Hi Atish, Am Samstag, 22. Januar 2022, 04:45:52 CET schrieb Atish Patra: > 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. ok, I'll roll this back to simply fixing the null-ptr issue. Meanwhile I even found a nicer solution without actually touching the cachflush code. Without sbi_init() we can assume that we're still before smp bringup, so the local_flush_icache_all() in flush_icache_all() will do the trick just fine and sbi_remote_fence_i() simply just needs to be an empty function until sbi is initialized. Heiko > > > 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 > > > >
