feat[bsp][xuantie]: c908 support rt-smart;

[BadmintonMaster]

拉取/合并请求描述：(PR description)

[

为什么提交这份PR (why to submit this PR)

本PR代为提交，功能为：c908 support rt-smart
原始commit: shuta.lst/rt-thread@53d4922049

你的解决方案是什么 (what is your solution)

新增 bsp/xuantie/virt64/c908支持，并且支持rtt smart模式
SMP适配性修改libcpu/risc-v/common64/mmu.c

请提供验证的bsp和config (provide the config and bsp)

bsp\xuantie\virt64\c908
bsp\xuantie\virt64\c908.config

• BSP:
  bsp\xuantie\virt64\c908

• .config:
  bsp\xuantie\virt64\c908.config

• action:

]

当前拉取/合并请求的状态 Intent for your PR

必须选择一项 Choose one (Mandatory):

• 本拉取/合并请求是一个草稿版本 This PR is for a code-review and is intended to get feedback
• 本拉取/合并请求是一个成熟版本 This PR is mature, and ready to be integrated into the repo

代码质量 Code Quality：

我在这个拉取/合并请求中已经考虑了 As part of this pull request, I've considered the following:

• 已经仔细查看过代码改动的对比 Already check the difference between PR and old code
• 代码风格正确，包括缩进空格，命名及其他风格 Style guide is adhered to, including spacing, naming and other styles
• 没有垃圾代码，代码尽量精简，不包含#if 0代码，不包含已经被注释了的代码 All redundant code is removed and cleaned up
• 所有变更均有原因及合理的，并且不会影响到其他软件组件代码或BSP All modifications are justified and not affect other components or BSP
• 对难懂代码均提供对应的注释 I've commented appropriately where code is tricky
• 代码是高质量的 Code in this PR is of high quality
• 已经使用clang-format 源码格式化工具确保格式符合RT-Thread代码规范 This PR has been formatted with clang-format and complies with RT-Thread code specification
• 如果是新增bsp, 已经添加ci检查到.github/ALL_BSP_COMPILE.json 详细请参考链接BSP自查

[github-actions]

👋 感谢您对 RT-Thread 的贡献！Thank you for your contribution to RT-Thread!

为确保代码符合 RT-Thread 的编码规范，请在你的仓库中执行以下步骤运行代码格式化工作流（如果格式化CI运行失败）。
To ensure your code complies with RT-Thread's coding style, please run the code formatting workflow by following the steps below (If the formatting of CI fails to run).

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如有问题欢迎联系我们，再次感谢您的贡献！💐
If you have any questions, feel free to reach out. Thanks again for your contribution!

[github-actions]

📌 Code Review Assignment

🏷️ Tag: libcpu_riscv

Reviewers: @Yaochenger

Changed Files (Click to expand)

• libcpu/risc-v/common64/mmu.c

🏷️ Tag: workflow

Reviewers: @Rbb666 @kurisaW @supperthomas

Changed Files (Click to expand)

• .github/ALL_BSP_COMPILE.json

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📊 Current Review Status (Last Updated: 2026-08-19 10:39 CST)

• ⌛ @Rbb666 Pending Review
• ⌛ @Yaochenger Pending Review
• ⌛ @kurisaW Pending Review
• ⌛ @supperthomas Pending Review

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📝 Review Instructions

1. 维护者可以通过单击此处来刷新审查状态: 🔄 刷新状态
   Maintainers can refresh the review status by clicking here: 🔄 Refresh Status

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   Comment LGTM/lgtm after confirming approval

3. PR合并前需至少一位维护者确认
   PR must be confirmed by at least one maintainer before merging

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[CLAassistant]

All committers have signed the CLA.

[Rbb666]

@rcitach 帮忙review下，谢谢~

[Rbb666]

https://github.com/RT-Thread/rt-thread/blob/master/.github/ALL_BSP_COMPILE.json#L523

@BadmintonMaster 麻烦添加下ci的编译看护字段

[Copilot]

Pull request overview

This PR adds a new BSP for Xuantie virt64 C908 with RT-Thread Smart (rt-smart) + SMP support, and adjusts the RISC-V common64 MMU implementation to better support SMP user address spaces.

