Re: [PATCH] docs/system: riscv: Update description of CPU

[Palmer Dabbelt]

On Tue, 08 Feb 2022 05:07:23 PST (-0800), liyu.yukiteru@bytedance.com wrote:
> Since the hypervisor extension been non experimental and enabled for
> default CPU, the previous command is no longer available and the
> option `x-h=true` or `h=true` is also no longer required.
>
> Signed-off-by: Yu Li <liyu.yukiteru@bytedance.com>
> ---
>   docs/system/riscv/virt.rst | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/docs/system/riscv/virt.rst b/docs/system/riscv/virt.rst
> index fa016584bf..08ce3c4177 100644
> --- a/docs/system/riscv/virt.rst
> +++ b/docs/system/riscv/virt.rst
> @@ -23,9 +23,9 @@ The ``virt`` machine supports the following devices:
>   * 1 generic PCIe host bridge
>   * The fw_cfg device that allows a guest to obtain data from QEMU
>
> -Note that the default CPU is a generic RV32GC/RV64GC. Optional extensions
> -can be enabled via command line parameters, e.g.: ``-cpu rv64,x-h=true``
> -enables the hypervisor extension for RV64.
> +The hypervisor extension has been enabled for the default CPU, so virtual
> +machines with hypervisor extension can simply be used without explicitly
> +declaring.
>
>   Hardware configuration information
>   ----------------------------------

I saw this landed, but I'm not sure the wording is quite right.  I think 
it's at least missing what is being declared, so something like this

   diff --git a/docs/system/riscv/virt.rst b/docs/system/riscv/virt.rst
   index 08ce3c4177..fe40d6565a 100644
   --- a/docs/system/riscv/virt.rst
   +++ b/docs/system/riscv/virt.rst
   @@ -24,8 +24,8 @@ The ``virt`` machine supports the following devices:
    * The fw_cfg device that allows a guest to obtain data from QEMU
   
    The hypervisor extension has been enabled for the default CPU, so virtual
   -machines with hypervisor extension can simply be used without explicitly
   -declaring.
   +machines with the hypervisor extension can simply be used without explicitly
   +declaring it as enabled.
   
    Hardware configuration information
    ----------------------------------

That said, I think we'd be better off just picking a different example 
extension to enable -- IMO this was less about the hypervisor extension 
and more about the syntax for enabling extensions, that's certianly what 
I end up looking at the docs for.  So IMO we'd be better off with 
something like

   diff --git a/docs/system/riscv/virt.rst b/docs/system/riscv/virt.rst
   index 08ce3c4177..f59e8777b2 100644
   --- a/docs/system/riscv/virt.rst
   +++ b/docs/system/riscv/virt.rst
   @@ -23,9 +23,9 @@ The ``virt`` machine supports the following devices:
    * 1 generic PCIe host bridge
    * The fw_cfg device that allows a guest to obtain data from QEMU
   
   -The hypervisor extension has been enabled for the default CPU, so virtual
   -machines with hypervisor extension can simply be used without explicitly
   -declaring.
   +Note that the default CPU is a generic RV32GC/RV64GC. Optional extensions
   +can be enabled via command line parameters, e.g.: ``-cpu rv64,c=false``
   +disables the C extension.
   
    Hardware configuration information
    ----------------------------------