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Date: Fri, 4 Oct 2013 02:18:06 +0100
From: Hedi Berriche <hedi@....com>
To: linux-pci@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, Ethan Zhao <ethan.zhao@...cle.com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Yinghai Lu <yinghai@...nel.org>
Subject: Commit 07f9b61 breaks systems that don't implement a _CBA method
Chaps,
The following failure was encountered on hardware that does *not*
implement a _CBA method which is AFAICT (and confirmed to me by BIOS
chaps) optional.
[ 1.230647] PCI: MMCONFIG for domain 0000 [bus 00-0c] at [mem 0x80000000-0x80cfffff] (base 0x80000000)
[ 1.241046] PCI: MMCONFIG for domain 0001 [bus 00-02] at [mem 0xff84000000-0xff842fffff] (base 0xff84000000)
[ 1.252025] PCI: MMCONFIG for domain 1000 [bus 3f-3f] at [mem 0xff83f00000-0xff83ffffff] (base 0xff80000000)
[ 1.263006] PCI: MMCONFIG for domain 1001 [bus 3f-3f] at [mem 0xff87f00000-0xff87ffffff] (base 0xff84000000)
[ 1.273984] PCI: MMCONFIG at [mem 0x80000000-0x80cfffff] reserved in E820
[ 1.281564] PCI: MMCONFIG at [mem 0xff84000000-0xff842fffff] reserved in E820
[ 1.289535] PCI: MMCONFIG at [mem 0xff83f00000-0xff83ffffff] reserved in E820
[ 1.297505] PCI: MMCONFIG at [mem 0xff87f00000-0xff87ffffff] reserved in E820
<snip>
[ 1.427926] ACPI: PCI Root Bridge [I001] (domain 0001 [bus 00-3d])
[ 1.434968] acpi PNP0A08:00: fail to add MMCONFIG information, can't access PCI configuration space under this host bridge.
[ 1.447405] acpi PNP0A08:00: Bus 0001:00 not present in PCI namespace
...
[ 1.454608] ACPI: PCI Root Bridge [S000] (domain 1000 [bus 3f])
[ 1.461300] acpi PNP0A08:01: fail to add MMCONFIG information, can't access PCI configuration space under this host bridge.
[ 1.473735] acpi PNP0A08:01: Bus 1000:3f not present in PCI namespace
...
[ 1.480935] ACPI: PCI Root Bridge [S001] (domain 1001 [bus 3f])
[ 1.487630] acpi PNP0A08:02: fail to add MMCONFIG information, can't access PCI configuration space under this host bridge.
[ 1.500066] acpi PNP0A08:02: Bus 1001:3f not present in PCI namespace
Bisection points to this commit (included in full given its brevity):
commit 07f9b61c3915e8eb156cb4461b3946736356ad02
Author: ethan.zhao <ethan.zhao@...cle.com>
Date: Fri Jul 26 11:21:24 2013 -0600
x86/PCI: MMCONFIG: Check earlier for MMCONFIG region at address zero
We can check for addr being zero earlier and thus avoid the mutex_unlock()
cleanup path.
