From: "Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>
To: Tudor Ambarus <tudor.ambarus@linaro.org>
Cc: "Bjorn Helgaas" <bhelgaas@google.com>,
linux-pci@vger.kernel.org,
"Michał Winiarski" <michal.winiarski@intel.com>,
"Igor Mammedov" <imammedo@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
"Mika Westerberg" <mika.westerberg@linux.intel.com>,
"William McVicker" <willmcvicker@google.com>
Subject: Re: [PATCH 24/25] PCI: Perform reset_resource() and build fail list in sync
Date: Fri, 30 May 2025 09:38:32 +0300 (EEST) [thread overview]
Message-ID: <f6ee05f7-174b-76d4-3dbe-12473f676e4d@linux.intel.com> (raw)
In-Reply-To: <3a47fc82-dc21-46c3-873d-68e713304af3@linaro.org>
[-- Attachment #1: Type: text/plain, Size: 14908 bytes --]
On Wed, 28 May 2025, Tudor Ambarus wrote:
> On 5/6/25 4:53 PM, Ilpo Järvinen wrote:
> > On Tue, 6 May 2025, Tudor Ambarus wrote:
> >> On 12/16/24 5:56 PM, Ilpo Järvinen wrote:
> >>> Resetting resource is problematic as it prevent attempting to allocate
> >>> the resource later, unless something in between restores the resource.
> >>> Similarly, if fail_head does not contain all resources that were reset,
> >>> those resource cannot be restored later.
> >>>
> >>> The entire reset/restore cycle adds complexity and leaving resources
> >>> into reseted state causes issues to other code such as for checks done
> >>> in pci_enable_resources(). Take a small step towards not resetting
> >>> resources by delaying reset until the end of resource assignment and
> >>> build failure list (fail_head) in sync with the reset to avoid leaving
> >>> behind resources that cannot be restored (for the case where the caller
> >>> provides fail_head in the first place to allow restore somewhere in the
> >>> callchain, as is not all callers pass non-NULL fail_head).
> >>>
> >>> The Expansion ROM check is temporarily left in place while building the
> >>> failure list until the upcoming change which reworks optional resource
> >>> handling.
> >>>
> >>> Ideally, whole resource reset could be removed but doing that in a big
> >>> step would make the impact non-tractable due to complexity of all
> >>> related code.
> >>>
> >>> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> >>
> >> I'm hitting the BUG_ON(!list_empty(&add_list)); in
> >> pci_assign_unassigned_bus_resources() [1] with 6.15-rc5 and the the
> >> pixel6 downstream pcie driver.
> >>
> >> I saw the thread where "a34d74877c66 PCI: Restore assigned resources
> >> fully after release" fixes things for some other cases, but it's not the
> >> case here.
> >>
> >> Reverting the following patches fixes the problem:
> >> a34d74877c66 PCI: Restore assigned resources fully after release
> >> 2499f5348431 PCI: Rework optional resource handling
> >> 96336ec70264 PCI: Perform reset_resource() and build fail list in sync
> >
> > So it's confirmed that you needed to revert also this last commit
> > 96336ec70264, not just the rework change?
>
> I needed to revert 96336ec70264 as well otherwise the build fails.
Hi again,
That's news to me... I seem to have botched the resource assignment rework
series at some point when I reordered patches and dropped that helper as a
result. And it seems the intermediate build fail wasn't caught by LKP :-(.
(Pretty annoying as I intentionally separated these two to make them
bisectable but not it isn't without amends.)
The missing helper is basically this:
static bool pci_resource_is_disabled_rom(const struct pci_dev *dev, int resno)
{
const struct resource *res = pci_resource_n(dev, resno);
return resno == PCI_ROM_RESOURCE && !(res->flags & IORESOURCE_ROM_ENABLE)
}
(I didn't build test that.)
Because of this, the actual culprit could be in 2499f5348431, not it
96336ec70264 (which would make more sense as it does significant rework
on the assignment algorithm).
> >> In the working case the add_list list is empty throughout the entire
> >> body of pci_assign_unassigned_bus_resources().
