> On Thu, Dec 31, 2020 at 07:08:23PM -0800, Bin Gao wrote:
> > On real hardware especially server platforms, there might be multiple
> > root buses, thus pci bus number could run up to 255. This patch fixed
> > pci_probe_devices() by allowing to scan all 256 pci bus numbers(0-255).
> >
> > Signed-off-by: Bin Gao <[email protected]>
> > ---
> > src/hw/pcidevice.c | 8 ++++++++
> > 1 file changed, 8 insertions(+)
> >
> > diff --git a/src/hw/pcidevice.c b/src/hw/pcidevice.c
> > index 8853cf7..8d9c401 100644
> > --- a/src/hw/pcidevice.c
> > +++ b/src/hw/pcidevice.c
> > @@ -26,6 +26,14 @@ pci_probe_devices(void)
> > struct hlist_node **pprev = &PCIDevices.first;
> > int extraroots = romfile_loadint("etc/extra-pci-roots", 0);
> > int bus = -1, lastbus = 0, rootbuses = 0, count=0;
> > +
> > + // There might be multiple PCI root buses on physical hardware
> > especially
> > + // server platforms, thus bus number could run up to the top value,
> > + // i.e. 0xff. Setting extraroots to 0xff to ensure we can enumerate all
> > + // PCI bus numbers.
> > + if (CONFIG_CSM)
> > + extraroots = 0xff;
>
> This doesn't look correct to me. It would take a noticeable amount of
> time to scan every possible PCI root bus. It would introduce a
> regression for any current users of CONFIG_CSM.
On real hardware scanning every possible PCI root bus wouldn't be slow so it's
not a problem. Would it be reasonable to scan all pci buses only on physical
hardware?
if (CONFIG_CSM && ! CONFIG_QEMU_HARDWARE)
extraroots = 0xff;
>
> The "etc/extra-pci-roots" config is intended to allow users to make
> these choices at runtime. If more configurability is desired on
> CONFIG_CSM, then it will be needed to figure out a way to pass options
> to SeaBIOS when in that mode.
So far I only need this extraroots config on CONFIG_CSM.
I didn't see an easy way to pass options from UEFI BIOS to SeaBIOS, unless we
extend the CSM protocol defined by Intel.
>
> -Kevin
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