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Re: [RFC PATCH 00/13] Support UXL field in mstatus

From: LIU Zhiwei
Subject: Re: [RFC PATCH 00/13] Support UXL field in mstatus
Date: Mon, 9 Aug 2021 09:25:42 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0

On 2021/8/6 下午6:05, Alistair Francis wrote:
On Thu, Aug 5, 2021 at 5:15 PM LIU Zhiwei <zhiwei_liu@c-sky.com> wrote:

On 2021/8/5 下午2:01, Alistair Francis wrote:
On Thu, Aug 5, 2021 at 12:55 PM LIU Zhiwei <zhiwei_liu@c-sky.com> wrote:
This patch set implements UXL field in mstatus register. Programmer can change
UXLEN by writting to this field. So that you can run a 32 bit program
on a 64 bit CPU.
Awesome! Do you have any steps for building a rootFS to test this?
Not yet.  It depends on Linux support which  will not start until
October.  Maybe as a rough test,
we can run the 32 glibc test cases on qemu-riscv64 with an option
uxl32=true(not implement yet).
Hmmm... That's a pain. We really need some way to test this (and
ensure no future breakages occur). But I see the problem of no
software support until this exists.

It sounds like you or a colleague is planning on adding Linux support.
Maybe we will have to wait until that at least exists before this can
go upstream. We could at least review this before hand though

Enough for me. Thanks. I will also think more about Richard's advice, maybe we can merge 32bit cpu and UXL32 into one in the future.


, so
thanks for sending the series.

A 32-bit glibc test on qemu-riscv64 would probably also be enough, at
least as a start.




This patch set depends on one patch set by Richard Henderson

LIU Zhiwei (13):
    target/riscv: Add UXL to tb flags
    target/riscv: Support UXL32 for branch instructions
    target/riscv: Support UXL32 on 64-bit cpu for load/store
    target/riscv: Support UXL32 for slit/sltiu
    target/riscv: Support UXL32 for shift instruction
    target/riscv: Fix div instructions
    target/riscv: Support UXL32 for RVM
    target/riscv: Support UXL32 for vector instructions
    target/riscv: Support UXL32 for atomic instructions
    target/riscv: Support UXL32 for float instructions
    target/riscv: Fix srow
    target/riscv: Support UXL32 for RVB
    target/riscv: Changing the width of U-mode CSR

   target/riscv/cpu.h                      |  18 +++
   target/riscv/csr.c                      |  42 +++++-
   target/riscv/insn_trans/trans_rva.c.inc |  36 ++++-
   target/riscv/insn_trans/trans_rvb.c.inc |  51 +++++--
   target/riscv/insn_trans/trans_rvd.c.inc |   4 +-
   target/riscv/insn_trans/trans_rvf.c.inc |   4 +-
   target/riscv/insn_trans/trans_rvi.c.inc |  62 ++++++--
   target/riscv/insn_trans/trans_rvm.c.inc |  24 ++-
   target/riscv/insn_trans/trans_rvv.c.inc |  44 +++---
   target/riscv/translate.c                | 186 ++++++++++++++++++++----
   target/riscv/vector_helper.c            |  54 +++++--
   11 files changed, 414 insertions(+), 111 deletions(-)


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