On Mon, Dec 07, 2015 at 02:05:14PM +0200, Marcel Apfelbaum wrote: > PCIe downstream ports (Root Ports and switches Downstream Ports) appear > to firmware as PCI-PCI bridges and a 4K IO space is allocated for them > even if there is no device behind them requesting IO space, > all that for hotplug purpose. > > However, PCIe devices can work without IO, so there is no need > to allocate IO space for hotplug. > > Signed-off-by: Marcel Apfelbaum <[email protected]>
Acked-by: Michael S. Tsirkin <[email protected]> > --- > v1 -> v2: > - Addressed Gerd's comments: > - move pci_find_capability out of the loop and call it only once. > - more descriptive names for variables > > Notes: > - This patch fixes a 15 PCIe Root ports limitation when used with > virtio pci-express devices having no IO space requirements: > <qemu cmd line> -M q35 `for i in {1..15}; do echo -device > ioh3420,chassis=$i,id=b$i -device virtio-net-pci,bus=b$i,disable-legacy=on; > done` > - There is a patch on QEMU devel list that tackles the problem from another > angle > by allowing PCIe downstream ports to not forward IO requests. > https://lists.gnu.org/archive/html/qemu-devel/2015-11/msg04478.html > - The mentioned patch is of course not enough and also requires management > software intervention. > > Thanks, > Marcel > > src/fw/pciinit.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/src/fw/pciinit.c b/src/fw/pciinit.c > index 7b8aab7..c31c2fa 100644 > --- a/src/fw/pciinit.c > +++ b/src/fw/pciinit.c > @@ -645,9 +645,8 @@ pci_region_create_entry(struct pci_bus *bus, struct > pci_device *dev, > return entry; > } > > -static int pci_bus_hotplug_support(struct pci_bus *bus) > +static int pci_bus_hotplug_support(struct pci_bus *bus, u8 pcie_cap) > { > - u8 pcie_cap = pci_find_capability(bus->bus_dev, PCI_CAP_ID_EXP, 0); > u8 shpc_cap; > > if (pcie_cap) { > @@ -727,7 +726,8 @@ static int pci_bios_check_devices(struct pci_bus *busses) > */ > parent = &busses[0]; > int type; > - int hotplug_support = pci_bus_hotplug_support(s); > + u8 pcie_cap = pci_find_capability(s->bus_dev, PCI_CAP_ID_EXP, 0); > + int hotplug_support = pci_bus_hotplug_support(s, pcie_cap); > for (type = 0; type < PCI_REGION_TYPE_COUNT; type++) { > u64 align = (type == PCI_REGION_TYPE_IO) ? > PCI_BRIDGE_IO_MIN : PCI_BRIDGE_MEM_MIN; > @@ -736,7 +736,8 @@ static int pci_bios_check_devices(struct pci_bus *busses) > if (pci_region_align(&s->r[type]) > align) > align = pci_region_align(&s->r[type]); > u64 sum = pci_region_sum(&s->r[type]); > - if (!sum && hotplug_support) > + int resource_optional = pcie_cap && (type == PCI_REGION_TYPE_IO); > + if (!sum && hotplug_support && !resource_optional) > sum = align; /* reserve min size for hot-plug */ > u64 size = ALIGN(sum, align); > int is64 = pci_bios_bridge_region_is64(&s->r[type], > -- > 2.1.0 _______________________________________________ SeaBIOS mailing list [email protected] http://www.seabios.org/mailman/listinfo/seabios
