On Fri, Jan 21, 2022 at 8:37 AM Heiko Stuebner <heiko@xxxxxxxxx> wrote: > > Right now, the flush_icache functions always use the SBI remote-fence > when SBI is available, leaving using IPIs as a fallback mechanism. > > IPIs on the other hand are more flexible, as the ipi_ops are initially > set to go through SBI but later will be overwritten to go through the > ACLINT/CLINT. > > In a discussion we had, Nick was of the opinion that "In general we > should prefer doing IPIs on S-mode through CLINT instead of going > through SBI/M-mode, Yes. Once Anup's ACLINT drivers are merged, that should be the preferred approach. https://github.com/avpatel/linux/commit/416c667fd77d6f1fc310cbf727ec127aaf96cae2 >so IMHO we should only be using > on_each_cpu_mask(ipi_remote_fence_i) on flush_icache_all()/ > flush_icache_mm() and remove any explicit calls to sbi_remote_fence_i(), That's a bit confusing because we will be using SBI calls for all other fences while using IPIs for fence.i > because this way we continue using SBI for doing remote fences even after > CLINT/ACLINT driver is registered, instead of using direct IPIs through > CLINT/ACLINT." > > So follow this suggestion and just do ipi calls to have the proper kernel > parts do them, > > This also fixes the null-ptr dereference happening when flush_icache_all() > is called before sbi_init(). > IMHO, this series should only fix the null-ptr dereference issue. The IPI based fence (for all) should only be disabled along with the ACLINT driver that actually enables S-mode IPIs. > Suggested-by: Nick Kossifidis <mick@xxxxxxxxxxxx> > Signed-off-by: Heiko Stuebner <heiko@xxxxxxxxx> > --- > arch/riscv/mm/cacheflush.c | 8 +------- > 1 file changed, 1 insertion(+), 7 deletions(-) > > diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c > index 6cb7d96ad9c7..c35375cd52ec 100644 > --- a/arch/riscv/mm/cacheflush.c > +++ b/arch/riscv/mm/cacheflush.c > @@ -17,11 +17,7 @@ static void ipi_remote_fence_i(void *info) > void flush_icache_all(void) > { > local_flush_icache_all(); > - > - if (IS_ENABLED(CONFIG_RISCV_SBI)) > - sbi_remote_fence_i(NULL); > - else > - on_each_cpu(ipi_remote_fence_i, NULL, 1); > + on_each_cpu(ipi_remote_fence_i, NULL, 1); > } > EXPORT_SYMBOL(flush_icache_all); > > @@ -66,8 +62,6 @@ void flush_icache_mm(struct mm_struct *mm, bool local) > * with flush_icache_deferred(). > */ > smp_mb(); > - } else if (IS_ENABLED(CONFIG_RISCV_SBI)) { > - sbi_remote_fence_i(&others); > } else { > on_each_cpu_mask(&others, ipi_remote_fence_i, NULL, 1); > } > -- > 2.30.2 > > > _______________________________________________ > linux-riscv mailing list > linux-riscv@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-riscv -- Regards, Atish
