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, 4 insertions, 2 deletions

diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index 91d0ba7559a6..42e195aaf23a 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -727,8 +727,10 @@ struct iommu_table *iommu_init_table(struct iommu_table *tbl, int nid,
 	sz = BITS_TO_LONGS(tbl->it_size) * sizeof(unsigned long);
 
 	tbl->it_map = vzalloc_node(sz, nid);
-	if (!tbl->it_map)
-		panic("iommu_init_table: Can't allocate %ld bytes\n", sz);
+	if (!tbl->it_map) {
+		pr_err("%s: Can't allocate %ld bytes\n", __func__, sz);
+		return NULL;
+	}
 
 	iommu_table_reserve_pages(tbl, res_start, res_end);