On Tue, Oct 08, 2024 at 03:06:22PM -0700, Oreoluwa Babatunde wrote: > The reserved_mem array is used to store data for the different > reserved memory regions defined in the DT of a device. The array > stores information such as region name, node reference, start-address, > and size of the different reserved memory regions. > > The array is currently statically allocated with a size of > MAX_RESERVED_REGIONS(64). This means that any system that specifies a > number of reserved memory regions greater than MAX_RESERVED_REGIONS(64) > will not have enough space to store the information for all the regions. > > This can be fixed by making the reserved_mem array a dynamically sized > array which is allocated using memblock_alloc() based on the exact > number of reserved memory regions defined in the DT. > > On architectures such as arm64, memblock allocated memory is not > writable until after the page tables have been setup. > This is an issue because the current implementation initializes the > reserved memory regions and stores their information in the array before > the page tables are setup. Hence, dynamically allocating the > reserved_mem array and attempting to write information to it at this > point will fail. > > Therefore, the allocation of the reserved_mem array will need to be done > after the page tables have been setup, which means that the reserved > memory regions will also need to wait until after the page tables have > been setup to be stored in the array. > > When processing the reserved memory regions defined in the DT, these > regions are marked as reserved by calling memblock_reserve(base, size). > Where: base = base address of the reserved region. > size = the size of the reserved memory region. > > Depending on if that region is defined using the "no-map" property, > memblock_mark_nomap(base, size) is also called. > > The "no-map" property is used to indicate to the operating system that a > mapping of the specified region must NOT be created. This also means > that no access (including speculative accesses) is allowed on this > region of memory except when it is coming from the device driver that > this region of memory is being reserved for.[1] > > Therefore, it is important to call memblock_reserve() and > memblock_mark_nomap() on all the reserved memory regions before the > system sets up the page tables so that the system does not unknowingly > include any of the no-map reserved memory regions in the memory map. > > There are two ways to define how/where a reserved memory region is > placed in memory: > i) Statically-placed reserved memory regions > i.e. regions defined with a set start address and size using the > "reg" property in the DT. > ii) Dynamically-placed reserved memory regions. > i.e. regions defined by specifying a range of addresses where they can > be placed in memory using the "alloc_ranges" and "size" properties > in the DT. > > The dynamically-placed reserved memory regions get assigned a start > address only at runtime. And this needs to be done before the page > tables are setup so that memblock_reserve() and memblock_mark_nomap() > can be called on the allocated region as explained above. > Since the dynamically allocated reserved_mem array can only be > available after the page tables have been setup, the information for > the dynamically-placed reserved memory regions needs to be stored > somewhere temporarily until the reserved_mem array is available. > > Therefore, this series makes use of a temporary static array to store > the information of the dynamically-placed reserved memory regions until > the reserved_mem array is allocated. > Once the reserved_mem array is available, the information is copied over > from the temporary array into the reserved_mem array, and the memory for > the temporary array is freed back to the system. > > The information for the statically-placed reserved memory regions does > not need to be stored in a temporary array because their starting > address is already stored in the devicetree. > Once the reserved_mem array is allocated, the information for the > statically-placed reserved memory regions is added to the array. > > Note: > Because of the use of a temporary array to store the information of the > dynamically-placed reserved memory regions, there still exists a > limitation of 64 for this particular kind of reserved memory regions. > >From my observation, these regions are typically small in