[PATCH 4.2 055/134] powerpc/powernv/pci-ioda: fix 32-bit TCE table init in kdump kernel

Greg Kroah-Hartman
2015-09-26T20:58:54Z

From: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>

commit bb0054552d080dd929907c5925d4bedc8bf6def7 upstream.

When attempting to kdump with the 4.2 kernel, we see for each PCI
device:

pci 0003:01 : [PE# 000] Assign DMA32 space
pci 0003:01 : [PE# 000] Setting up 32-bit TCE table at 0..80000000
pci 0003:01 : [PE# 000] Failed to create 32-bit TCE table, err -22
PCI: Domain 0004 has 8 available 32-bit DMA segments
PCI: 4 PE# for a total weight of 70
pci 0004:01 : [PE# 002] Assign DMA32 space
pci 0004:01 : [PE# 002] Setting up 32-bit TCE table at 0..80000000
pci 0004:01 : [PE# 002] Failed to create 32-bit TCE table, err -22
pci 0004:0d : [PE# 005] Assign DMA32 space
pci 0004:0d : [PE# 005] Setting up 32-bit TCE table at 0..80000000
pci 0004:0d : [PE# 005] Failed to create 32-bit TCE table, err -22
pci 0004:0e : [PE# 006] Assign DMA32 space
pci 0004:0e : [PE# 006] Setting up 32-bit TCE table at 0..80000000
pci 0004:0e : [PE# 006] Failed to create 32-bit TCE table, err -22
pci 0004:10 : [PE# 008] Assign DMA32 space
pci 0004:10 : [PE# 008] Setting up 32-bit TCE table at 0..80000000
pci 0004:10 : [PE# 008] Failed to create 32-bit TCE table, err -22

and eventually the kdump kernel fails to boot as none of the PCI devices
(including the disk controller) are successfully initialized.

The EINVAL response is because the DMA window (the 2GB base window) is
larger than the kdump kernel's reserved memory (crashkernel=, in this
case specified to be 1024M). The check in question,

if ((window_size > memory_hotplug_max()) || !is_power_of_2(window_size))

is a valid sanity check for pnv_pci_ioda2_table_alloc_pages(), so adjust
the caller to pass in a smaller window size if our maximum memory value
is smaller than the DMA window.

After this change, the PCI devices successfully set up the 32-bit TCE
table and kdump succeeds.

The problem was seen on a Firestone machine originally.

Fixes: aca6913f5551 ("powerpc/powernv/ioda2: Introduce helpers to allocate TCE pages")
Signed-off-by: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
[mpe: Coding style pedantry, use u64, change the indentation]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/powerpc/platforms/powernv/pci-ioda.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)

--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -2078,9 +2078,17 @@ static long pnv_pci_ioda2_setup_default_
struct iommu_table *tbl = NULL;
long rc;

+ /*
+ * In memory constrained environments, e.g. kdump kernel, the
+ * DMA window can be larger than available memory, which will
+ * cause errors later.
+ */
+ const u64 window_size = min((u64)pe->table_group.tce32_size,
+ memory_hotplug_max());
+
rc = pnv_pci_ioda2_create_table(&pe->table_group, 0,
IOMMU_PAGE_SHIFT_4K,
- pe->table_group.tce32_size,
+ window_size,
POWERNV_IOMMU_DEFAULT_LEVELS, &tbl);
if (rc) {
pe_err(pe, "Failed to create 32-bit TCE table, err %ld",