RE: [PATCH V2] pci: introduce static_nr to indicate domain_nr from which IDA

From: Peng Fan
Date: Tue Sep 12 2023 - 22:49:44 EST

Next message: Chen Yu: "Re: [RFC PATCH 2/2] sched/fair: skip the cache hot CPU in select_idle_cpu()"
Previous message: Moudy Ho (何宗原): "Re: [PATCH v5 02/14] arm64: dts: mediatek: mt8195: add MDP3 nodes"
In reply to: Bjorn Helgaas: "Re: [PATCH V2] pci: introduce static_nr to indicate domain_nr from which IDA"
Next in thread: Bjorn Helgaas: "Re: [PATCH V2] pci: introduce static_nr to indicate domain_nr from which IDA"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

> Subject: Re: [PATCH V2] pci: introduce static_nr to indicate domain_nr from
> which IDA
>
> On Wed, Sep 13, 2023 at 01:24:26AM +0000, Peng Fan wrote:
> > > Subject: Re: [PATCH V2] pci: introduce static_nr to indicate
> > > domain_nr from which IDA
> > >
> > > On Tue, Aug 15, 2023 at 09:37:44AM +0800, Peng Fan (OSS) wrote:
> > > > From: Peng Fan <peng.fan@xxxxxxx>
> > > >
> > > > When PCI node was created using an overlay and the overlay is
> > > > reverted/destroyed, the "linux,pci-domain" property no longer
> > > > exists, so of_get_pci_domain_nr will return failure.
> > >
> > > I'm not familiar with how overlays work. What's the call path where
> > > the overlay is removed? I see an of_overlay_remove(), but I don't
> > > see any callers except test cases.
> >
> > We are using an out of tree hypervisor driver:
> > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgith
> >
> ub.com%2Fsiemens%2Fjailhouse%2Fblob%2Fmaster%2Fdriver%2Fpci.c%23L
> 483&d
> >
> ata=05%7C01%7Cpeng.fan%40nxp.com%7C1bf0364c585f42dae7f108dbb3fe
> fcc4%7C
> >
> 686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C63830167996269745
> 6%7CUnknow
> >
> n%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1ha
> WwiLC
> >
> JXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=raIsz2HIH%2FQ0nmolBBwd81
> WxQh2vmFeXN
> > t3n6OIQaSU%3D&reserved=0
> > >
> > > I guess the problem happens in a PCI host bridge remove path, e.g.,
> > >
> > > pci_host_common_remove
> > > pci_remove_root_bus
> > > pci_bus_release_domain_nr
> > > of_pci_bus_release_domain_nr
> > >
> > > But I don't know how that's related to the overlay removal.
> >
> > When the overlay node got removed, the device removal will be invoked
> > and the domain number indicated by linux,pci-domain should also get freed.
> >
> > But actually the domain number not got freed because of bug as this
> > patch shows. "of_pci_bus_release_domain_nr will actually use the
> > dynamic IDA, even if the IDA was allocated in static IDA."
> >
> > So after the overlay node got destroyed and our test recreate the
> > overlay node with same domain number, issue triggered, the device
> > could not be created.
> >
> > > Is this an ordering issue? It seems possibly problematic that the
> > > OF overlay is destroyed before the device it describes (e.g., the
> > > host
> >
> > No. it is "of_pci_bus_release_domain_nr will actually use the dynamic
> > IDA, even if the IDA was allocated in static IDA "
>
> Yes, that's the *symptom*, to be sure. My question was why the overlay was
> removed before the host bridge.

