From: Alexey Kardashevskiy aik@ozlabs.ru
[ Upstream commit ad3976025b311cdeb822ad3e7a7554018cb0f83f ]
There is a possibility of having just one DMA window available with a limited capacity which the existing code does not handle that well. If the window is big enough for the system RAM but less than MAX_PHYSMEM_BITS (which we want when persistent memory is present), we create 1:1 window and leave persistent memory without DMA.
This disables 1:1 mapping entirely if there is persistent memory and either: - the huge DMA window does not cover the entire address space; - the default DMA window is removed.
This relies on reverted 54fc3c681ded ("powerpc/pseries/ddw: Extend upper limit for huge DMA window for persistent memory") to return the actual amount RAM in ddw_memory_hotplug_max() (posted separately).
Signed-off-by: Alexey Kardashevskiy aik@ozlabs.ru Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20211108040320.3857636-4-aik@ozlabs.ru Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/platforms/pseries/iommu.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c index ad96d6e13d1f6..8322ca86d5acf 100644 --- a/arch/powerpc/platforms/pseries/iommu.c +++ b/arch/powerpc/platforms/pseries/iommu.c @@ -1356,8 +1356,10 @@ static bool enable_ddw(struct pci_dev *dev, struct device_node *pdn) len = order_base_2(query.largest_available_block << page_shift); win_name = DMA64_PROPNAME; } else { - direct_mapping = true; - win_name = DIRECT64_PROPNAME; + direct_mapping = !default_win_removed || + (len == MAX_PHYSMEM_BITS) || + (!pmem_present && (len == max_ram_len)); + win_name = direct_mapping ? DIRECT64_PROPNAME : DMA64_PROPNAME; }
ret = create_ddw(dev, ddw_avail, &create, page_shift, len);