Re: [Qemu-devel] [PATCH v3 0/3] add check for PCIe root ports and downstream ports

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Sep 01, 2014 at 09:29:16PM +0800, arei.gonglei@huawei.com wrote:
> From: Gonglei <arei.gonglei@huawei.com>
> 
> Root ports and downstream ports of switches are the hot
> pluggable ports in a PCI Express hierarchy.
> PCI Express supports chip-to-chip interconnect, a PCIe link can
> only connect one pci device/Switch/EndPoint or PCI-bridge.
> 
> 7.3. Configuration Transaction Rules (PCI Express specification 3.0)
> 7.3.1. Device Number
> 
> Downstream Ports that do not have ARI Forwarding enabled must
> associate only Device 0 with the device attached to the Logical Bus
> representing the Link from the Port.
> 
> In QEMU, ARI Forwarding is enabled defualt at emulation of PCIe
> ports. ARI Forwarding enable setting at firmware/OS Control handoff.
> If the bit is Set when a non-ARI Device is present, the non-ARI
> Device can respond to Configuration Space accesses under what it
> interprets as being different Device Numbers, and its Functions can
> be aliased under multiple Device Numbers, generally leading to
> undesired behavior.
> 
> So, for pci devices attached in pcie root ports or downstream pots,
> we shoud assure that its slot is non-zero. For pcie devcies, which
> ARP capbility is not enabled, we also should assure that its slot
> is non-zero.

So what is this patchset about?
Is there a broken configuration that this helps prevent?
Can you show the command-line please?

In particular, non-express devices behind an express bus
shouldn't exist according to spec, but do in practice, and guests
seem to be able to handle them.

> Changes since v2:
>  - make patch 1/3 more simpler and safer.(Hu Tao)
>  - change check logic from pci.c to pcie.c and change function's name
>  - judge devcies' ARI capbility instead of PCIe ports' ARI Forwarding
>    (Michael)
>  - add trivial patch 3/3
>  - update patch's commit messages and code comments.
> 
> Thanks for your reviewing.
>  
> Changes since v1:
>  - using object_dynamic_cast() instead of simple string comparing (Paolo)
>  - add ARI Forwarding enable bit check
>  - using pcie_cap_get_type() instead of simple string comparing (Marcel)
>  - fix some other comments.
> 
> Gonglei (3):
>   qdev: Introduce a function to get qbus's parent
>   pcie: add check for ari capability of pcie devices
>   pcie: remove confused comments
> 
>  hw/core/qdev.c         |  9 ++++++++
>  hw/pci/pci.c           |  4 ++++
>  hw/pci/pcie.c          | 59 +++++++++++++++++++++++++++++++++++++++++++-------
>  include/hw/pci/pcie.h  |  1 +
>  include/hw/qdev-core.h |  1 +
>  5 files changed, 66 insertions(+), 8 deletions(-)
> 
> -- 
> 1.7.12.4
>