number and > hence I expect this to not be an issue for now. > > Patch Versions: > > v10: > - Rebase patchset on v6.12-rc2. > > v9: > - fix issue reported from v8: > https://lore.kernel.org/all/DU0PR04MB92999E9EEE959DBC3B1EAB6E80932@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ > In v8, the rmem struct being passed into __reserved_mem_init_node() > was not the same as what was being stored in the reserved_mem array. > As a result, information such as rmem->ops was not being stored in > the array for these regions. > Make changes to pass the same reserved_mem struct into > __reserved_mem_init_node() as what is being stored in the reserved_mem > array. > > v8: > https://lore.kernel.org/all/20240830162857.2821502-1-quic_obabatun@xxxxxxxxxxx/ > - Check the value of initial_boot_params in > fdt_scan_reserved_mem_reg_nodes() to avoid breakage on architectures > where this is not being used as was found to be the case for x86 in > the issues reported below: > https://lore.kernel.org/all/202408192157.8d8fe8a9-oliver.sang@xxxxxxxxx/ > https://lore.kernel.org/all/ZsN_p9l8Pw2_X3j3@xxxxxxxxxxxxxxxxxx/ > > v7: > https://lore.kernel.org/all/20240809184814.2703050-1-quic_obabatun@xxxxxxxxxxx/ > - Make changes to initialize the reserved memory regions earlier in > response to issue reported in v6: > https://lore.kernel.org/all/20240610213403.GA1697364@thelio-3990X/ > > - For the reserved regions to be setup properly, > fdt_init_reserved_mem_node() needs to be called on each of the regions > before the page tables are setup. Since the function requires a > refernece to the devicetree node of each region, we are not able to > use the unflattened_devicetree APIs since they are not available until > after the page tables have been setup. > Hence, revert the use of the unflatten_device APIs as a result of this > limitation which was discovered in v6: > https://lore.kernel.org/all/986361f4-f000-4129-8214-39f2fb4a90da@xxxxxxxxx/ > https://lore.kernel.org/all/DU0PR04MB9299C3EC247E1FE2C373440F80DE2@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ > > v6: > https://lore.kernel.org/all/20240528223650.619532-1-quic_obabatun@xxxxxxxxxxx/ > - Rebased patchset on top of v6.10-rc1. > - Addressed comments received in v5 such as: > 1. Switched to using relevant typed functions such as > of_property_read_u32(), of_property_present(), etc. > 2. Switched to using of_address_to_resource() to read the "reg" > property of nodes. > 3. Renamed functions using "of_*" naming scheme instead of "dt_*". > > v5: > https://lore.kernel.org/all/20240328211543.191876-1-quic_obabatun@xxxxxxxxxxx/ > - Rebased changes on top of v6.9-rc1. > - Addressed minor code comments from v4. > > v4: > https://lore.kernel.org/all/20240308191204.819487-2-quic_obabatun@xxxxxxxxxxx/ > - Move fdt_init_reserved_mem() back into the unflatten_device_tree() > function. > - Fix warnings found by Kernel test robot: > https://lore.kernel.org/all/202401281219.iIhqs1Si-lkp@xxxxxxxxx/ > https://lore.kernel.org/all/202401281304.tsu89Kcm-lkp@xxxxxxxxx/ > https://lore.kernel.org/all/202401291128.e7tdNh5x-lkp@xxxxxxxxx/ > > v3: > https://lore.kernel.org/all/20240126235425.12233-1-quic_obabatun@xxxxxxxxxxx/ > - Make use of __initdata to delete the temporary static array after > dynamically allocating memory for reserved_mem array using memblock. > - Move call to fdt_init_reserved_mem() out of the > unflatten_device_tree() function and into architecture specific setup > code. > - Breaking up the changes for the individual architectures into separate > patches. > > v2: > https://lore.kernel.org/all/20231204041339.9902-1-quic_obabatun@xxxxxxxxxxx/ > - Extend changes to all other relevant architectures by moving > fdt_init_reserved_mem() into the unflatten_device_tree() function. > - Add code to use unflatten devicetree APIs to process the reserved > memory regions. > > v1: > https://lore.kernel.org/all/20231019184825.9712-1-quic_obabatun@xxxxxxxxxxx/ > > References: > [1] https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/reserved-memory/reserved-memory.yaml#L79 > > Oreoluwa Babatunde (2): > of: reserved_mem: Restruture how the reserved memory regions are > processed > of: reserved_mem: Add code to dynamically allocate reserved_mem array > > drivers/of/fdt.c | 5 +- > drivers/of/of_private.h | 3 +- > drivers/of/of_reserved_mem.c | 227 +++++++++++++++++++++++++++-------- > 3 files changed, 179 insertions(+), 56 deletions(-) Applied, thanks. Rob
