Date: Fri, 14 Dec 2018 18:40:09 +0000 (UTC) From: Mark Johnston <markj@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org Subject: svn commit: r342092 - stable/12/sys/riscv/include Message-ID: <201812141840.wBEIe94p023523@repo.freebsd.org>
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Author: markj Date: Fri Dec 14 18:40:08 2018 New Revision: 342092 URL: https://svnweb.freebsd.org/changeset/base/342092 Log: MFC r341694: Update the description of the address space layout on RISC-V. Modified: stable/12/sys/riscv/include/vmparam.h Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/riscv/include/vmparam.h ============================================================================== --- stable/12/sys/riscv/include/vmparam.h Fri Dec 14 18:39:17 2018 (r342091) +++ stable/12/sys/riscv/include/vmparam.h Fri Dec 14 18:40:08 2018 (r342092) @@ -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)
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