Re: Recent commits reject RPi4B booting: pcib0 vs. pcib1 "rman_manage_region: <pcib1 memory window> request" leads to panic

On Wed, Feb 14, 2024 at 9:08 AM John Baldwin <jhb@freebsd.org> wrote:

> On 2/12/24 5:57 PM, Mark Millard wrote:
> > On Feb 12, 2024, at 16:36, Mark Millard <marklmi@yahoo.com> wrote:
> >
> >> On Feb 12, 2024, at 16:10, Mark Millard <marklmi@yahoo.com> wrote:
> >>
> >>> On Feb 12, 2024, at 12:00, Mark Millard <marklmi@yahoo.com> wrote:
> >>>
> >>>> [Gack: I was looking at the wrong vintage of source code, predating
> >>>> your changes: wrong system used.]
> >>>>
> >>>>
> >>>> On Feb 12, 2024, at 10:41, Mark Millard <marklmi@yahoo.com> wrote:
> >>>>
> >>>>> On Feb 12, 2024, at 09:32, John Baldwin <jhb@freebsd.org> wrote:
> >>>>>
> >>>>>> On 2/9/24 8:13 PM, Mark Millard wrote:
> >>>>>>> Summary:
> >>>>>>> pcib0: <BCM2838-compatible PCI-express controller> mem
> 0x7d500000-0x7d50930f irq 80,81 on simplebus2
> >>>>>>> pcib0: parsing FDT for ECAM0:
> >>>>>>> pcib0:  PCI addr: 0xc0000000, CPU addr: 0x600000000, Size:
> 0x40000000
> >>>>>>> . . .
> >>>>>>> rman_manage_region: <pcib1 memory window> request: start
> 0x600000000, end 0x6000fffff
> >>>>>>> panic: Failed to add resource to rman
> >>>>>>
> >>>>>> Hmmm, I suspect this is due to the way that bus_translate_resource
> works which is
> >>>>>> fundamentally broken.  It rewrites the start address of a resource
> in-situ instead
> >>>>>> of keeping downstream resources separate from the upstream
> resources.   For example,
> >>>>>> I don't see how you could ever release a resource in this design
> without completely
> >>>>>> screwing up your rman.  That is, I expect trying to detach a PCI
> device behind a
> >>>>>> translating bridge that uses the current approach should corrupt
> the allocated
> >>>>>> resource ranges in an rman long before my changes.
> >>>>>>
> >>>>>> That said, that doesn't really explain the panic.  Hmm, the panic
> might be because
> >>>>>> for PCI bridge windows the driver now passes RF_ACTIVE and the
> bus_translate_resource
> >>>>>> hack only kicks in the activate_resource method of
> pci_host_generic.c.
> >>>>>>
> >>>>>>> Detail:
> >>>>>>> . . .
> >>>>>>> pcib0: <BCM2838-compatible PCI-express controller> mem
> 0x7d500000-0x7d50930f irq 80,81 on simplebus2
> >>>>>>> pcib0: parsing FDT for ECAM0:
> >>>>>>> pcib0: PCI addr: 0xc0000000, CPU addr: 0x600000000, Size:
> 0x40000000
> >>>>>>
> >>>>>> This indicates this is a translating bus.
> >>>>>>
> >>>>>>> pcib1: <PCI-PCI bridge> irq 91 at device 0.0 on pci0
> >>>>>>> rman_manage_region: <pcib1 bus numbers> request: start 0x1, end 0x1
> >>>>>>> pcib0: rman_reserve_resource: start=0xc0000000, end=0xc00fffff,
> count=0x100000
> >>>>>>> rman_reserve_resource_bound: <PCIe Memory> request: [0xc0000000,
> 0xc00fffff], length 0x100000, flags 102, device pcib1
> >>>>>>> rman_reserve_resource_bound: trying 0xffffffff <0xc0000000,0xfffff>
> >>>>>>> considering [0xc0000000, 0xffffffff]
> >>>>>>> truncated region: [0xc0000000, 0xc00fffff]; size 0x100000
> (requested 0x100000)
> >>>>>>> candidate region: [0xc0000000, 0xc00fffff], size 0x100000
> >>>>>>> allocating from the beginning
> >>>>>>> rman_manage_region: <pcib1 memory window> request: start
> 0x600000000, end 0x6000fffff
> >>>
> >>> What you later typed does not match:
> >>>
> >>> 0x600000000
> >>> 0x6000fffff
> >>>
> >>> You later typed:
> >>>
> >>> 0x60000000
> >>> 0x600fffffff
> >>>
> >>> This seems to have lead to some confusion from using the
> >>> wrong figure(s).
> >>>
> >>>>>> The fact that we are trying to reserve the CPU addresses in the
> rman is because
> >>>>>> bus_translate_resource rewrote the start address in the resource
> after it was allocated.
> >>>>>>
> >>>>>> That said, I can't see why rman_manage_region would actually fail.
> At this point the
> >>>>>> rman is empty (this is the first call to rman_manage_region for
> "pcib1 memory window"),
> >>>>>> so only the check that should be failing are the checks against
> rm_start and
> >>>>>> rm_end.  For the memory window, rm_start is always 0, and rm_end is
> always
> >>>>>> 0xffffffff, so both the old (0xc00000000 - 0xc00fffff) and new
> (0x60000000 - 0x600fffffff)
> >>>>>> ranges are within those bounds.
> >>>
> >>> No:
> >>>
> >>> 0xffffffff
> >>>
> >>> .vs (actual):
> >>>
> >>> 0x600000000
> >>> 0x6000fffff
>
> Ok, then this explains the failure if the "raw" addresses are above 4G.  I
> have
> access to an emag I'm currently using to test fixes to pci_host_generic.c
> to
> avoid corrupting struct resource objects.  I'll post the diff once I've got
> something verified to work.
>
> > It looks to me like in sys/dev/pci/pci_pci.c the:
> >
> > static void
> > pcib_probe_windows(struct pcib_softc *sc)
> > {
> > . . .
> >          pcib_alloc_window(sc, &sc->mem, SYS_RES_MEMORY, 0, 0xffffffff);
> > . . .
> >
> > is just inappropriately restrictive about where in the system
> > address space a PCIe can validly be mapped to on the high end.
> > That, in turn, leads to the rejection on the RPi4B now that
> > the range use is checked.
>
> No, the physical register in PCI-PCI bridges is only 32-bits.  Only the
> prefetchable BAR supports 64-bit addresses.  This is why the host bridge
> is doing a translation from the CPU side (0x600000000) to the PCI BAR
> addresses (0xc0000000) so that the BAR addresses are down in the 32-bit
> address range.  It's also true that many PCI devices only support 32-bit
> addresses in memory BARs.  64-bit BARs are an optional extension not
> universally supported.
>
> The translation here is somewhat akin to a type of MMU where the CPU
> addresses are mapped to PCI addresses.  The problem here is that the
> PCI BAR resources need to "stay" as PCI addresses since we depend on
> being able to use rman_get_start/end to get the PCI addresses of
> allocated resources, but pci_host_generic.c currently rewrites the
> addresses.
>
> Probably I should remove rman_set_start/end entirely (Warner added them
> back in 2004) as the methods don't do anything to deal with the fallout
> that the rman.rm_list linked-list is no longer sorted by address once
> some addresses get rewritten, etc.
>

At the time, they made sense. Removing it, though may take some doing
since we use it in about 284 places  in sys/dev today... Somewhat more
pervasive than I'd have thought they'd be...

Warner