Re: [PATCH 09/15] riscv: implement remote sfence.i natively for M-mode

Atish Patra
2019-08-20T21:05:00Z

On Tue, 2019-08-13 at 17:47 +0200, Christoph Hellwig wrote:
> The RISC-V ISA only supports flushing the instruction cache for the
> local
> CPU core. For normal S-mode Linux remote flushing is offloaded to
> machine mode using ecalls, but for M-mode Linux we'll have to do it
> ourselves. Use the same implementation as all the existing open
> source
> SBI implementations by just doing an IPI to all remote cores to
> execute
> th sfence.i instruction on every live core.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> arch/riscv/mm/cacheflush.c | 31 +++++++++++++++++++++++++++----
> 1 file changed, 27 insertions(+), 4 deletions(-)
>
> diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
> index 9ebcff8ba263..10875ea1065e 100644
> --- a/arch/riscv/mm/cacheflush.c
> +++ b/arch/riscv/mm/cacheflush.c
> @@ -10,10 +10,35 @@
>
> #include <asm/sbi.h>
>
> +#ifdef CONFIG_M_MODE
> +static void ipi_remote_fence_i(void *info)
> +{
> + return local_flush_icache_all();
> +}
> +
> +void flush_icache_all(void)
> +{
> + on_each_cpu(ipi_remote_fence_i, NULL, 1);
> +}
> +
> +static void flush_icache_cpumask(const cpumask_t *mask)
> +{
> + on_each_cpu_mask(mask, ipi_remote_fence_i, NULL, 1);
> +}
> +#else /* CONFIG_M_MODE */
> void flush_icache_all(void)
> {
> sbi_remote_fence_i(NULL);
> }
> +static void flush_icache_cpumask(const cpumask_t *mask)
> +{
> + cpumask_t hmask;
> +
> + cpumask_clear(&hmask);
> + riscv_cpuid_to_hartid_mask(mask, &hmask);
> + sbi_remote_fence_i(hmask.bits);
> +}
> +#endif /* CONFIG_M_MODE */
>
> /*
> * Performs an icache flush for the given MM context. RISC-V has no
> direct
> @@ -28,7 +53,7 @@ void flush_icache_all(void)
> void flush_icache_mm(struct mm_struct *mm, bool local)
> {
> unsigned int cpu;
> - cpumask_t others, hmask, *mask;
> + cpumask_t others, *mask;
>
> preempt_disable();
>
> @@ -47,9 +72,7 @@ void flush_icache_mm(struct mm_struct *mm, bool
> local)
> cpumask_andnot(&others, mm_cpumask(mm), cpumask_of(cpu));
> local |= cpumask_empty(&others);
> if (mm != current->active_mm || !local) {
> - cpumask_clear(&hmask);
> - riscv_cpuid_to_hartid_mask(&others, &hmask);
> - sbi_remote_fence_i(hmask.bits);
> + flush_icache_cpumask(&others);
> } else {
> /*
> * It's assumed that at least one strongly ordered
> operation is

Reviewed-by: Atish Patra <atish.patra@wdc.com>

--
Regards,
Atish