> >>
> >> In the failing case __pci_bus_size_bridges() leaves the add_list not
> >> empty and __pci_bus_assign_resources() does not consume the list, thus
> >> the BUG_ON. The failing case contains an extra print that's not shown
> >> when reverting the blamed commits:
> >> [ 13.951185][ T1101] pcieport 0000:00:00.0: bridge window [mem
> >> 0x00100000-0x001fffff] to [bus 01-ff] add_size 100000 add_align 100000
> >>
> >> I've added some prints trying to describe the code path, see
> >> https://paste.ofcode.org/Aeu2YBpLztc49ZDw3uUJmd#
> >>
> >> Failing case:
> >> [ 13.944231][ T1101] pci 0000:01:00.0: [144d:a5a5] type 00 class
> >> 0x000000 PCIe Endpoint
> >> [ 13.944412][ T1101] pci 0000:01:00.0: BAR 0 [mem
> >> 0x00000000-0x000fffff 64bit]
> >> [ 13.944532][ T1101] pci 0000:01:00.0: ROM [mem 0x00000000-0x0000ffff
> >> pref]
> >> [ 13.944649][ T1101] pci 0000:01:00.0: enabling Extended Tags
> >> [ 13.944844][ T1101] pci 0000:01:00.0: PME# supported from D0 D3hot D3cold
> >> [ 13.945015][ T1101] pci 0000:01:00.0: 15.752 Gb/s available PCIe
> >> bandwidth, limited by 8.0 GT/s PCIe x2 link at 0000:00:00.0 (capable of
> >> 31.506 Gb/s with 16.0 GT/s PCIe x2 link)
> >> [ 13.950616][ T1101] __pci_bus_size_bridges: before pbus_size_mem.
> >> list empty? 1
> >> [ 13.950784][ T1101] pbus_size_mem: 2. list empty? 1
> >> [ 13.950886][ T1101] pbus_size_mem: 1 list empty? 0
> >> [ 13.950982][ T1101] pbus_size_mem: 3. list empty? 0
> >> [ 13.951082][ T1101] pbus_size_mem: 4. list empty? 0
> >> [ 13.951185][ T1101] pcieport 0000:00:00.0: bridge window [mem
> >> 0x00100000-0x001fffff] to [bus 01-ff] add_size 100000 add_align 100000
> >> [ 13.951448][ T1101] __pci_bus_size_bridges: after pbus_size_mem. list
> >> empty? 0
> >> [ 13.951643][ T1101] pci_assign_unassigned_bus_resources: before
> >> __pci_bus_assign_resources -> list empty? 0
> >> [ 13.951924][ T1101] pcieport 0000:00:00.0: bridge window [mem
> >> 0x40000000-0x401fffff]: assigned
> >> [ 13.952248][ T1101] pci_assign_unassigned_bus_resources: after
> >> __pci_bus_assign_resources -> list empty? 0
> >> [ 13.952634][ T1101] ------------[ cut here ]------------
> >> [ 13.952818][ T1101] kernel BUG at drivers/pci/setup-bus.c:2514!
> >> [ 13.953045][ T1101] Internal error: Oops - BUG: 00000000f2000800 [#1]
> >> SMP
> >> ...
> >> [ 13.976086][ T1101] Call trace:
> >> [ 13.976206][ T1101] pci_assign_unassigned_bus_resources+0x110/0x114 (P)
> >> [ 13.976462][ T1101] pci_rescan_bus+0x28/0x48
> >> [ 13.976628][ T1101] exynos_pcie_rc_poweron
> >>
> >> Working case:
> >> [ 13.786961][ T1120] pci 0000:01:00.0: [144d:a5a5] type 00 class
> >> 0x000000 PCIe Endpoint
> >> [ 13.787136][ T1120] pci 0000:01:00.0: BAR 0 [mem
> >> 0x00000000-0x000fffff 64bit]
> >> [ 13.787280][ T1120] pci 0000:01:00.0: ROM [mem 0x00000000-0x0000ffff
> >> pref]
> >> [ 13.787541][ T1120] pci 0000:01:00.0: enabling Extended Tags
> >> [ 13.787808][ T1120] pci 0000:01:00.0: PME# supported from D0 D3hot D3cold
> >> [ 13.787988][ T1120] pci 0000:01:00.0: 15.752 Gb/s available PCIe
> >> bandwidth, limited by 8.0 GT/s PCIe x2 link at 0000:00:00.0 (capable of
> >> 31.506 Gb/s with 16.0 GT/s PCIe x2 link)
> >> [ 13.795279][ T1120] __pci_bus_size_bridges: before pbus_size_mem.
