powerpc/iommu: Do not immediately panic when failed IOMMU table allocation

Most platforms allocate IOMMU table structures (specifically it_map)
at the boot time and when this fails - it is a valid reason for panic().

However the powernv platform allocates it_map after a device is returned
to the host OS after being passed through and this happens long after
the host OS booted. It is quite possible to trigger the it_map allocation
panic() and kill the host even though it is not necessary - the host OS
can still use the DMA bypass mode (requires a tiny fraction of it_map's
memory) and even if that fails, the host OS is runnnable as it was without
the device for which allocating it_map causes the panic.

Instead of immediately crashing in a powernv/ioda2 system, this prints
an error and continues. All other platforms still call panic().

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Leonardo Bras <leobras.c@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210216033307.69863-3-aik@ozlabs.ru

1 files changed, 8 insertions, 7 deletions

diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
index f0f901683a2f..66c3c3337334 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -1762,7 +1762,8 @@ found:
 	tbl->it_ops = &pnv_ioda1_iommu_ops;
 	pe->table_group.tce32_start = tbl->it_offset << tbl->it_page_shift;
 	pe->table_group.tce32_size = tbl->it_size << tbl->it_page_shift;
-	iommu_init_table(tbl, phb->hose->node, 0, 0);
+	if (!iommu_init_table(tbl, phb->hose->node, 0, 0))
+		panic("Failed to initialize iommu table");
 
 	pe->dma_setup_done = true;
 	return;
@@ -1930,16 +1931,16 @@ static long pnv_pci_ioda2_setup_default_config(struct pnv_ioda_pe *pe)
 		res_start = pe->phb->ioda.m32_pci_base >> tbl->it_page_shift;
 		res_end = min(window_size, SZ_4G) >> tbl->it_page_shift;
 	}
-	iommu_init_table(tbl, pe->phb->hose->node, res_start, res_end);
 
-	rc = pnv_pci_ioda2_set_window(&pe->table_group, 0, tbl);
+	if (iommu_init_table(tbl, pe->phb->hose->node, res_start, res_end))
+		rc = pnv_pci_ioda2_set_window(&pe->table_group, 0, tbl);
+	else
+		rc = -ENOMEM;
 	if (rc) {
-		pe_err(pe, "Failed to configure 32-bit TCE table, err %ld\n",
-				rc);
+		pe_err(pe, "Failed to configure 32-bit TCE table, err %ld\n", rc);
 		iommu_tce_table_put(tbl);
-		return rc;
+		tbl = NULL; /* This clears iommu_table_base below */
 	}
-
 	if (!pnv_iommu_bypass_disabled)
 		pnv_pci_ioda2_set_bypass(pe, true);