From 11f769039e1d10652bb45e83ecaad18a8681d5e5 Mon Sep 17 00:00:00 2001 From: James Hogan Date: Wed, 13 Jul 2016 14:12:56 +0100 Subject: [PATCH] MIPS: c-r4k: Use SMP calls for CM indexed cache ops The MIPS Coherence Manager (CM) can propagate address-based ("hit") cache operations to other cores in the coherent system, alleviating software of the need to use SMP calls, however indexed cache operations are not propagated by hardware since doing so makes no sense for separate caches. Update r4k_op_needs_ipi() to report that only hit cache operations are globalized by the CM, requiring indexed cache operations to be globalized by software via an SMP call. r4k_on_each_cpu() previously had a special case for CONFIG_MIPS_MT_SMP, intended to avoid the SMP calls when the only other CPUs in the system were other VPEs in the same core, and hence sharing the same caches. This was changed by commit cccf34e9411c ("MIPS: c-r4k: Fix cache flushing for MT cores") to apparently handle multi-core multi-VPE systems, but it focussed mainly on hit cache ops, so the SMP calls were still disabled entirely for CM systems. This doesn't normally cause problems, but tests can be written to hit these corner cases by using multiple threads, or changing task affinities to force the process to migrate cores. For example the failure of mprotect RW->RX to globally sync icaches (via flush_cache_range) can be detected by modifying and mprotecting a code page on one core, and migrating to a different core to execute from it. Signed-off-by: James Hogan Cc: Paul Burton Cc: Leonid Yegoshin Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/13807/ Signed-off-by: Ralf Baechle --- arch/mips/mm/c-r4k.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/mips/mm/c-r4k.c b/arch/mips/mm/c-r4k.c index 8016bab..3227a0a 100644 --- a/arch/mips/mm/c-r4k.c +++ b/arch/mips/mm/c-r4k.c @@ -68,7 +68,7 @@ static inline bool r4k_op_needs_ipi(unsigned int type) { /* The MIPS Coherence Manager (CM) globalizes address-based cache ops */ - if (mips_cm_present()) + if (type == R4K_HIT && mips_cm_present()) return false; /* -- 2.7.4