Re: [libvirt] [PATCH v2 1/4] conf: restrict what type of buses will accept a pci-bridge

A pci-bridge has *almost* the same rules as a legacy PCI endpoint device for where it can be automatically connected, and until now both had been considered identical. There is one pairing that is okay when specifically requested by the user (i.e. manual assignment), but we want to avoid it when auto-assigning addresses - plugging a pci-bridge

directly into pcie-root (it is cleaner to plug in a dmi-to-pci-bridge, then plug the pci-bridge into that).   In order to allow that difference, this patch makes a separate CONNECT_TYPE for pci-bridge, and uses it to restrict auto-assigned addresses for pci-bridges to be only on pci-root, pci-expander-bus, dmi-to-pci-bridge, or on another pci-bridge.   NB: As with other discouraged-but-seem-to-work configurations (e.g. plugging a legacy PCI device into a pcie-root-port) if someone *really* wants to, they can still force a pci-bridge to be plugged into pcie-root (by manually specifying its PCI address.) ---   src/conf/domain_addr.c | 29 ++++++++++++++++++++++-------   src/conf/domain_addr.h |  4 +++-   2 files changed, 25 insertions(+), 8 deletions(-)   diff --git a/src/conf/domain_addr.c b/src/conf/domain_addr.c index c533edb..88e44df 100644 --- a/src/conf/domain_addr.c +++ b/src/conf/domain_addr.c @@ -51,11 +51,14 @@ virDomainPCIControllerModelToConnectType(virDomainControllerModelPCI model)           return 0;          case VIR_DOMAIN_CONTROLLER_MODEL_PCI_BRIDGE: -        /* pci-bridge is treated like a standard -         * PCI endpoint device, because it can plug into any -         * standard PCI slot (it just can't be hotplugged). +        /* pci-bridge is treated like a standard PCI endpoint device +         * when its address is manually assigned, but needs special +         * treatment when auto-assigning addresses (in that case we +         * avoid plugging into anything except pci-root, +         * dmi-to-pci-bridge, pci-expander-bus, or another +         * pci-bridge).            */ -        return VIR_PCI_CONNECT_TYPE_PCI_DEVICE; +        return VIR_PCI_CONNECT_TYPE_PCI_BRIDGE;

      case VIR_DOMAIN_CONTROLLER_MODEL_PCI_EXPANDER_BUS:           return VIR_PCI_CONNECT_TYPE_PCI_EXPANDER_BUS; @@ -110,6 +113,12 @@ virDomainPCIAddressFlagsCompatible(virPCIDeviceAddressPtr addr,            */           if (devFlags & VIR_PCI_CONNECT_HOTPLUGGABLE)               busFlags |= VIR_PCI_CONNECT_HOTPLUGGABLE; +        /* if the device is a pci-bridge, allow manually +         * assigning to any bus that would also accept a +         * standard PCI device. +         */ +        if (devFlags & VIR_PCI_CONNECT_TYPE_PCI_BRIDGE) +            devFlags |= VIR_PCI_CONNECT_TYPE_PCI_DEVICE;