* [question]: Query regarding the PCI addresses @ 2021-07-14 6:33 Wenchao Hao 2021-07-14 16:54 ` Bjorn Helgaas 0 siblings, 1 reply; 7+ messages in thread From: Wenchao Hao @ 2021-07-14 6:33 UTC (permalink / raw) To: Bjorn Helgaas, linux-pci; +Cc: Wu Bo, Zhiqiang Liu, linfeilong, lijinlin3 Since linux identify PCI peripheral by [domain:bus:device:function] number like following, # lspci -D 0000:00:00.0 Host bridge: Red Hat, Inc. QEMU PCIe Host bridge 0000:00:01.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 92) 0000:00:02.0 PCI bridge: Intel Corporation 7500/5520/5500/X58 I/O Hub PCI Express Root Port 0 (rev 02) 0000:00:02.1 PCI bridge: Intel Corporation 7500/5520/5500/X58 I/O Hub PCI Express Root Port 0 (rev 02) 0000:00:02.2 PCI bridge: Intel Corporation 7500/5520/5500/X58 I/O Hub PCI Express Root Port 0 (rev 02) 0000:00:02.3 PCI bridge: Intel Corporation 7500/5520/5500/X58 I/O Hub PCI Express Root Port 0 (rev 02) 0000:01:00.0 PCI bridge: Red Hat, Inc. QEMU PCI-PCI bridge 0000:02:01.0 USB controller: Intel Corporation 82801DB/DBM (ICH4/ICH4-M) USB2 EHCI Controller (rev 10) 0000:02:02.0 Unclassified device [00ff]: Virtio: Virtio memory balloon 0000:02:03.0 SCSI storage controller: Virtio: Virtio SCSI 0000:02:04.0 Display controller: Virtio: Virtio GPU (rev 01) 0000:03:00.0 Ethernet controller: Virtio: Virtio network device (rev 01) Here are my questions: Are these [domain:bus:device:function] number come from hardware's physical connection or allocated by software dynamic? If hardware do not change, can we guarantee these number do not change after system reboot? If they are not fixed, then is there anyway I can get a fixed ID which can indicate physical connection. Thanks, Hope to get your help. ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [question]: Query regarding the PCI addresses 2021-07-14 6:33 [question]: Query regarding the PCI addresses Wenchao Hao @ 2021-07-14 16:54 ` Bjorn Helgaas 2021-07-14 17:26 ` Keith Busch 2021-07-16 13:59 ` Wenchao Hao 0 siblings, 2 replies; 7+ messages in thread From: Bjorn Helgaas @ 2021-07-14 16:54 UTC (permalink / raw) To: Wenchao Hao Cc: Bjorn Helgaas, linux-pci, Wu Bo, Zhiqiang Liu, linfeilong, lijinlin3, Matthew Wilcox [+cc Matthew for "lspci -P"] On Wed, Jul 14, 2021 at 02:33:37PM +0800, Wenchao Hao wrote: > Since linux identify PCI peripheral by [domain:bus:device:function] number > like following, > > # lspci -D > 0000:00:00.0 Host bridge: Red Hat, Inc. QEMU PCIe Host bridge > 0000:00:01.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 92) > 0000:00:02.0 PCI bridge: Intel Corporation 7500/5520/5500/X58 I/O Hub PCI > Express Root Port 0 (rev 02) > 0000:00:02.1 PCI bridge: Intel Corporation 7500/5520/5500/X58 I/O Hub PCI > Express Root Port 0 (rev 02) > 0000:00:02.2 PCI bridge: Intel Corporation 7500/5520/5500/X58 I/O Hub PCI > Express Root Port 0 (rev 02) > 0000:00:02.3 PCI bridge: Intel Corporation 7500/5520/5500/X58 I/O Hub PCI > Express Root Port 0 (rev 02) > 0000:01:00.0 PCI bridge: Red Hat, Inc. QEMU PCI-PCI bridge > 0000:02:01.0 USB controller: Intel Corporation 82801DB/DBM (ICH4/ICH4-M) > USB2 EHCI Controller (rev 10) > 0000:02:02.0 Unclassified device [00ff]: Virtio: Virtio memory balloon > 0000:02:03.0 SCSI storage controller: Virtio: Virtio SCSI > 0000:02:04.0 Display controller: Virtio: Virtio GPU (rev 01) > 0000:03:00.0 Ethernet controller: Virtio: Virtio network device (rev 01) > > Here are my questions: Are these [domain:bus:device:function] number > come from hardware's physical connection or allocated by software > dynamic? The device and function numbers are completely determined by the hardware and are not programmable. Bus numbers are programmable and are determined by the Secondary Bus Number of the bridge leading to the device. These bus numbers are generally programmed by the BIOS on x86. It's