From 54fc3c681ded9437e4548e2501dc1136b23cfa9a Mon Sep 17 00:00:00 2001
From: Alexey Kardashevskiy <aik@ozlabs.ru>
Date: Tue, 31 Mar 2020 12:23:38 +1100
Subject: [PATCH] powerpc/pseries/ddw: Extend upper limit for huge DMA window
for persistent memory
References: FATE#327775 bsc#1142685 ltc#179509
Patch-mainline: v5.7-rc1
Git-commit: 54fc3c681ded9437e4548e2501dc1136b23cfa9a
Unlike normal memory ("memory" compatible type in the FDT), the
persistent memory ("ibm,pmemory" in the FDT) can be mapped anywhere in
the guest physical space and it can be used for DMA.
In order to maintain 1:1 mapping via the huge DMA window, we need to
know the maximum physical address at the time of the window setup. So
far we've been looking at "memory" nodes but "ibm,pmemory" does not
have fixed addresses and the persistent memory may be mapped
afterwards.
Since the persistent memory is still backed with page structs, use
MAX_PHYSMEM_BITS as the upper limit.
This effectively disables huge DMA window in LPAR under pHyp if
persistent memory is present but this is the best we can do for the
moment.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Tested-by: Wen Xiong<wenxiong@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200331012338.23773-1-aik@ozlabs.ru
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
arch/powerpc/platforms/pseries/iommu.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index 2e0a8eab5588..6d47b4a3ce39 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -945,6 +945,15 @@ static phys_addr_t ddw_memory_hotplug_max(void)
phys_addr_t max_addr = memory_hotplug_max();
struct device_node *memory;
+ /*
+ * The "ibm,pmemory" can appear anywhere in the address space.
+ * Assuming it is still backed by page structs, set the upper limit
+ * for the huge DMA window as MAX_PHYSMEM_BITS.
+ */
+ if (of_find_node_by_type(NULL, "ibm,pmemory"))
+ return (sizeof(phys_addr_t) * 8 <= MAX_PHYSMEM_BITS) ?
+ (phys_addr_t) -1 : (1ULL << MAX_PHYSMEM_BITS);
+
for_each_node_by_type(memory, "memory") {
unsigned long start, size;
int n_mem_addr_cells, n_mem_size_cells, len;
--
2.23.0