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SubjectRe: [PATCH 2/6] pci: Scan all functions when probing while running over Jailhouse
On 2018-02-22 21:57, Bjorn Helgaas wrote:
> On Mon, Jan 22, 2018 at 07:12:46AM +0100, Jan Kiszka wrote:
>> From: Jan Kiszka <>
>> PCI and PCIBIOS probing only scans devices at function number 0/8/16/...
>> Subdevices (e.g. multiqueue) have function numbers which are not a
>> multiple of 8.
> Suggested text:
> Per PCIe r4.0, sec, multi-function devices are required to
> have a function 0. Therefore, Linux scans for devices at function 0
> (devfn 0/8/16/...) and only scans for other functions if function 0
> has its Multi-Function Device bit set or ARI or SR-IOV indicate
> there are more functions.
> The Jailhouse hypervisor may pass individual functions of a
> multi-function device to a guest without passing function 0, which
> means a Linux guest won't find them.
> Change Linux PCI probing so it scans all function numbers when
> running as a guest over Jailhouse.
> This is technically prohibited by the spec, so it is possible that
> PCI devices without the Multi-Function Device bit set may have
> unexpected behavior in response to this probe.
>> The simple hypervisor Jailhouse passes subdevices directly w/o providing
>> a virtual PCI topology like KVM. As a consequence a PCI passthrough from
>> Jailhouse to a guest will not be detected by Linux.
>> Based on patch by Benedikt Spranger, adding Jailhouse probing to avoid
>> changing the behavior in the absence of the hypervisor.
>> CC: Benedikt Spranger <>
>> Signed-off-by: Jan Kiszka <>
> With subject change to:
> PCI: Scan all functions when running over Jailhouse
> Acked-by: Bjorn Helgaas <>

Thanks, all suggestions picked up for next round.


Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux

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