5.15-stable patches

added patches:
	x86-mm-init-handle-the-special-case-of-device-private-pages-in-add_pages-to-not-increase-max_pfn-and-trigger-dma_addressing_limited-bounce-buffers.patch

diff --git a/queue-5.15/series b/queue-5.15/series
index 41cfa3144556ee162043febff143a692a060a7fa..72375e32cc4da3d18aae90bdc96dfb9e0d09da83 100644 (file)
--- a/queue-5.15/series
+++ b/queue-5.15/series
@@ -1,3 +1,4 @@
+x86-mm-init-handle-the-special-case-of-device-private-pages-in-add_pages-to-not-increase-max_pfn-and-trigger-dma_addressing_limited-bounce-buffers.patch
 scsi-target-iscsi-fix-timeout-on-deleted-connection.patch
 virtio_ring-fix-data-race-by-tagging-event_triggered.patch
 dma-mapping-avoid-potential-unused-data-compilation-.patch

diff --git a/queue-5.15/x86-mm-init-handle-the-special-case-of-device-private-pages-in-add_pages-to-not-increase-max_pfn-and-trigger-dma_addressing_limited-bounce-buffers.patch b/queue-5.15/x86-mm-init-handle-the-special-case-of-device-private-pages-in-add_pages-to-not-increase-max_pfn-and-trigger-dma_addressing_limited-bounce-buffers.patch
new file mode 100644 (file)
index 0000000..937e7eb
--- /dev/null
+++ b/queue-5.15/x86-mm-init-handle-the-special-case-of-device-private-pages-in-add_pages-to-not-increase-max_pfn-and-trigger-dma_addressing_limited-bounce-buffers.patch
@@ -0,0 +1,106 @@
+From 7170130e4c72ce0caa0cb42a1627c635cc262821 Mon Sep 17 00:00:00 2001
+From: Balbir Singh <balbirs@nvidia.com>
+Date: Tue, 1 Apr 2025 11:07:52 +1100
+Subject: x86/mm/init: Handle the special case of device private pages in add_pages(), to not increase max_pfn and trigger dma_addressing_limited() bounce buffers
+ bounce buffers
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+From: Balbir Singh <balbirs@nvidia.com>
+
+commit 7170130e4c72ce0caa0cb42a1627c635cc262821 upstream.
+
+As Bert Karwatzki reported, the following recent commit causes a
+performance regression on AMD iGPU and dGPU systems:
+
+  7ffb791423c7 ("x86/kaslr: Reduce KASLR entropy on most x86 systems")
+
+It exposed a bug with nokaslr and zone device interaction.
+
+The root cause of the bug is that, the GPU driver registers a zone
+device private memory region. When KASLR is disabled or the above commit
+is applied, the direct_map_physmem_end is set to much higher than 10 TiB
+typically to the 64TiB address. When zone device private memory is added
+to the system via add_pages(), it bumps up the max_pfn to the same
+value. This causes dma_addressing_limited() to return true, since the
+device cannot address memory all the way up to max_pfn.
+
+This caused a regression for games played on the iGPU, as it resulted in
+the DMA32 zone being used for GPU allocations.
+
+Fix this by not bumping up max_pfn on x86 systems, when pgmap is passed
+into add_pages(). The presence of pgmap is used to determine if device
+private memory is being added via add_pages().
+
+More details:
+
+devm_request_mem_region() and request_free_mem_region() request for
+device private memory. iomem_resource is passed as the base resource
+with start and end parameters. iomem_resource's end depends on several
+factors, including the platform and virtualization. On x86 for example
+on bare metal, this value is set to boot_cpu_data.x86_phys_bits.
+boot_cpu_data.x86_phys_bits can change depending on support for MKTME.
+By default it is set to the same as log2(direct_map_physmem_end) which
+is 46 to 52 bits depending on the number of levels in the page table.
+The allocation routines used iomem_resource's end and
+direct_map_physmem_end to figure out where to allocate the region.
+
+[ arch/powerpc is also impacted by this problem, but this patch does not fix
+  the issue for PowerPC. ]
+
+Testing:
+
+ 1. Tested on a virtual machine with test_hmm for zone device inseration
+
+ 2. A previous version of this patch was tested by Bert, please see:
+    https://lore.kernel.org/lkml/d87680bab997fdc9fb4e638983132af235d9a03a.camel@web.de/
+
+[ mingo: Clarified the comments and the changelog. ]
+
+Reported-by: Bert Karwatzki <spasswolf@web.de>
+Tested-by: Bert Karwatzki <spasswolf@web.de>
+Fixes: 7ffb791423c7 ("x86/kaslr: Reduce KASLR entropy on most x86 systems")
+Signed-off-by: Balbir Singh <balbirs@nvidia.com>
+Signed-off-by: Ingo Molnar <mingo@kernel.org>
+Cc: Brian Gerst <brgerst@gmail.com>
+Cc: Juergen Gross <jgross@suse.com>
+Cc: H. Peter Anvin <hpa@zytor.com>
+Cc: Linus Torvalds <torvalds@linux-foundation.org>
+Cc: Andrew Morton <akpm@linux-foundation.org>
+Cc: Christoph Hellwig <hch@lst.de>
+Cc: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
+Cc: Alex Deucher <alexander.deucher@amd.com>
+Cc: Christian König <christian.koenig@amd.com>
+Cc: David Airlie <airlied@gmail.com>
+Cc: Simona Vetter <simona@ffwll.ch>
+Link: https://lore.kernel.org/r/20250401000752.249348-1-balbirs@nvidia.com
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ arch/x86/mm/init_64.c |   15 ++++++++++++---
+ 1 file changed, 12 insertions(+), 3 deletions(-)
+
+--- a/arch/x86/mm/init_64.c
++++ b/arch/x86/mm/init_64.c
+@@ -955,9 +955,18 @@ int add_pages(int nid, unsigned long sta
+       ret = __add_pages(nid, start_pfn, nr_pages, params);
+       WARN_ON_ONCE(ret);
+ 
+-      /* update max_pfn, max_low_pfn and high_memory */
+-      update_end_of_memory_vars(start_pfn << PAGE_SHIFT,
+-                                nr_pages << PAGE_SHIFT);
++      /*
++       * Special case: add_pages() is called by memremap_pages() for adding device
++       * private pages. Do not bump up max_pfn in the device private path,
++       * because max_pfn changes affect dma_addressing_limited().
++       *
++       * dma_addressing_limited() returning true when max_pfn is the device's
++       * addressable memory can force device drivers to use bounce buffers
++       * and impact their performance negatively:
++       */
++      if (!params->pgmap)
++              /* update max_pfn, max_low_pfn and high_memory */
++              update_end_of_memory_vars(start_pfn << PAGE_SHIFT, nr_pages << PAGE_SHIFT);
+ 
+       return ret;
+ }