From 0169cffd9364d2c70d556cc8ad3c083c79c8aeb1 Mon Sep 17 00:00:00 2001 From: Yunsup Lee Date: Wed, 6 Aug 2014 17:13:47 -0700 Subject: [PATCH] update readme --- README.md | 157 +++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 156 insertions(+), 1 deletion(-) diff --git a/README.md b/README.md index 3d32d19..9a4e913 100644 --- a/README.md +++ b/README.md @@ -4,7 +4,7 @@ riscv-tests About ----------- -Unit tests for RISC-V processors +This repository hosts unit tests for RISC-V processors. Building from repository ----------------------------- @@ -20,3 +20,158 @@ install path, and that the riscv-gcc package is installed. $ make $ make install +The rest of this document describes the format of test programs for the RISC-V +architecture. + +Test Virtual Machines +------------------------- + +To allow maximum reuse of a given test, each test program is constrained to +only use features of a given *test virtual machine* or TVM. A TVM hides +differences between alternative implementations by defining: + +* The set of registers and instructions that can be used. +* Which portions of memory can be accessed. +* The way the test program starts and ends execution. +* The way that test data is input. +* The way that test results are output. + +The following table shows the TVMs currently defined for RISC-V. All of these +TVMs only support a single hardware thread. + +TVM Name | Description +--- | --- +`rv32ui` | RV32 user-level, integer only +`rv32si` | RV32 supervisor-level, integer only +`rv64ui` | RV64 user-level, integer only +`rv64uf` | RV64 user-level, integer and floating-point +`rv64uv` | RV64 user-level, integer, floating-point, and vector +`rv64si` | RV64 supervisor-level, integer only +`rv64sv` | RV64 supervisor-level, integer and vector + +A test program for RISC-V is written within a single assembly language file, +which is passed through the C preprocessor, and all regular assembly +directives can be used. An example test program is shown below. Each test +program should first include the `riscv test.h` header file, which defines the +macros used by the TVM. The header file will have different contents depending +on the target environment for which the test will be built. One of the goals +of the various TVMs is to allow the same test program to be compiled and run +on very different target environments yet still produce the same results. The +following table shows the target environment currently defined. + +Target Environment Name | Description +--- | --- +`p` | virtual memory is disabled, only core 0 boots up +`pm` | virtual memory is disabled, all cores boot up +`pt` | virtual memory is disabled, timer interrupt fires every 100 cycles +`v` | virtual memory is enabled + +Each test program must next specify for which TVM it is designed by including +the appropriate TVM macro, `RVTEST_RV64U` in this example. This specification +can change the way in which subsequent macros are interpreted, and supports +a static check of the TVM functionality used by the program. + +The test program will begin execution at the first instruction after +`RVTEST_CODE_BEGIN`, and continue until execution reaches an `RVTEST_PASS` +macro or the `RVTEST_CODE_END` macro, which is implicitly a success. A test +can explicitly fail by invoking the `RVTEST_FAIL` macro. + +The example program contains self-checking code to test the result of the add. +However, self-checks rely on correct functioning of the processor instructions +used to implement the self check (e.g., the branch) and so cannot be the only +testing strategy. + +All tests should also contain a test data section, delimited by +`RVTEST_DATA_BEGIN` and `RVTEST_DATA_END`. There is no alignment guarantee for +the start of the test data section, so regular assembler alignment +instructions should be used to ensure desired alignment of data values. This +region of memory will be captured at the end of the test to act as a signature +from the test. The signature can be compared with that from a run on the +golden model. + +Any given test environment for running tests should also include a timeout +facility, which will class a test as failing if it does not successfully +complete a test within a reasonable time bound. + + #include "riscv_test.h" + + RVTEST_RV64U # Define TVM used by program. + + # Test code region. + RVTEST_CODE_BEGIN # Start of test code. + lw x2, testdata + addi x2, 1 # Should be 42 into $2. + sw x2, result # Store result into memory overwriting 1s. + li x3, 42 # Desired result. + bne x2, x3, fail # Fail out if doesn't match. + RVTEST_PASS # Signal success. + fail: + RVTEST_FAIL + RVTEST_CODE_END # End of test code. + + # Input data section. + # This section is optional, and this data is NOT saved in the output. + .data + .align 3 + testdata: + .dword 41 + + # Output data section. + RVTEST_DATA_BEGIN # Start of test output data region. + .align 3 + result: + .dword -1 + RVTEST_DATA_END # End of test output data region. + +User-Level TVMs +-------------------- + +Test programs for the `rv32u*` and `rv64u*` TVMs can contain all instructions +from the respective base user-level ISA (RV32 or RV64), except for those with +the SYSTEM major opcode (syscall, break, rdcycle, rdtime, rdinstret). All user +registers (pc, x0-x31, f0-f31, fsr) can be accessed. + +The `rv32ui` and `rv64ui` TVMs are integer-only subsets of `rv32u` and `rv64u` +respectively. These subsets can not use any floating-point instructions (major +opcodes: LOAD-FP, STORE-FP, MADD, MSUB, NMSUB, NMADD, OP-FP), and hence cannot +access the floating-point register state (f0รข-f31 and fsr). The integer-only +TVMs are useful for initial processor bringup and to test simpler +implementations that lack a hardware FPU. + +Note that any `rv32ui` test program is also valid for the `rv32u` TVM, and +similarly `rv64ui` is a strict subset of `rv64u`. To allow a given test to run +on the widest possible set of implementations, it is desirable to write any +given test to run on the smallest or least capable TVM possible. For example, +any simple tests of integer functionality should be written for the `rv64ui` +TVM, as the same test can then be run on RV64 implementations with or without a +hardware FPU. As another example, all tests for these base user-level TVMs will +also be valid for more advanced processors with instruction-set extensions. + +At the start of execution, the values of all registers are undefined. All +branch and jump destinations must be to labels within the test code region of +the assembler source file. The code and data sections will be relocated +differently for the various implementations of the test environment, and so +test program results shall not depend on absolute addresses of instructions or +data memory. The test build environment should support randomization of the +section relocation to provide better coverage and to ensure test signatures do +not contain absolute addresses. + +Supervisor-Level TVMs +-------------------------- + +The supervisor-level TVMs allow testing of supervisor-level state and +instructions. As with the user-level TVMs, we provide integer-only +supervisor-level TVMs indicated with a trailing `i`. + +History and Acknowledgements +--------------------------------- + +This style of test virtual machine originated with the T0 (Torrent-0) vector +microprocessor project at UC Berkeley and ICSI, begun in 1992. The main +developers of this test strategy were Krste Asanovic and David Johnson. A +precursor to `torture` was `rantor` developed by Phil Kohn at ICSI. + +A variant of this testing approach was also used for the Scale vector-thread +processor at MIT, begun in 2000. Ronny Krashinsky and Christopher Batten were +the principal architects of the Scale chip. Jeffrey Cohen and Mark Hampton +developed a version of torture capable of generating vector-thread code. -- 2.30.2