinction isn't necessary so keep existing behavior
> > by checking bus=0.
> > [...]
> >      pci_bios_io_addr = 0xc000;
> >      pci_bios_mem_addr = BUILD_PCIMEM_START;
> >
> > +    /* pci_bios_mem_addr + <some value> */
> > +    pci_bios_prefmem_addr = pci_bios_mem_addr + 0x08000000;
>
> How can we be sure that the "mem" space doesn't overlap with the
> "prefmem" space?

No check at the moment. Which way do you prefer?

- do nothing and pray that user wouldn't add so many devices.
  (current implementation)
  I chose this implementation because the existing code doesn't
  check whether mem area overlaps with around 4GB area which is
  used for other purpose.

- add overlap check.
  If mem area reaches to perfmem area, abandon further mapping with warning.

- Add one more path to scan pci bus to sum up size of mem and prefmem
  and calculate pci_bios_prefmem_addr more smartly.
  If mapping area is lacking, warn it and map them as possible as much.

- any better idea?
> -Kevin
>
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[PATCH 4/8] seabios: pciinit: make pci bar assigner preferchable memory aware.

[Kevin O'Connor]

On Tue, Jun 22, 2010 at 12:22:50PM +0900, Isaku Yamahata wrote:
> On Mon, Jun 21, 2010 at 10:20:14PM -0400, Kevin O'Connor wrote:
> > How can we be sure that the "mem" space doesn't overlap with the
> > "prefmem" space?
>
> No check at the moment. Which way do you prefer?
>
> - do nothing and pray that user wouldn't add so many devices.
>   (current implementation)
>   I chose this implementation because the existing code doesn't
>   check whether mem area overlaps with around 4GB area which is
>   used for other purpose.
>
> - add overlap check.
>   If mem area reaches to perfmem area, abandon further mapping with warning.

I'd probably go with "add overlap check".  I could be convinced
otherwise though.

-Kevin