> >> list empty? 1
> >> [ 13.795408][ T1120] pbus_size_mem: 2. list empty? 1
> >> [ 13.795495][ T1120] pbus_size_mem: 2. list empty? 1
> >> [ 13.795577][ T1120] __pci_bus_size_bridges: after pbus_size_mem. list
> >> empty? 1
> >> [ 13.795692][ T1120] pci_assign_unassigned_bus_resources: before
> >> __pci_bus_assign_resources -> list empty? 1
> >> [ 13.795849][ T1120] pcieport 0000:00:00.0: bridge window [mem
> >> 0x40000000-0x401fffff]: assigned
> >> [ 13.796072][ T1120] pci_assign_unassigned_bus_resources: after
> >> __pci_bus_assign_resources -> list empty? 1
> >> [ 13.796662][ T1120] cpif: s5100_poweron_pcie: DBG: MSI sfr not set
> >> up, yet(s5100_pdev is NULL)
> >> [ 13.796666][ T1120] cpif: register_pcie: s51xx_pcie_init start
> >>
> >>
> >> Any hints are welcomed. Thanks,
> >> ta
> >
> > Hi and thanks for the report.
>
> Hi! Thanks for the help. I've been out of office for the last 2 weeks,
> sorry for the delayed reply.
Np.
> > The interesting part occurs inside reassign_resources_sorted() where most
> > items are eliminated from realloc_head by the list_del().
> >
> > My guess is that somehow, the change in 96336ec70264 from !res->flags
> > to the more complicated check somehow causes this. If the new check
> > doesn't match and subsequently, no match is found from the head list, the
> > loop will do continue and not remove the entry from realloc_head.
>
> I added a print right there and it seems it's something else. See below.
> >
> > But it's hard to confirm without knowing what that resources realloc_head
> > contains. Perhaps if you print the resources that are processed around
> > that part of the code in reassign_resources_sorted(), comparing the log
> > from the reverted code with the non-working case might help to understand
> > what is different there and why. To understand better what is in the head
> > list, it would be also useful to know from which device the resources were
> > added into the head list in pdev_sort_resources().
> >
>
> I added the suggested prints
> (https://paste.ofcode.org/DgmZGGgS6D36nWEzmfCqMm) on top of v6.15 with
> the downstream PCIe pixel driver and I obtain the following. Note that
> all added prints contain "tudor" for differentiation.
>
> [ 15.211179][ T1107] pci 0001:01:00.0: [144d:a5a5] type 00 class
> 0x000000 PCIe Endpoint
> [ 15.212248][ T1107] pci 0001:01:00.0: BAR 0 [mem
> 0x00000000-0x000fffff 64bit]
> [ 15.212775][ T1107] pci 0001:01:00.0: ROM [mem 0x00000000-0x0000ffff
> pref]
> [ 15.213195][ T1107] pci 0001:01:00.0: enabling Extended Tags
> [ 15.213720][ T1107] pci 0001:01:00.0: PME# supported from D0 D3hot
> D3cold
> [ 15.214035][ T1107] pci 0001:01:00.0: 15.752 Gb/s available PCIe
> bandwidth, limited by 8.0 GT/s PCIe x2 link at 0001:00:00.0 (capable of
> 31.506 Gb/s with 16.0 GT/s PCIe x2 link)
> [ 15.222286][ T1107] pci 0001:01:00.0: tudor: 1: pbus_size_mem: BAR 0
> [mem 0x00000000-0x000fffff 64bit] list empty? 1
> [ 15.222813][ T1107] pci 0001:01:00.0: tudor: 1: pbus_size_mem: ROM
> [mem 0x00000000-0x0000ffff pref] list empty? 1
> [ 15.224429][ T1107] pci 0001:01:00.0: tudor: 2: pbus_size_mem: ROM
> [mem 0x00000000-0x0000ffff pref] list empty? 0
> [ 15.224750][ T1107] pcieport 0001:00:00.0: bridge window [mem
> 0x00100000-0x001fffff] to [bus 01-ff] add_size 100000 add_align 100000
>
> [ 15.225393][ T1107] tudor : pci_assign_unassigned_bus_resources:
> before __pci_bus_assign_resources -> list empty? 0
> [ 15.225594][ T1107] pcieport 0001:00:00.0: tudor:
> pdev_sort_resources: bridge window [mem 0x00100000-0x001fffff] resource
> added in head list
> [ 15.226078][ T1107] pcieport 0001:00:00.0: bridge window [mem
> 0x40000000-0x401fffff]: assigned
So here it ends up assigning the resource here I think.
That print isn't one of yours in reassign_resources_sorted() so the
assignment must have been made in assign_requested_resources_sorted(). But
then nothing is printed out from reassign_resources_sorted() so I suspect
__assign_resources_sorted() has short-circuited.
We know that realloc_head is not empty, so that leaves the goto out from
if (list_empty(&local_fail_head)), which kind of makes sense, all
entries on the head list were assigned. But the code there tries to remove
all head list resources from realloc_head so why it doesn't get removed is
still a mystery. assign_requested_resources_sorted() doesn't seem to
remove anything from the head list so that resource should still be on the
head list AFAICT so it should call that remove_from_list(realloc_head,
dev_res->res) for it.