I am not sure.
I added a dump_stack, would this help to understand?
root@imx93evk:~# jailhouse disable
[ 595.150529] CPU: 1 PID: 582 Comm: jailhouse Tainted: G O 6.5.0-rc4-next-20230804-05021-g3d4cc14b42ef-dirty #355
[ 595.161998] Hardware name: NXP i.MX93 11X11 EVK board (DT)
[ 595.167475] Call trace:
[ 595.169908] dump_backtrace+0x94/0xec
[ 595.173573] show_stack+0x18/0x24
[ 595.176884] dump_stack_lvl+0x48/0x60
[ 595.180541] dump_stack+0x18/0x24
[ 595.183843] pci_bus_release_domain_nr+0x34/0x84
[ 595.188453] pci_remove_root_bus+0xa0/0xa4
[ 595.192544] pci_host_common_remove+0x28/0x40
[ 595.196895] platform_remove+0x54/0x6c
[ 595.200641] device_remove+0x4c/0x80
[ 595.204209] device_release_driver_internal+0x1d4/0x230
[ 595.209430] device_release_driver+0x18/0x24
[ 595.213691] bus_remove_device+0xcc/0x10c
[ 595.217686] device_del+0x15c/0x41c
[ 595.221170] platform_device_del.part.0+0x1c/0x88
[ 595.225861] platform_device_unregister+0x24/0x40
[ 595.230557] of_platform_device_destroy+0xfc/0x10c
[ 595.235344] of_platform_notify+0x13c/0x178
[ 595.239518] blocking_notifier_call_chain+0x6c/0xa0
[ 595.244389] __of_changeset_entry_notify+0x148/0x16c
[ 595.249346] of_changeset_revert+0xa8/0xcc
[ 595.253437] jailhouse_pci_virtual_root_devices_remove+0x50/0x74 [jailhouse]
[ 595.260484] jailhouse_cmd_disable+0x70/0x1ac [jailhouse]
[ 595.265883] jailhouse_ioctl+0x60/0xf0 [jailhouse]
[ 595.270674] __arm64_sys_ioctl+0xac/0xf0
[ 595.274595] invoke_syscall+0x48/0x114
[ 595.278336] el0_svc_common.constprop.0+0xc4/0xe4
>
> The current ordering is this, where A happens before B:
>
> A overlay is removed
> B pci_host_common_remove
> pci_bus_release_domain_nr
> of_pci_bus_release_domain_nr
> of_get_pci_domain_nr # fails because overlay is gone
> ida_free(&pci_domain_nr_dynamic_ida)
>
> But if the host bridge were removed first, the ordering would be as follows,
> and the problem would not occur:
>
> B pci_host_common_remove
> pci_bus_release_domain_nr
> of_pci_bus_release_domain_nr
> of_get_pci_domain_nr # succeeds in this order
> ida_free(&pci_domain_nr_static_ida)
> A overlay is removed
>
> Is there a reason the overlay should be removed before the host bridge?
>
> Obviously the overlay is loaded before the host bridge is created, and
> symmetry would suggest that the overlay should be removed after the host
> bridge is removed.

Hmm, I need check more. But do you think this patch is fix a real issue or
If order is did as you say above, this patch is not required anymore?

Thanks,
Peng.

