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Try to allocate within constraint area first. In case the area is exhausted, try allocation at other memory locations. The motivation for this is to limit DMA allocations to 4GB (since some devices require addresses below 4GB). On some platforms there is little physical RAM in this area (<1GB) and the constrainted area exhausts. In case an IOMMU is present, RAM at higher locations can still be mapped below 4GB, which is done in the platform drivers. issue #4665
This is generic part of the Genode implementation. It consists of two parts: :_Core_: is the ultimate root of the Genode application tree and provides abstractions for the lowest-level hardware resources such as RAM, ROM, CPU, and generic device access. All generic parts of Core can be found here - for system-specific implementations refer to the appropriate 'base-<system>' directory. :_Base libraries and protocols_: that are used by each Genode component to interact with other components. This is the glue that holds everything together. _Core_ may export information about the hardware platform by an ROM called 'platform_info'. Depending on the platform, e.g. ARM or x86 or riscv, and depending on the boot mode and boot loader and kernel, some nodes may not be populated. !<platform_info> ! <acpi revision="2" rsdt="0x1fe93074" xsdt="0x1fe930e8"/> ! <boot> ! <framebuffer phys="0x7300000" width="1024" height="768" bpp="32"/> ! </boot> !</platform_info> If the ACPI RSDT and XSDT physical pointer is reported by the used kernel and/or bootloader, _Core_ may provide this information by the ROM. If the graphic device is initialised and can be directly used by a framebuffer driver, _Core_ may provide the physical pointer to the framebuffer, the resolution and color depth in bits.