So can you see if that theory holds water and it short-circuits without
removing the entry from realloc_head?
> [ 15.226419][ T1107] tudor : pci_assign_unassigned_bus_resources:
> after __pci_bus_assign_resources -> list empty? 0
> [ 15.226442][ T1107] ------------[ cut here ]------------
> [ 15.227587][ T1107] kernel BUG at drivers/pci/setup-bus.c:2522!
> [ 15.227813][ T1107] Internal error: Oops - BUG: 00000000f2000800 [#1]
> SMP
> ...
> [ 15.251570][ T1107] Call trace:
> [ 15.251690][ T1107] pci_assign_unassigned_bus_resources+0x110/0x114 (P)
> [ 15.251945][ T1107] pci_rescan_bus+0x28/0x48
>
> I obtain the following output when using the same prints adapted
> (https://paste.ofcode.org/37w7RnKkPaCxyNhi5yhZPbZ) and with the blamed
> commits reverted:
> a34d74877c66 PCI: Restore assigned resources fully after release
> 2499f5348431 PCI: Rework optional resource handling
> 96336ec70264 PCI: Perform reset_resource() and build fail list in sync
>
> [ 15.200456][ T1102] pci 0000:01:00.0: [144d:a5a5] type 00 class
> 0x000000 PCIe Endpoint
> [ 15.200632][ T1102] pci 0000:01:00.0: BAR 0 [mem
> 0x00000000-0x000fffff 64bit]
> [ 15.200755][ T1102] pci 0000:01:00.0: ROM [mem 0x00000000-0x0000ffff
> pref]
> [ 15.200876][ T1102] pci 0000:01:00.0: enabling Extended Tags
> [ 15.201075][ T1102] pci 0000:01:00.0: PME# supported from D0 D3hot D3cold
> [ 15.201254][ T1102] pci 0000:01:00.0: 15.752 Gb/s available PCIe
> bandwidth, limited by 8.0 GT/s PCIe x2 link at 0000:00:00.0 (capable of
> 31.506 Gb/s with 16.0 GT/s PCIe x2 link)
> [ 15.206555][ T1102] pci 0000:01:00.0: tudor: 1: pbus_size_mem: BAR 0
> [mem 0x00000000-0x000fffff 64bit] list empty? 1
> [ 15.206737][ T1102] pci 0000:01:00.0: tudor: 1: pbus_size_mem: ROM
> [mem 0x00000000-0x0000ffff pref] list empty? 1
> [ 15.206901][ T1102] tudor : pci_assign_unassigned_bus_resources:
> before __pci_bus_assign_resources -> list empty? 1
> [ 15.207072][ T1102] pcieport 0000:00:00.0: tudor:
> pdev_sort_resources: bridge window [mem 0x00100000-0x002fffff] resource
> added in head list
> [ 15.207396][ T1102] pcieport 0000:00:00.0: bridge window [mem
> 0x40000000-0x401fffff]: assigned
> [ 15.208165][ T1102] tudor : pci_assign_unassigned_bus_resources:
> after __pci_bus_assign_resources -> list empty? 1
> [ 15.208783][ T1102] cpif: s5100_poweron_pcie: DBG: MSI sfr not set
> up, yet(s5100_pdev is NULL)
> [ 15.208786][ T1102] cpif: register_pcie: s51xx_pcie_init start
>
> > In any case, that BUG_ON() seems a bit drastic action for what might be
> > just a single resource allocation failure so it should be downgraded to:
> >
> > if (WARN_ON(!list_empty(&add_list))
> > free_list(&add_list);
> >
> > ... or WARN_ON_ONCE().
>
> I saw your patch doing this, the phone now boots, but obviously I still
> see the WARN, so maybe there's still something to be fixed.
Yes, I don't expect BUG_ON() -> WARN "fix" anything, it just downgrades
the severity so that the system can still try to boot, which can often
succeed as this tends to be non-critical failure in many cases so it's
useful change to have regardless despite the splat.
Now that it boots, can you please check if /proc/iomem is the same both in
the non-working and working config. If that resource got assigned
successfully, it might well be there is no actual differences in the
assigned resources (which again doesn't mean there wouldn't be a bug in
the logic as discussed above).
