[PATCH v2] resource: limit request_free_mem_region based on arch_get_mappable_range

[D Scott Phillips]

On arm64 prior to commit 32697ff38287 ("arm64: vmemmap: Avoid base2 order
of struct page size to dimension region"), the amdgpu driver could trip
over the warning of:

`WARN_ON((start < VMEMMAP_START) || (end > VMEMMAP_END));`

in vmemmap_populate()[1]. After that commit, it becomes a translation fault
and panic[2].

The cause is that the amdgpu driver allocates some unused space from
iomem_resource and claims it as MEMORY_DEVICE_PRIVATE and
devm_memremap_pages() it. An address above those backed by the arm64
vmemmap is picked.

Limit request_free_mem_region() so that only addresses within the
arch_get_mappable_range() can be chosen as device private addresses.

[1]: Call trace:
      vmemmap_populate+0x30/0x48
      __populate_section_memmap+0x40/0x90
      sparse_add_section+0xfc/0x3e8
      __add_pages+0xb4/0x168
      pagemap_range+0x300/0x410
      memremap_pages+0x184/0x2d8
      devm_memremap_pages+0x30/0x90
      kgd2kfd_init_zone_device+0xe0/0x1f0 [amdgpu]
      amdgpu_device_ip_init+0x674/0x888 [amdgpu]
      amdgpu_device_init+0x7bc/0xed8 [amdgpu]
      amdgpu_driver_load_kms+0x28/0x1c0 [amdgpu]
      amdgpu_pci_probe+0x194/0x580 [amdgpu]
      local_pci_probe+0x48/0xb8
      work_for_cpu_fn+0x24/0x40
      process_one_work+0x170/0x3e0
      worker_thread+0x2ac/0x3e0
      kthread+0xf4/0x108
      ret_from_fork+0x10/0x20

[2]: Unable to handle kernel paging request at virtual address
             000001ffa6000034
     Mem abort info:
       ESR = 0x0000000096000044
       EC = 0x25: DABT (current EL), IL = 32 bits
       SET = 0, FnV = 0
       EA = 0, S1PTW = 0
       FSC = 0x04: level 0 translation fault
     Data abort info:
       ISV = 0, ISS = 0x00000044, ISS2 = 0x00000000
       CM = 0, WnR = 1, TnD = 0, TagAccess = 0
       GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
     user pgtable: 4k pages, 48-bit VAs, pgdp=000008000287c000
     [000001ffa6000034] pgd=0000000000000000, p4d=0000000000000000
     Call trace:
      __init_zone_device_page.constprop.0+0x2c/0xa8
      memmap_init_zone_device+0xf0/0x210
      pagemap_range+0x1e0/0x410
      memremap_pages+0x18c/0x2e0
      devm_memremap_pages+0x30/0x90
      kgd2kfd_init_zone_device+0xf0/0x200 [amdgpu]
      amdgpu_device_ip_init+0x674/0x888 [amdgpu]
      amdgpu_device_init+0x7a4/0xea0 [amdgpu]
      amdgpu_driver_load_kms+0x28/0x1c0 [amdgpu]
      amdgpu_pci_probe+0x1a0/0x560 [amdgpu]
      local_pci_probe+0x48/0xb8
      work_for_cpu_fn+0x24/0x40
      process_one_work+0x170/0x3e0
      worker_thread+0x2ac/0x3e0
      kthread+0xf4/0x108
      ret_from_fork+0x10/0x20

Signed-off-by: D Scott Phillips <scott at os.amperecomputing.com>
---
Link to v1: https://lore.kernel.org/all/20240703210707.1986816-1-scott@os.amperecomputing.com/
Changes since v1:
 - Change from fiddling the architecture's MAX_PHYSMEM_BITS to checking
   arch_get_mappable_range().

 kernel/resource.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index fcbca39dbc450..6f256aa0191b4 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1832,25 +1832,28 @@ static resource_size_t gfr_start(struct resource *base, resource_size_t size,
 	if (flags & GFR_DESCENDING) {
 		resource_size_t end;
 
-		end = min_t(resource_size_t, base->end,
+		end = min3(base->end, arch_get_mappable_range().end,
 			    (1ULL << MAX_PHYSMEM_BITS) - 1);
 		return end - size + 1;
 	}
 
-	return ALIGN(base->start, align);
+	return ALIGN(max_t(resource_size_t, base->start,
+			   arch_get_mappable_range().start), align);
 }
 
 static bool gfr_continue(struct resource *base, resource_size_t addr,
 			 resource_size_t size, unsigned long flags)
 {
+
 	if (flags & GFR_DESCENDING)
-		return addr > size && addr >= base->start;
+		return addr > size && addr >= base->start &&
+		       addr >= arch_get_mappable_range().start;
 	/*
 	 * In the ascend case be careful that the last increment by
 	 * @size did not wrap 0.
 	 */
 	return addr > addr - size &&
-	       addr <= min_t(resource_size_t, base->end,
+	       addr <= min3(base->end, arch_get_mappable_range().end,
 			     (1ULL << MAX_PHYSMEM_BITS) - 1);
 }
 
-- 
2.45.2