mirror of
https://github.com/FEX-Emu/FEX.git
synced 2026-10-25 18:00:49 +01:00
Ryan Houdek
df2f1ad074
Only a partial fix for #1330, still needs preemption disabled to work. On x86-64 hosts the Linux kernel resides in the top bit of VA which isn't mapped in to userspace. This means that userspace will never receive pointers living with that top bit set unless you're running a 57bit VA host. This results in userspace pointers never needing to do the sign extending pointer canonicalization. But additionally some applications actually don't understand the pointer canonicalization. This results in bugs like: https://github.com/golang/go/issues/49405 Now if you're running on a 57bit VA host, this will end up behaving like FEX but it seems like no one in golang land has really messed with 57bit VA yet. In AArch64, when configured with a 48bit VA, the userspace gets the full 48bit VA space and on EL mode switch has the full address range change to the kernel's 48bit VA. This means that we will /very/ likely allocate pointers in the high 48bit space since Linux currently allocates top-down. So behave more like x86-64, hide the top 128TB of memory space from the guest before boot. Testing: Took the M1Max 15ms to 21ms allocate the top 128TB.
FEXCore - Fast x86 Core emulation library
This is the core emulation library that is used for the FEX emulator project. This project aims to provide a fast and functional x86-64 emulation library that can meet and surpass other x86-64 emulation libraries.
Goals
- Be as fast as possible, beating and exceeding current options for x86-64 emulation
- 25% - 50% lower performance than native code would be desired target
- Use an IR to efficiently translate x86-64 to our host architecture
- Support a tiered recompiler to allow for fast runtime performance
- Support offline compilation and offline tooling for inspection and performance analysis
- Support threaded emulation. Including emulating x86-64's strong memory model on weak memory model architectures
- Support a significant portion of the x86-64 instruction space.
- Including MMX, SSE, SSE2, SSE3, SSSE3, and SSE4*
- Support fallback routines for uncommonly used x86-64 instructions
- Including x87 and 3DNow!
- Only support userspace emulation.
- All x86-64 instructions run as if they are under CPL-3(userland) security layer
- Minimal Linux Syscall emulation for testing purposes
- Portable library implementation in order to support easy integration in to applications
Target Host Architecture
The target host architecture for this library is AArch64. Specifically the ARMv8.1 version or newer. The CPU IR is designed with AArch64 in mind but there is a desire to run the recompiled code on other architectures as well. Multiple architecture support is desired for easier bringup and debugging, performance isn't as much of a priority there (ex. x86-64(guest) translated to x86-64(host))
Not currently goals but will be in the future
- 32bit x86 support
- This will be a desire in the future, but to lower the amount of work required, decided to push this off for now.
- Integration in to WINE
- Later generation of x86-64 instruction sets
- Including AVX, F16C, XOP, FMA, AVX2, etc
Not desired
- Kernel space emulation
- CPL0-2 emulation
- Real Mode, Protected Mode, Virtual-8086 Mode, System Management Mode
- IRQs
- SVM
- "Cycle Accurate" emulation
Dependencies
- clang-tidy if you want to ensure the code stays tidy
- cmake
- A C++17 compliant compiler (There are assumptions made about using Clang and LTO)