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Two reasons: 1. Can be used by both x86 and ARM VMs 2. Add a vendor-specific pci capability to these ports, with recommended window sizes (io/mem/prefmem) for the firmware for more efficient resource allocation.
Posted upstream: https://lists.gnu.org/archive/html/qemu-devel/2016-11/msg04310.html
Hi Marcel According to comment1, "Generic PCIe root ports" is the same with "ioh3420", what is the different between bz1390316 and bz1390329 ? I am not very clear about it. Thanks Jing Zhao
(In reply to jingzhao from comment #2) > Hi Marcel > > According to comment1, "Generic PCIe root ports" is the same with > "ioh3420", what is the different between bz1390316 and bz1390329 ? I am not > very clear about it. > > Thanks > Jing Zhao Hi, Generic PCIe Root ports exports the same functionality as IOH3420 indeed, however bz1390329 refers to PCIe-PCI bridge that has other functionality, to allow legacy PCI devices (instead of the DMI-PCI bridge i82801b11) Thanks, Marcel
> Hi, > > Generic PCIe Root ports exports the same functionality as IOH3420 indeed, > however bz1390329 refers to PCIe-PCI bridge that has other functionality, to > allow legacy PCI devices (instead of the DMI-PCI bridge i82801b11) Marcel, thanks very much firstly, and also following questions confused me 1. "bz1390329 allow legacy PCI devices", you mean instead of i82801b11 bridge, how about the connection PRL for the legacy PCI device? connect to the Generic PCIe-PCI bridge(bz1390329) or connect to the pcie.0, in other words, what's the common connection? 2. As QE known, i82801b11 bridge will be not used on rhel7.4, that means we will use the PCIe-PCI bridge that bz1390329 provided in qemu? qemu will provide Generic PCIe-PCI bridge all the time, never use the i82801b11 bridge? 3. the usage of the two bridge, are the following right? 1) pcie.0 --- Generic PCIe Root Ports (/multifunction) -- pcie devices 2) pcie.0 --- Generic PCIe-PCI bridge --- PCI devices Thanks Jing Zhao
(In reply to jingzhao from comment #4) > > Hi, > > > > Generic PCIe Root ports exports the same functionality as IOH3420 indeed, > > however bz1390329 refers to PCIe-PCI bridge that has other functionality, to > > allow legacy PCI devices (instead of the DMI-PCI bridge i82801b11) > > Marcel, thanks very much firstly, and also following questions confused me > > 1. "bz1390329 allow legacy PCI devices", you mean instead of i82801b11 > bridge, how about the connection PRL for the legacy PCI device? connect to > the Generic PCIe-PCI bridge(bz1390329) or connect to the pcie.0, in other > words, what's the common connection? > Yes, PCI devices should be Integrated Endpoints (plugged into pcie.0) or connected to the new device - the PCIe-PCI bridge. We want to deprecate the i82801b11 bridge. > 2. As QE known, i82801b11 bridge will be not used on rhel7.4, that means we > will use the PCIe-PCI bridge that bz1390329 provided in qemu? yes, but the new bridge will not be ready for 7.4 . on 7.4 PCI devices will be plugged only into pcie.0 bus. qemu will > provide Generic PCIe-PCI bridge all the time, never use the i82801b11 bridge? > once the device will be ready, it will completely replace the i82801b11 > 3. the usage of the two bridge, are the following right? > > 1) pcie.0 --- Generic PCIe Root Ports (/multifunction) -- pcie devices > 2) pcie.0 --- Generic PCIe-PCI bridge --- PCI devices > Correct and also: 3) pcie.0 --- PCI devices Thanks, Marcel > > Thanks > Jing Zhao
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHSA-2017:2392