This is a note to let you know that I've just added the patch titled powerpc/pseries/ddw: Do not try direct mapping with persistent memory and one window to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: powerpc-pseries-ddw-do-not-try-direct-mapping-with-p.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 7aee3d2ccf3a363979c2845ddf05bf01ad4631e1 Author: Alexey Kardashevskiy <aik@xxxxxxxxx> Date: Mon Nov 8 15:03:19 2021 +1100 powerpc/pseries/ddw: Do not try direct mapping with persistent memory and one window [ 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@xxxxxxxxx> Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20211108040320.3857636-4-aik@xxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> 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);