Re: [PATCH v2 01/17] xen/riscv: implement sbi_remote_hfence_gvma()

[Jan Beulich <jbeulich@xxxxxxxx>]

On 10.06.2025 15:05, Oleksii Kurochko wrote:
> Instruct the remote harts to execute one or more HFENCE.GVMA instructions,
> covering the range of guest physical addresses between start_addr and
> start_addr + size for all the guests.

Here and in the code comment: Why "for all the guests"? Under what conditions
would you require such a broad (guest) TLB flush?

> --- a/xen/arch/riscv/sbi.c
> +++ b/xen/arch/riscv/sbi.c
> @@ -258,6 +258,15 @@ int sbi_remote_sfence_vma(const cpumask_t *cpu_mask, 
> vaddr_t start,
>                        cpu_mask, start, size, 0, 0);
>  }
>  
> +int sbi_remote_hfence_gvma(const cpumask_t *cpu_mask, vaddr_t start,
> +                           size_t size)
> +{
> +    ASSERT(sbi_rfence);

As previously indicated, I question the usefulness of such assertions. If the
pointer is still NULL, ...

> +    return sbi_rfence(SBI_EXT_RFENCE_REMOTE_HFENCE_GVMA,
> +                      cpu_mask, start, size, 0, 0);

... you'll crash here anyway (much like you will in a release build).

Jan