--
i.
next prev parent reply other threads:[~2025-05-30 6:38 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-12-16 17:56 [PATCH 00/25] PCI: Resource fitting/assignment fixes and cleanups Ilpo Järvinen
2025-02-14 9:59 ` Xiaochun Lee
2024-12-16 17:56 ` [PATCH 01/25] PCI: Remove add_align overwrite unrelated to size0 Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 02/25] PCI: size0 is unrelated to add_align Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 03/25] PCI: Simplify size1 assignment logic Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 04/25] PCI: Optional bridge window size too may need relaxing Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 05/25] PCI: Fix old_size lower bound in calculate_iosize() too Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 06/25] PCI: Use SZ_* instead of literals in setup-bus.c Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 07/25] PCI: resource_set_range/size() conversions Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 08/25] PCI: Add a helper to identify IOV resources Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 09/25] PCI: Check resource_size() separately Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 10/25] PCI: Add pci_resource_num() helper Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 11/25] PCI: Add dev & res local variables to resource assignment funcs Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 12/25] PCI: Converge return paths in __assign_resources_sorted() Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 13/25] PCI: Refactor pdev_sort_resources() & __dev_sort_resources() Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 14/25] PCI: Use while loop and break instead of gotos Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 15/25] PCI: Rename retval to ret Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 16/25] PCI: Consolidate assignment loop next round preparation Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 17/25] PCI: Remove wrong comment from pci_reassign_resource() Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 18/25] PCI: Add restore_dev_resource() Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 19/25] PCI: Extend enable to check for any optional resource Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 20/25] PCI: Always have realloc_head in __assign_resources_sorted() Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 21/25] PCI: Indicate optional resource assignment failures Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 22/25] PCI: Add debug print when releasing resources before retry Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 23/25] PCI: Use res->parent to check is resource is assigned Ilpo Järvinen
2024-12-16 17:56 ` [PATCH 24/25] PCI: Perform reset_resource() and build fail list in sync Ilpo Järvinen
2025-04-01 2:35 ` Guenter Roeck
2025-04-01 10:18 ` Ilpo Järvinen
2025-04-01 12:07 ` Ilpo Järvinen
2025-04-01 14:15 ` Guenter Roeck
2025-04-01 17:38 ` Ilpo Järvinen
2025-04-11 19:37 ` Ondřej Jirman
2025-04-14 9:52 ` Ilpo Järvinen
2025-04-14 12:19 ` Ondřej Jirman
2025-04-14 13:15 ` Ilpo Järvinen
2025-04-14 13:43 ` Ondřej Jirman
2025-04-14 13:52 ` Ilpo Järvinen
2025-04-01 13:28 ` Guenter Roeck
2025-05-06 15:03 ` Tudor Ambarus
2025-05-06 15:53 ` Ilpo Järvinen
2025-05-28 11:22 ` Tudor Ambarus
2025-05-28 11:39 ` Tudor Ambarus
2025-05-28 13:09 ` Tudor Ambarus
2025-05-30 6:55 ` Ilpo Järvinen
2025-05-30 6:38 ` Ilpo Järvinen [this message]
2025-05-30 14:48 ` Ilpo Järvinen
2025-06-02 14:40 ` Tudor Ambarus
2025-06-02 15:08 ` Ilpo Järvinen
2025-06-02 18:42 ` Tudor Ambarus
2025-06-03 8:13 ` Ilpo Järvinen
2025-06-03 10:36 ` Tudor Ambarus
2025-06-03 10:48 ` Tudor Ambarus
2025-06-03 11:43 ` Tudor Ambarus
2025-06-03 14:23 ` Ilpo Järvinen
2025-06-03 14:43 ` Ilpo Järvinen
2025-06-03 14:13 ` Ilpo Järvinen
2025-06-03 15:25 ` Tudor Ambarus
2025-06-03 17:03 ` Ilpo Järvinen
2025-06-03 17:09 ` Ilpo Järvinen
2025-06-02 12:32 ` Tudor Ambarus
2025-06-19 0:30 ` D Scott Phillips
2025-06-24 12:48 ` Ilpo Järvinen
2025-06-25 17:45 ` Ilpo Järvinen
2025-06-25 20:33 ` D Scott Phillips
2025-06-26 9:22 ` Ilpo Järvinen
2025-06-26 14:53 ` D Scott Phillips
2024-12-16 17:56 ` [PATCH 25/25] PCI: Rework optional resource handling Ilpo Järvinen
2025-02-13 21:46 ` [PATCH 00/25] PCI: Resource fitting/assignment fixes and cleanups Bjorn Helgaas
2025-02-14 8:18 ` Xiaochun XC17 Li | 李小春 Xavier
2025-02-14 11:53 ` Ilpo Järvinen
2025-02-14 21:28 ` Bjorn Helgaas
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