>
> > > bridge) is removed. I would expect the device to be removed before
> > > the description of the device is removed.
> > >
> > > > Then of_pci_bus_release_domain_nr will actually use the dynamic
> > > > IDA, even if the IDA was allocated in static IDA.
> > > >
> > > > Introduce a static_nr field in pci_bus to indicate whether the IDA
> > > > is a dynamic or static in order to free the correct one.
> > > >
> > > > Fixes: c14f7ccc9f5d ("PCI: Assign PCI domain IDs by ida_alloc()")
> > > > Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
> > > > ---
> > > >
> > > > V2:
> > > > Update commit message
> > > > Move static_nr:1 to stay besides others :1 fields.
> > > >
> > > > drivers/pci/pci.c | 22 ++++++++++++++--------
> > > > include/linux/pci.h | 1 +
> > > > 2 files changed, 15 insertions(+), 8 deletions(-)
> > > >
> > > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index
> > > > 60230da957e0..5c98502bcda6 100644
> > > > --- a/drivers/pci/pci.c
> > > > +++ b/drivers/pci/pci.c
> > > > @@ -6881,10 +6881,10 @@ static void
> > > of_pci_reserve_static_domain_nr(void)
> > > > }
> > > > }
> > > >
> > > > -static int of_pci_bus_find_domain_nr(struct device *parent)
> > > > +static int of_pci_bus_find_domain_nr(struct pci_bus *bus, struct
> > > > +device *parent)
> > > > {
> > > > static bool static_domains_reserved = false;
> > > > - int domain_nr;
> > > > + int domain_nr, ret;
> > > >
> > > > /* On the first call scan device tree for static allocations. */
> > > > if (!static_domains_reserved) {
> > > > @@ -6892,6 +6892,8 @@ static int of_pci_bus_find_domain_nr(struct
> > > device *parent)
> > > > static_domains_reserved = true;
> > > > }
> > > >
> > > > + bus->static_nr = 0;
> > > > +
> > > > if (parent) {
> > > > /*
> > > > * If domain is in DT, allocate it in static IDA. This @@ -
> > > 6899,10
> > > > +6901,14 @@ static int of_pci_bus_find_domain_nr(struct device
> > > > +*parent)
> > > > * in DT.
> > > > */
> > > > domain_nr = of_get_pci_domain_nr(parent->of_node);
> > > > - if (domain_nr >= 0)
> > > > - return ida_alloc_range(&pci_domain_nr_static_ida,
> > > > - domain_nr, domain_nr,
> > > > - GFP_KERNEL);
> > > > + if (domain_nr >= 0) {
> > > > + ret = ida_alloc_range(&pci_domain_nr_static_ida,
> > > > + domain_nr, domain_nr,
> > > GFP_KERNEL);
> > > > + if (ret >= 0)
> > > > + bus->static_nr = 1;
> > > > +
> > > > + return ret;
> > > > + }
> > > > }
> > > >
> > > > /*
> > > > @@ -6920,7 +6926,7 @@ static void
> > > > of_pci_bus_release_domain_nr(struct
> > > pci_bus *bus, struct device *par
> > > > return;
> > > >
> > > > /* Release domain from IDA where it was allocated. */
> > > > - if (of_get_pci_domain_nr(parent->of_node) == bus->domain_nr)
> > > > + if (bus->static_nr)
> > > > ida_free(&pci_domain_nr_static_ida, bus->domain_nr);
> > > > else
> > > > ida_free(&pci_domain_nr_dynamic_ida, bus->domain_nr);
> > > @@ -6928,7
> > > > +6934,7 @@ static void of_pci_bus_release_domain_nr(struct pci_bus
> > > > *bus, struct device *par
> > > >
> > > > int pci_bus_find_domain_nr(struct pci_bus *bus, struct device
> > > > *parent) {
> > > > - return acpi_disabled ? of_pci_bus_find_domain_nr(parent) :
> > > > + return acpi_disabled ? of_pci_bus_find_domain_nr(bus, parent) :
> > > > acpi_pci_bus_find_domain_nr(bus); }
> > > >
> > > > diff --git a/include/linux/pci.h b/include/linux/pci.h index
> > > > eeb2e6f6130f..222a1729ea7e 100644
> > > > --- a/include/linux/pci.h
> > > > +++ b/include/linux/pci.h
> > > > @@ -677,6 +677,7 @@ struct pci_bus {
> > > > struct bin_attribute *legacy_mem; /* Legacy mem */
> > > > unsigned int is_added:1;
> > > > unsigned int unsafe_warn:1; /* warned about RW1C
> > > config write */
> > > > + unsigned int static_nr:1;
> > > > };
> > > >
> > > > #define to_pci_bus(n) container_of(n, struct pci_bus, dev)
> > > > --
> > > > 2.37.1
> > > >

Next message: Chen Yu: "Re: [RFC PATCH 2/2] sched/fair: skip the cache hot CPU in select_idle_cpu()"
Previous message: Moudy Ho (何宗原): "Re: [PATCH v5 02/14] arm64: dts: mediatek: mt8195: add MDP3 nodes"
In reply to: Bjorn Helgaas: "Re: [PATCH V2] pci: introduce static_nr to indicate domain_nr from which IDA"
Next in thread: Bjorn Helgaas: "Re: [PATCH V2] pci: introduce static_nr to indicate domain_nr from which IDA"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]