Re: [PATCH] RISC-V: Enable Zicbom in usermode

[Conor Dooley]

On Fri, Oct 25, 2024 at 05:15:27PM +0800, Yunhui Cui wrote:
> Like Zicboz, by enabling the corresponding bits of senvcfg,
> the instructions cbo.clean, cbo.flush, and cbo.inval can be
> executed normally in user mode.
> 
> Signed-off-by: Yunhui Cui <cuiyunhui@xxxxxxxxxxxxx>
> ---
>  arch/riscv/kernel/cpufeature.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index 1992ea64786e..bc850518ab41 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -924,7 +924,7 @@ unsigned long riscv_get_elf_hwcap(void)
>  void __init riscv_user_isa_enable(void)
>  {
>  	if (riscv_has_extension_unlikely(RISCV_ISA_EXT_ZICBOZ))
> -		current->thread.envcfg |= ENVCFG_CBZE;
> +		current->thread.envcfg |= ENVCFG_CBIE | ENVCFG_CBCFE | ENVCFG_CBZE;

I believe we previously decided that userspace should not be allowed to
use zicbom, but that not withstanding - this is wrong. It should be
checking for Zicbom, not Zicboz.

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