[SeaBIOS] [PATCH V4 2/2] hw/pci: check if pci2pci bridges implement optional limit registers

[Michael S. Tsirkin]

On Thu, Apr 10, 2014 at 09:07:00PM +0300, Michael S. Tsirkin wrote:
> On Thu, Apr 10, 2014 at 08:44:18PM +0300, Marcel Apfelbaum wrote:
> > <I/O Base Register, I/O Limit Register> pair and
> > <Prefetchable Memory Base Register, Prefetchable Memory Limit Register> pair
> > are both optional.
> > Do not reserve ranges if the above registers are not implemented.
> > 
> > Signed-off-by: Marcel Apfelbaum <marcel.a at redhat.com>
> > ---
> >  src/fw/pciinit.c |  9 ++-------
> >  src/hw/pci.c     | 34 ++++++++++++++++++++++++++++++++++
> >  src/hw/pci.h     |  9 +++++++++
> >  3 files changed, 45 insertions(+), 7 deletions(-)
> > 
> > diff --git a/src/fw/pciinit.c b/src/fw/pciinit.c
> > index 9b5d7ad..bbaecd6 100644
> > --- a/src/fw/pciinit.c
> > +++ b/src/fw/pciinit.c
> > @@ -26,13 +26,6 @@
> >  #define PCI_BRIDGE_MEM_MIN    (1<<21)  // 2M == hugepage size
> >  #define PCI_BRIDGE_IO_MIN      0x1000  // mandated by pci bridge spec
> >  
> > -enum pci_region_type {
> > -    PCI_REGION_TYPE_IO,
> > -    PCI_REGION_TYPE_MEM,
> > -    PCI_REGION_TYPE_PREFMEM,
> > -    PCI_REGION_TYPE_COUNT,
> > -};
> > -
> >  static const char *region_type_name[] = {
> >      [ PCI_REGION_TYPE_IO ]      = "io",
> >      [ PCI_REGION_TYPE_MEM ]     = "mem",
> > @@ -681,6 +674,8 @@ static int pci_bios_check_devices(struct pci_bus *busses)
> >          for (type = 0; type < PCI_REGION_TYPE_COUNT; type++) {
> >              u64 align = (type == PCI_REGION_TYPE_IO) ?
> >                  PCI_BRIDGE_IO_MIN : PCI_BRIDGE_MEM_MIN;
> > +            if (!pci_bridge_has_region(s->bus_dev, type))
> > +                continue;
> >              if (pci_region_align(&s->r[type]) > align)
> >                   align = pci_region_align(&s->r[type]);
> >              u64 sum = pci_region_sum(&s->r[type]);
> > diff --git a/src/hw/pci.c b/src/hw/pci.c
> > index 77cdba2..d5979af 100644
> > --- a/src/hw/pci.c
> > +++ b/src/hw/pci.c
> > @@ -244,6 +244,40 @@ u8 pci_find_capability(struct pci_device *pci, u8 cap_id)
> >      return 0;
> >  }
> >  
> > +static int pci_config_is_reserved(struct pci_device *pci, u32 addr)
> 
> Why u32? It's u8 isn't it?
> 
> > +{
> > +    u8 val;
> > +
> > +    val = pci_config_readb(pci->bdf, addr);
> > +    pci_config_writeb(pci->bdf, addr, 0xFF);
> > +
> > +    if (!(pci_config_readb(pci->bdf, addr)))
> 
> () not needed after !
> 
> > +        return 1;
> > +
> > +    pci_config_writeb(pci->bdf, addr, val);
> > +    return 0;
> > +}
> 
> Above read simply saves the register value, write now restores it.
> It really should have a comment explaning what each stage does.
> 
> But I don't see why we still waste cycles on this save/restore
> dance. This is simply the result of making the API too generic.
> Open-code it below, and add a comment:
> 
> 
> /* Test whether bridge support forwarding of transactions
>  * of a specific type.
>  * Note: disables bridge's window registers as a side effect.
>  */
> int pci_bridge_has_region(struct pci_device *pci,
>                           enum pci_region_type region_type)
> {
>     u8 base;
> 
>     switch (region_type) {
>     case PCI_REGION_TYPE_IO:
>         base = PCI_IO_BASE;
>         break;
>     case PCI_REGION_TYPE_PREFMEM:
>         base = PCI_PREF_MEMORY_BASE;
>         break;
>     default:
>         /* Regular memory support is mandatory */
>         return 1;
>     }
> 
>     pci_config_writeb(pci->bdf, addr, 0xFF);
> 
>     return pci_config_readb(pci->bdf, addr) != 0;
> }
> 
> > +
> >  void
> >  pci_reboot(void)
> >  {
> > diff --git a/src/hw/pci.h b/src/hw/pci.h
> > index e828225..0aaa84c 100644
> > --- a/src/hw/pci.h
> > +++ b/src/hw/pci.h
> > @@ -12,6 +12,13 @@
> >  #define PCI_NUM_REGIONS 7
> >  #define PCI_BRIDGE_NUM_REGIONS 2
> >  
> > +enum pci_region_type {
> > +    PCI_REGION_TYPE_IO,
> > +    PCI_REGION_TYPE_MEM,
> > +    PCI_REGION_TYPE_PREFMEM,
> > +    PCI_REGION_TYPE_COUNT,
> > +};
> > +
> >  static inline u8 pci_bdf_to_bus(u16 bdf) {
> >      return bdf >> 8;
> >  }
> > @@ -117,6 +124,8 @@ int pci_init_device(const struct pci_device_id *ids
> >  struct pci_device *pci_find_init_device(const struct pci_device_id *ids
> >                                          , void *arg);
> >  u8 pci_find_capability(struct pci_device *pci, u8 cap_id);
> > +int pci_bridge_has_region(struct pci_device *pci,
> > +                          enum pci_region_type region_type);
> >  void pci_reboot(void);
> >  
> >  #endif
> > -- 
> > 1.8.3.1
> > 


And of course these are all nitpicks, would be better to fix
but the patch is otherwise correct.