From c8b6dbddbb0d8eac76617c9935df816562326a5e Mon Sep 17 00:00:00 2001 From: DrChat Date: Fri, 21 Oct 2016 13:04:10 -0500 Subject: [PATCH] Add some documentation about the guest memory --- docs/cpu.md | 54 +++++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 48 insertions(+), 6 deletions(-) diff --git a/docs/cpu.md b/docs/cpu.md index a03deeade..04903647f 100644 --- a/docs/cpu.md +++ b/docs/cpu.md @@ -1,5 +1,47 @@ # CPU Documentation +## Code + +Xenia uses a dynamic recompiler to recompile PPC instructions to host +architecture instructions at runtime. Functions are converted as they +are called by the guest/host and stored in a code cache. Currently, the +only backend that exists is the x64 backend. + +Unfortunately, one problem with this approach is that code usually never +ends up in the same spot across reruns due to multithreading. Host code +may also morph depending on which spots of a function are called first. + +## Memory + +Xenia defines virtual memory as a mapped range beginning at Memory::virtual_membase(), +and physical memory as another mapped range from Memory::physical_membase() +(usually 0x100000000 and 0x200000000, respectively). If the default bases are +not available, they are shifted left 1 bit until an available range is found. + +The guest only has access to these ranges, nothing else. + +### Map +``` +0x00000000 - 0x3FFFFFFF (1024mb) - virtual 4k pages +0x40000000 - 0x7FFFFFFF (1024mb) - virtual 64k pages +0x80000000 - 0x8BFFFFFF ( 192mb) - xex 64k pages +0x8C000000 - 0x8FFFFFFF ( 64mb) - xex 64k pages (encrypted) +0x90000000 - 0x9FFFFFFF ( 256mb) - xex 4k pages +0xA0000000 - 0xBFFFFFFF ( 512mb) - physical 64k pages (overlapped) +0xC0000000 - 0xDFFFFFFF - physical 16mb pages (overlapped) +0xE0000000 - 0xFFFFFFFF - physical 4k pages (overlapped) +``` + +Virtual pages are usually allocated by NtAllocateVirtualMemory, and +physical pages are usually allocated by MmAllocatePhysicalMemoryEx. + +Virtual pages mapped to physical memory are also mapped to the physical membase, +i.e. virtual 0xA0000000 == physical 0x00000000 + +Unfortunately, the 0xE0000000-0xFFFFFFFF range is unused in Xenia because +it maps to physical memory with a single page offset, which is impossible +to do under the Win32 API. + ## Memory Management TODO @@ -8,12 +50,12 @@ TODO ### PowerPC -The processor in the 360 is a 64-bit PowerPC chip running with 32-bit memory -addresses. This can make some of the documentation a little confusing as most -of the PowerPC docs only have a 'you're in 32 or 64' style. The CPU is largely -similar to the PPC part in the PS3, so Cell documents often line up for the -core instructions. The 360 adds some additional AltiVec instructions, though, -which are only documented in a few places (like the gcc source code, etc). +The processor in the 360 is a 64-bit PowerPC chip running in 32-bit mode. +Programs are still allowed to use 64-bit PowerPC instructions, and registers +are 64-bit as well, but 32-bit instructions will run in 32-bit mode. +The CPU is largely similar to the PPC part in the PS3, so Cell documents +often line up for the core instructions. The 360 adds some additional AltiVec +instructions, though,which are only documented in a few places (like the gcc source code, etc). * [Free60 Info](http://www.free60.org/Xenon_\(CPU\)) * [Power ISA docs](https://www.power.org/wp-content/uploads/2012/07/PowerISA_V2.06B_V2_PUBLIC.pdf) (aka 'PowerISA')