本 PR 新增 Xuantie virt64 C908 的 BSP，并支持 RT-Thread Smart（rt-smart）+ SMP，同时对 RISC-V common64 MMU 做了 SMP 相关适配以更好支持用户态地址空间。

Changes / 变更点：

• Add new BSP bsp/xuantie/virt64/c908 with build scripts, linker scripts, QEMU run script, and basic UART/VirtIO support.
  新增 bsp/xuantie/virt64/c908 BSP（构建脚本、链接脚本、QEMU 运行脚本、UART/VirtIO 基础支持）。
• Update libcpu/risc-v/common64/mmu.c to optimize SMP behavior for user address spaces (share L2/L3, sync L1 across harts; SMP-aware page table allocation/free).
  更新 libcpu/risc-v/common64/mmu.c：面向 SMP 的用户地址空间优化（共享 L2/L3，并在各 hart 间同步 L1；SMP 下页表分配/释放适配）。
• Provide BSP docs in English/Chinese and default configs (.config, rtconfig.h).
  提供中英文 BSP 文档与默认配置（.config、rtconfig.h）。

PR metadata checks / PR 元信息检查：

• PR Title / PR 标题: The current title feat[bsp][xuantie]: c908 support rt-smart; does not follow the repo’s recommended lowercase prefix style like [module][subsystem] Description.
  当前标题不符合仓库建议的前缀格式（如小写的 [module][subsystem] 描述），建议改为类似：[bsp][xuantie] Add virt64 c908 RT-Smart support（示例）。
• CI list claim / CI 列表声明: The PR description indicates the BSP was added to .github/ALL_BSP_COMPILE.json, but no matching entry was found (see review comment).
  PR 描述中勾选了已加入 .github/ALL_BSP_COMPILE.json，但当前未检索到对应条目（见审查评论）。

Reviewed changes

Copilot reviewed 26 out of 26 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
libcpu/risc-v/common64/mmu.c	SMP + rt-smart related MMU/page-table behavior updates for user/kernel spaces
bsp/xuantie/virt64/c908/SConstruct	BSP build entry; generates linker helper scripts and supports Smart linker script
bsp/xuantie/virt64/c908/SConscript	Top-level module aggregation for BSP subdirectories
bsp/xuantie/virt64/c908/run.sh	QEMU run script with C908 CPU selection and optional SMP -smp
bsp/xuantie/virt64/c908/rtconfig.py	Toolchain/build flags for this BSP
bsp/xuantie/virt64/c908/rtconfig.h	Generated configuration header for the provided default config
bsp/xuantie/virt64/c908/README.md	English BSP user guide (build/run, Smart notes)
bsp/xuantie/virt64/c908/README_cn.md	中文 BSP 使用说明（构建/运行、Smart 说明）
bsp/xuantie/virt64/c908/link.lds	Standard edition linker script using generated stack/cpu parameters
bsp/xuantie/virt64/c908/link_smart.lds	Smart edition linker script (high kernel mapping layout)
bsp/xuantie/virt64/c908/link_stacksize.lds	Default stack-size linker include (also regenerated by SCons)
bsp/xuantie/virt64/c908/link_cpus.lds	Default CPU-count linker include (also regenerated by SCons)
bsp/xuantie/virt64/c908/Kconfig	BSP Kconfig entry points and board options
bsp/xuantie/virt64/c908/board/virt.h	VirtIO constants and Smart-only ioremap/mmu includes
bsp/xuantie/virt64/c908/board/SConscript	Driver group build script
bsp/xuantie/virt64/c908/board/Kconfig	VirtIO-related BSP options
bsp/xuantie/virt64/c908/board/drv_virtio.h	VirtIO driver header (placeholder)
bsp/xuantie/virt64/c908/board/drv_virtio.c	VirtIO MMIO device probing and init export
bsp/xuantie/virt64/c908/board/drv_uart.h	NS16550A UART register definitions and interfaces
bsp/xuantie/virt64/c908/board/drv_uart.c	UART serial driver + interrupt hookup; Smart ioremap support
bsp/xuantie/virt64/c908/board/board.h	Board-level memory layout/heap/page region definitions
bsp/xuantie/virt64/c908/board/board.c	Board init: MMU/page init (Smart), interrupts, UART, tick
bsp/xuantie/virt64/c908/applications/SConscript	Applications group build script
bsp/xuantie/virt64/c908/applications/mnt.c	Rootfs mount helper (virtio-blk FAT/ext)
bsp/xuantie/virt64/c908/applications/main.c	Minimal main entry printing banner
bsp/xuantie/virt64/c908/.config	Provided default configuration enabling Smart + SMP and related components

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