Date: Mon, 12 Feb 2024 10:41:55 -0800 From: Mark Millard <marklmi@yahoo.com> To: John Baldwin <jhb@freebsd.org> Cc: FreeBSD ARM List <freebsd-arm@freebsd.org>, Current FreeBSD <freebsd-current@freebsd.org>, Warner Losh <imp@bsdimp.com> Subject: Re: Recent commits reject RPi4B booting: pcib0 vs. pcib1 "rman_manage_region: <pcib1 memory window> request" leads to panic Message-ID: <1F704317-FDB8-4BDA-8A67-61CF48794DFE@yahoo.com> In-Reply-To: <f4326cda-c602-439f-ab03-f66b3bca5ff2@FreeBSD.org> References: <76AB969F-5BC5-4116-8AF4-3ED2CABEBBA5.ref@yahoo.com> <76AB969F-5BC5-4116-8AF4-3ED2CABEBBA5@yahoo.com> <f4326cda-c602-439f-ab03-f66b3bca5ff2@FreeBSD.org>
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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
>=20
> 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.
>=20
> 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.
>=20
>> 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
>=20
> This indicates this is a translating bus.
>=20
>> 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=3D0xc0000000, end=3D0xc00fffff, =
count=3D0x100000
>> 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
>=20
> 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.
>=20
> 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. I would instead expect to see some =
other issue later
> on where we fail to allocate a resource for a child BAR, but I =
wouldn't expect
> rman_manage_region to fail.
>=20
> Logging the return value from rman_manage_region would be the first =
step I think
> to see which error value it is returning.
Looking at the code in sys/kern/subr_rman.c for rman_manage_region I see
the (mostly) return rv related logic only has ENONMEM (explicit return) =
and
EBUSY as non-0 possibilities (no other returns). All the rv references =
and
all the returns are shown below:
int rv =3D 0;
. . .
r =3D int_alloc_resource(M_NOWAIT);
if (r =3D=3D NULL)
return ENOMEM;
. . .
/* Check for any overlap with the current region. */
if (r->r_start <=3D s->r_end && r->r_end >=3D =
s->r_start) {
rv =3D EBUSY;
goto out;
}
/* Check for any overlap with the next region. */
t =3D TAILQ_NEXT(s, r_link);
if (t && r->r_start <=3D t->r_end && r->r_end >=3D =
t->r_start) {
rv =3D EBUSY;
goto out;
}
. . .
out:
mtx_unlock(rm->rm_mtx);
return rv;
int_alloc_resource failure would be failure (NULL) from the:
struct resource_i *r;
=20
r =3D malloc(sizeof *r, M_RMAN, malloc_flag | M_ZERO);
(associated with the M_NOWAIT argument).
The malloc failure would likely go in a very different direction.
Side note: looks like the EBUSY cases leak what r references.
> Probably I should fix pci_host_generic.c to handle translation =
properly however.
> I can work on a patch for that.
=3D=3D=3D
Mark Millard
marklmi at yahoo.com
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