Hi, On 06/22/2018 12:43 PM, Logan Gunthorpe wrote: > When specifying PCI devices on the kernel command line using a > BDF, the bus numbers can change when adding or replacing a device, > changing motherboard firmware, or applying kernel parameters like > pci=assign-buses. When this happens, it is usually undesirable to > apply whatever command line tweak to the wrong device. > > Therefore, it is useful to be able to specify devices with a base > bus number and the path of devfns needed to get to it. (Similar to > the "device scope" structure in the Intel VT-d spec, Section 8.3.1.) > > Thus, we add an option to specify devices in the following format: > > [<domain>:]<bus>:<slot>.<func>[/<slot>.<func>]* Please explain the trailing '*'. I looked thru the code and it doesn't seem to look for it or care. > > The path can be any segment within the PCI hierarchy of any length and > determined through the use of 'lspci -t'. When specified this way, it is > less likely that a renumbered bus will result in a valid device specification > and the tweak won't be applied to the wrong device. > > Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx> > Reviewed-by: Stephen Bates <sbates@xxxxxxxxxxxx> > Acked-by: Christian König <christian.koenig@xxxxxxx> > Reviewed-by: Alex Williamson <alex.williamson@xxxxxxxxxx> > --- > Documentation/admin-guide/kernel-parameters.txt | 8 +- > drivers/pci/pci.c | 117 ++++++++++++++++++++---- > 2 files changed, 103 insertions(+), 22 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index e783bcefadac..a69947d9e14e 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -3000,7 +3000,7 @@ > or a set of devices (<pci_dev>). These are > specified in one of the following formats: > > - [<domain>:]<bus>:<slot>.<func> > + [<domain>:]<bus>:<slot>.<func>[/<slot>.<func>]* > pci:<vendor>:<device>[:<subvendor>:<subdevice>] > > Note: the first format specifies a PCI > @@ -3009,7 +3009,11 @@ > firmware changes, or due to changes caused > by other kernel parameters. If the > domain is left unspecified, it is > - taken to be zero. The second format > + taken to be zero. Optionally, a path > + to a device through multiple slot/function > + addresses can be specified after the base > + address (this is more robust against > + renumbering issues). The second format > selects devices using IDs from the > configuration space which may match multiple > devices in the system. thanks, -- ~Randy
