Author: markj Date: Fri Dec 7 15:56:40 2018 New Revision: 341694 URL: https://svnweb.freebsd.org/changeset/base/341694
Log: Update the description of the address space layout on RISC-V. This adds more detail and fixes some inaccuracies. Reviewed by: jhb MFC after: 1 week Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D18463 Modified: head/sys/riscv/include/vmparam.h Modified: head/sys/riscv/include/vmparam.h ============================================================================== --- head/sys/riscv/include/vmparam.h Fri Dec 7 15:55:23 2018 (r341693) +++ head/sys/riscv/include/vmparam.h Fri Dec 7 15:56:40 2018 (r341694) @@ -115,23 +115,24 @@ /** * Address space layout. * - * RISC-V implements up to a 48 bit virtual address space. The address space is - * split into 2 regions at each end of the 64 bit address space, with an - * out of range "hole" in the middle. + * RISC-V implements multiple paging modes with different virtual address space + * sizes: SV32, SV39 and SV48. SV39 permits a virtual address space size of + * 512GB and uses a three-level page table. Since this is large enough for most + * purposes, we currently use SV39 for both userland and the kernel, avoiding + * the extra translation step required by SV48. * - * We limit the size of the two spaces to 39 bits each. + * The address space is split into two regions at each end of the 64-bit address + * space: * - * Upper region: 0xffffffffffffffff - * 0xffffff8000000000 + * 0x0000000000000000 - 0x0000003fffffffff 256GB user map + * 0x0000004000000000 - 0xffffffbfffffffff unmappable + * 0xffffffc000000000 - 0xffffffc7ffffffff 32GB kernel map + * 0xffffffc800000000 - 0xffffffcfffffffff 32GB unused + * 0xffffffd000000000 - 0xffffffefffffffff 128GB direct map + * 0xfffffff000000000 - 0xffffffffffffffff 64GB unused * - * Hole: 0xffffff7fffffffff - * 0x0000008000000000 + * The kernel is loaded at the beginning of the kernel map. * - * Lower region: 0x0000007fffffffff - * 0x0000000000000000 - * - * We use the upper region for the kernel, and the lower region for userland. - * * We define some interesting address constants: * * VM_MIN_ADDRESS and VM_MAX_ADDRESS define the start and end of the entire @@ -146,11 +147,9 @@ #define VM_MIN_ADDRESS (0x0000000000000000UL) #define VM_MAX_ADDRESS (0xffffffffffffffffUL) -/* 32 GiB of kernel addresses */ #define VM_MIN_KERNEL_ADDRESS (0xffffffc000000000UL) #define VM_MAX_KERNEL_ADDRESS (0xffffffc800000000UL) -/* 128 GiB maximum for the direct map region */ #define DMAP_MIN_ADDRESS (0xffffffd000000000UL) #define DMAP_MAX_ADDRESS (0xfffffff000000000UL) _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