possible for Linux to reprogram them, but it generally leaves them alone if they are valid. On x86 with ACPI, the domain number comes from the _SEG method of the PNP0A03 device that describes the host bridge. This may correspond to a programmable hardware register, but that isn't visible to the OS and Linux has no way to change it. > If hardware do not change, can we guarantee these number do not > change after system reboot? For the typical x86 system with ACPI, this is really a question for the BIOS. If the hardware doesn't change, I would *expect* the domain/bus/device/function numbers to stay the same, but only BIOS folks can answer this definitively. > If they are not fixed, then is there anyway I can get a fixed ID > which can indicate physical connection. You can look at the "lspci -P" option. I'm not really familiar with this, but I think Matthew (cc'd) implemented it. Bjorn ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [question]: Query regarding the PCI addresses 2021-07-14 16:54 ` Bjorn Helgaas @ 2021-07-14 17:26 ` Keith Busch 2021-07-16 14:04 ` Wenchao Hao 2021-07-16 13:59 ` Wenchao Hao 1 sibling, 1 reply; 7+ messages in thread From: Keith Busch @ 2021-07-14 17:26 UTC (permalink / raw) To: Bjorn Helgaas Cc: Wenchao Hao, Bjorn Helgaas, linux-pci, Wu Bo, Zhiqiang Liu, linfeilong, lijinlin3, Matthew Wilcox On Wed, Jul 14, 2021 at 11:54:27AM -0500, Bjorn Helgaas wrote: > On Wed, Jul 14, 2021 at 02:33:37PM +0800, Wenchao Hao wrote: > > > If they are not fixed, then is there anyway I can get a fixed ID > > which can indicate physical connection. > > You can look at the "lspci -P" option. I'm not really familiar with > this, but I think Matthew (cc'd) implemented it. That option shows the parent devices for each listed device, but that may not produce the same output if BDf doesn't always enumerate the same. I think Wenchao was seeking some invariant device identification that can be used to look up its BDf. There's no PCI level requirement for uniquely identifying a specific device across changing topologies, so I don't think this is generically possible. ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [question]: Query regarding the PCI addresses 2021-07-14 17:26 ` Keith Busch @ 2021-07-16 14:04 ` Wenchao Hao 2021-07-16 14:25 ` Bjorn Helgaas 0 siblings, 1 reply; 7+ messages in thread From: Wenchao Hao @ 2021-07-16 14:04 UTC (permalink / raw) To: Keith Busch, Bjorn Helgaas Cc: Bjorn Helgaas, linux-pci, Wu Bo, Zhiqiang Liu, linfeilong, lijinlin3, Matthew Wilcox On 2021/7/15 1:26, Keith Busch wrote: > On Wed, Jul 14, 2021 at 11:54:27AM -0500, Bjorn Helgaas wrote: >> On Wed, Jul 14, 2021 at 02:33:37PM +0800, Wenchao Hao wrote: >> >>> If they are not fixed, then is there anyway I can get a fixed ID >>> which can indicate physical connection. >> You can look at the "lspci -P" option. I'm not really familiar with >> this, but I think Matthew (cc'd) implemented it. > That option shows the parent devices for each listed device, but that > may not produce the same output if BDf doesn't always enumerate the > same. > > I think Wenchao was seeking some invariant device identification that > can be used to look up its BDf. There's no PCI level requirement for > uniquely identifying a specific device across changing topologies, so I > don't think this is generically possible. > . Yes, I want a way to access device which can keep unchanged, a direction is according to hardware. If we have anyway which makes it possible for software can describe hardware connection would satisfy our demand. Wenchao ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [question]: Query regarding the PCI addresses 2021-07-16 14:04 ` Wenchao Hao @ 2021-07-16 14:25 ` Bjorn Helgaas 2021-07-20 2:05 ` Wenchao Hao 0 siblings, 1 reply; 7+ messages in thread From: Bjorn Helgaas @ 2021-07-16 14:25 UTC (permalink / raw) To: Wenchao Hao Cc: Keith Busch, Bjorn Helgaas, linux-pci, Wu Bo, Zhiqiang Liu, linfeilong, lijinlin3, Matthew Wilcox On Fri, Jul 16, 2021 at 10:04:51PM +0800, Wenchao Hao wrote: > On 2021/7/15 1:26, Keith Busch wrote: > > On Wed, Jul 14, 2021 at 11:54:27AM -0500, Bjorn Helgaas wrote: > > > On Wed, Jul 14, 2021 at 02:33:37PM +0800, Wenchao Hao wrote: > > > > > > > If they are not fixed, then is there anyway I can get a fixed ID > > > > which can indicate physical connection. > > > You can look at the "lspci -P" option. I'm not really familiar with > > > this, but I think Matthew (cc'd) implemented it. > > That option shows the parent devices for each listed device, but that > > may not produce the same output if BDf doesn't always enumerate the > > same. > > > > I think Wenchao was seeking some invariant device identification that > > can be used to look up its BDf. There's no PCI level requirement for > > uniquely identifying a specific device across changing topologies, so I > > don't think this is generically possible. > > Yes, I want a way to access device which can keep unchanged, a > direction is according to hardware. If we have anyway which makes > it possible for software can describe hardware connection would > satisfy our demand. I don't know whether this would be useful, but PCI does define an optional "Device Serial Number" extended capability. It has issues like the fact that many devices don't support it at all, and even on devices that do support it, the serial number may not actually be unique. There is minimal support for this in Linux (pci_get_dsn()), but it is currently not exposed to userspace via sysfs. Bjorn ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [question]: Query regarding the PCI addresses 2021-07-16 14:25 ` Bjorn Helgaas @ 2021-07-20 2:05 ` Wenchao Hao 0 siblings, 0 replies; 7+ messages in thread From: Wenchao Hao @ 2021-07-20 2:05 UTC (permalink / raw) To: Bjorn Helgaas Cc: Keith Busch, Bjorn Helgaas, linux-pci, Wu Bo, Zhiqiang Liu, linfeilong, lijinlin3, Matthew Wilcox On 2021/7/16 22:25, Bjorn Helgaas wrote: > On Fri, Jul 16, 2021 at 10:04:51PM +0800, Wenchao Hao wrote: >> On 2021/7/15 1:26, Keith Busch wrote: >>> On Wed, Jul 14, 2021 at 11:54:27AM -0500, Bjorn Helgaas wrote: >>>> On Wed, Jul 14, 2021 at 02:33:37PM +0800, Wenchao Hao wrote: >>>> >>>>> If they are not fixed, then is there anyway I can get a fixed ID >>>>> which can indicate physical connection. >>>> You can look at the "lspci -P" option. I'm not really familiar with >>>> this, but I think Matthew (cc'd) implemented it. >>> That option shows the parent devices for each listed device, but that >>> may not produce the same output if BDf doesn't always enumerate the >>> same. >>> >>> I think Wenchao was seeking some invariant device identification that >>> can be used to look up its BDf. There's no PCI level requirement for >>> uniquely identifying a specific device across changing topologies, so I >>> don't think this is generically possible. >> Yes, I want a way to access device which can keep unchanged, a >> direction is according to hardware. If we have anyway which makes >> it possible for software can describe hardware connection would >> satisfy our demand. > I don't know whether this would be useful, but PCI does define an > optional "Device Serial Number" extended capability. It has issues > like the fact that many devices don't support it at all, and even on > devices that do support it, the serial number may not actually be > unique. There is minimal support for this in Linux (pci_get_dsn()), > but it is currently not exposed to userspace via sysfs. > > Bjorn > . This "Device Serial Number" seems can not satisfy our demand because it is looks not a general ID. According to BIOS conclusion, if we can the hardware keeps unchanged, the BUS number would not change. We would put some restrictions as workaround temporarily. Thanks a lot for your suggestions. ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [question]: Query regarding the PCI addresses 2021-07-14 16:54 ` Bjorn Helgaas 2021-07-14 17:26 ` Keith Busch @ 2021-07-16 13:59 ` Wenchao Hao 1 sibling, 0 replies; 7+ messages in thread From: Wenchao Hao @ 2021-07-16 13:59 UTC (permalink / raw) To: Bjorn Helgaas Cc: Bjorn Helgaas, linux-pci, Wu Bo, Zhiqiang Liu, linfeilong, lijinlin3, Matthew Wilcox On 2021/7/15 0:54, Bjorn Helgaas wrote: > [+cc Matthew for "lspci -P"] > > On Wed, Jul 14, 2021 at 02:33:37PM +0800, Wenchao Hao wrote: >> Since linux identify PCI peripheral by [domain:bus:device:function] number >> like following, >> >> # lspci -D >> 0000:00:00.0 Host bridge: Red Hat, Inc. QEMU PCIe Host bridge >> 0000:00:01.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 92) >> 0000:00:02.0 PCI bridge: Intel Corporation 7500/5520/5500/X58 I/O Hub PCI >> Express Root Port 0 (rev 02) >> 0000:00:02.1 PCI bridge: Intel Corporation 7500/5520/5500/X58 I/O Hub PCI >> Express Root Port 0 (rev 02) >> 0000:00:02.2 PCI bridge: Intel Corporation 7500/5520/5500/X58 I/O Hub PCI >> Express Root Port 0 (rev 02) >> 0000:00:02.3 PCI bridge: Intel Corporation 7500/5520/5500/X58 I/O Hub PCI >> Express Root Port 0 (rev 02) >> 0000:01:00.0 PCI bridge: Red Hat, Inc. QEMU PCI-PCI bridge >> 0000:02:01.0 USB controller: Intel Corporation 82801DB/DBM (ICH4/ICH4-M) >> USB2 EHCI Controller (rev 10) >> 0000:02:02.0 Unclassified device [00ff]: Virtio: Virtio memory balloon >> 0000:02:03.0 SCSI storage controller: Virtio: Virtio SCSI >> 0000:02:04.0 Display controller: Virtio: Virtio GPU (rev 01) >> 0000:03:00.0 Ethernet controller: Virtio: Virtio network device (rev 01) >> >> Here are my questions: Are these [domain:bus:device:function] number >> come from hardware's physical connection or allocated by software >> dynamic? > The device and function numbers are completely determined by the > hardware and are not programmable. > > Bus numbers are programmable and are determined by the Secondary Bus > Number of the bridge leading to the device. These bus numbers are > generally programmed by the BIOS on x86. It's possible for Linux to > reprogram them, but it generally leaves them alone if they are valid. > > On x86 with ACPI, the domain number comes from the _SEG method of the > PNP0A03 device that describes the host bridge. This may correspond to > a programmable hardware register, but that isn't visible to the OS and > Linux has no way to change it. > >> If hardware do not change, can we guarantee these number do not >> change after system reboot? > For the typical x86 system with ACPI, this is really a question for > the BIOS. If the hardware doesn't change, I would *expect* the > domain/bus/device/function numbers to stay the same, but only BIOS > folks can answer this definitively. > >> If they are not fixed, then is there anyway I can get a fixed ID >> which can indicate physical connection. > You can look at the "lspci -P" option. I'm not really familiar with > this, but I think Matthew (cc'd) implemented it. > > Bjorn > . Thanks Bjorn for your great analysis and I would ask BIOS for their suggestions. I think we can put some constraints such as make BIOS give a stable bus number on our users to meet their needs of finding a stable path, although this method looks ugly. Wenchao ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2021-07-20 2:13 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-07-14 6:33 [question]: Query regarding the PCI addresses Wenchao Hao 2021-07-14 16:54 ` Bjorn Helgaas 2021-07-14 17:26 ` Keith Busch 2021-07-16 14:04 ` Wenchao Hao 2021-07-16 14:25 ` Bjorn Helgaas 2021-07-20 2:05 ` Wenchao Hao 2021-07-16 13:59 ` Wenchao Hao
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