[bhelgaas: drop warning printk]
Signed-off-by: ethan.zhao <ethan.zhao@...cle.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
Acked-by: Yinghai Lu <yinghai@...nel.org>
diff --git a/arch/x86/pci/mmconfig-shared.c b/arch/x86/pci/mmconfig-shared.c
index 082e881..5596c7b 100644
--- a/arch/x86/pci/mmconfig-shared.c
+++ b/arch/x86/pci/mmconfig-shared.c
@@ -700,7 +700,7 @@ int pci_mmconfig_insert(struct device *dev, u16 seg, u8 start, u8 end,
if (!(pci_probe & PCI_PROBE_MMCONF) || pci_mmcfg_arch_init_failed)
return -ENODEV;
- if (start > end)
+ if (start > end || !addr)
return -EINVAL;
mutex_lock(&pci_mmcfg_lock);
@@ -716,11 +716,6 @@ int pci_mmconfig_insert(struct device *dev, u16 seg, u8 start, u8 end,
return -EEXIST;
}
- if (!addr) {
- mutex_unlock(&pci_mmcfg_lock);
- return -EINVAL;
- }
-
rc = -EBUSY;
cfg = pci_mmconfig_alloc(seg, start, end, addr);
if (cfg == NULL) {
With this change in place, pci_mmconfig_insert(), when called with addr==0
bails out (too) early with -EINVAL and no longer calls into pci_mmconfig_lookup():
693 int pci_mmconfig_insert(struct device *dev, u16 seg, u8 start, u8 end,
694 phys_addr_t addr)
695 {
696 int rc;
697 struct resource *tmp = NULL;
698 struct pci_mmcfg_region *cfg;
699
700 if (!(pci_probe & PCI_PROBE_MMCONF) || pci_mmcfg_arch_init_failed)
701 return -ENODEV;
702
703 if (start > end || !addr)
704 return -EINVAL;
705
706 mutex_lock(&pci_mmcfg_lock);
707 cfg = pci_mmconfig_lookup(seg, start);
708 if (cfg) {
709 if (cfg->end_bus < end)
710 dev_info(dev, FW_INFO
711 "MMCONFIG for "
712 "domain %04x [bus %02x-%02x] "
713 "only partially covers this bridge\n",
714 cfg->segment, cfg->start_bus, cfg->end_bus);
715 mutex_unlock(&pci_mmcfg_lock);
716 return -EEXIST;
717 }
And given the code path reads:
pci_acpi_scan_root()
setup_mcfg_map()
pci_mmconfig_insert()
this causes setup_mcfg_map() to fail and go down the check_segment() error
path:
171 static int setup_mcfg_map(struct pci_root_info *info, u16 seg, u8 start,
172 u8 end, phys_addr_t addr)
173 {
...
188 result = pci_mmconfig_insert(dev, seg, start, end, addr);
189 if (result == 0) {
...
194 } else if (result != -EEXIST)
195 return check_segment(seg, dev,
196 "fail to add MMCONFIG information,");
197
198 return 0;
199 }
and this finally causes pci_acpi_scan_root() to skip calling pci_create_root_bus()
and all is doom and gloom:
473 struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
474 {
...
550 if (!setup_mcfg_map(info, domain, (u8)root->secondary.start,
551 (u8)root->secondary.end, root->mcfg_addr))
552 bus = pci_create_root_bus(NULL, busnum, &pci_root_ops,
553 sd, &resources);
Before the early !addr check came around, pci_mmconfig_insert() used to be allowed to
call into pci_mmconfig_lookup() which, on the HW affected by this problem, finds an
MMCONFIG that *partially* covers the bridge, and causes pci_mmconfig_insert() to return
with an -EEXIST.
-EEXIST doesn't cause setup_mcfg_map() to fail, pci_acpi_scan_root() then
proceeds and calls pci_create_root_bus().
Where does the _CBA method fit in all of this? it's merely because addr will be
always 0 in the absence of _CBA as per the following:
- This is where we set addr (i.e. root->mcfg_addr) that will be passed to setup_mcfg_map()
and from it down to pci_mmconfig_insert():
372 static int acpi_pci_root_add(struct acpi_device *device,
373 const struct acpi_device_id *not_used)
374 {
...
432 root->mcfg_addr = acpi_pci_root_get_mcfg_addr(handle);
We eventually call into pci_acpi_scan_root():
521 root->bus = pci_acpi_scan_root(root);
acpi_pci_root_get_mcfg_addr() itself reads:
110 phys_addr_t acpi_pci_root_get_mcfg_addr(acpi_handle handle)
111 {
112 acpi_status status = AE_NOT_EXIST;
113 unsigned long long mcfg_addr;
114
115 if (handle)
116 status = acpi_evaluate_integer(handle, METHOD_NAME__CBA,
117 NULL, &mcfg_addr);
118 if (ACPI_FAILURE(status))
119 return 0;
120
121 return (phys_addr_t)mcfg_addr;
122 }
which means that it will return 0 if no _CBA.
FWIW, the above was introduced by commit:
f4b57a3 PCI/ACPI: provide MMCONFIG address for PCI host bridges
which is fine AFAICT given that it doesn't change the outcome of the non _CBA
case..
So the question is should commit
07f9b61 x86/PCI: MMCONFIG: Check earlier for MMCONFIG region at address zero
be reverted? or am I missing something?
Cheers,
Hedi.
--
Be careful of reading health books, you might die of a misprint.
-- Mark Twain
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