From 08f051eda33b51e8ee0f45f05bcfe49d0f0caf6b Mon Sep 17 00:00:00 2001 From: Andrew Waterman Date: Wed, 25 Oct 2017 14:30:32 -0700 Subject: RISC-V: Flush I$ when making a dirty page executable The RISC-V ISA allows for instruction caches that are not coherent WRT stores, even on a single hart. As a result, we need to explicitly flush the instruction cache whenever marking a dirty page as executable in order to preserve the correct system behavior. Local instruction caches aren't that scary (our implementations actually flush the cache, but RISC-V is defined to allow higher-performance implementations to exist), but RISC-V defines no way to perform an instruction cache shootdown. When explicitly asked to do so we can shoot down remote instruction caches via an IPI, but this is a bit on the slow side. Instead of requiring an IPI to all harts whenever marking a page as executable, we simply flush the currently running harts. In order to maintain correct behavior, we additionally mark every other hart as needing a deferred instruction cache which will be taken before anything runs on it. Signed-off-by: Andrew Waterman Signed-off-by: Palmer Dabbelt --- arch/riscv/include/asm/cacheflush.h | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-) (limited to 'arch/riscv/include/asm/cacheflush.h') diff --git a/arch/riscv/include/asm/cacheflush.h b/arch/riscv/include/asm/cacheflush.h index 0595585013b0..5c9ed39ee2a2 100644 --- a/arch/riscv/include/asm/cacheflush.h +++ b/arch/riscv/include/asm/cacheflush.h @@ -18,21 +18,37 @@ #undef flush_icache_range #undef flush_icache_user_range +#undef flush_dcache_page static inline void local_flush_icache_all(void) { asm volatile ("fence.i" ::: "memory"); } +#define PG_dcache_clean PG_arch_1 + +static inline void flush_dcache_page(struct page *page) +{ + if (test_bit(PG_dcache_clean, &page->flags)) + clear_bit(PG_dcache_clean, &page->flags); +} + +/* + * RISC-V doesn't have an instruction to flush parts of the instruction cache, + * so instead we just flush the whole thing. + */ +#define flush_icache_range(start, end) flush_icache_all() +#define flush_icache_user_range(vma, pg, addr, len) flush_icache_all() + #ifndef CONFIG_SMP -#define flush_icache_range(start, end) local_flush_icache_all() -#define flush_icache_user_range(vma, pg, addr, len) local_flush_icache_all() +#define flush_icache_all() local_flush_icache_all() +#define flush_icache_mm(mm, local) flush_icache_all() #else /* CONFIG_SMP */ -#define flush_icache_range(start, end) sbi_remote_fence_i(0) -#define flush_icache_user_range(vma, pg, addr, len) sbi_remote_fence_i(0) +#define flush_icache_all() sbi_remote_fence_i(0) +void flush_icache_mm(struct mm_struct *mm, bool local); #endif /* CONFIG_SMP */ -- cgit v1.2.2 From 921ebd8f2c081b3cf6c3b29ef4103eef3ff26054 Mon Sep 17 00:00:00 2001 From: Andrew Waterman Date: Wed, 25 Oct 2017 14:32:16 -0700 Subject: RISC-V: Allow userspace to flush the instruction cache Despite RISC-V having a direct 'fence.i' instruction available to userspace (which we can't trap!), that's not actually viable when running on Linux because the kernel might schedule a process on another hart. There is no way for userspace to handle this without invoking the kernel (as it doesn't know the thread->hart mappings), so we've defined a RISC-V specific system call to flush the instruction cache. This patch adds both a system call and a VDSO entry. If possible, we'd like to avoid having the system call be considered part of the user-facing ABI and instead restrict that to the VDSO entry -- both just in general to avoid having additional user-visible ABI to maintain, and because we'd prefer that users just call the VDSO entry because there might be a better way to do this in the future (ie, one that doesn't require entering the kernel). Signed-off-by: Andrew Waterman Signed-off-by: Palmer Dabbelt --- arch/riscv/include/asm/cacheflush.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'arch/riscv/include/asm/cacheflush.h') diff --git a/arch/riscv/include/asm/cacheflush.h b/arch/riscv/include/asm/cacheflush.h index 5c9ed39ee2a2..efd89a88d2d0 100644 --- a/arch/riscv/include/asm/cacheflush.h +++ b/arch/riscv/include/asm/cacheflush.h @@ -52,4 +52,10 @@ void flush_icache_mm(struct mm_struct *mm, bool local); #endif /* CONFIG_SMP */ +/* + * Bits in sys_riscv_flush_icache()'s flags argument. + */ +#define SYS_RISCV_FLUSH_ICACHE_LOCAL 1UL +#define SYS_RISCV_FLUSH_ICACHE_ALL (SYS_RISCV_FLUSH_ICACHE_LOCAL) + #endif /* _ASM_RISCV_CACHEFLUSH_H */ -- cgit v1.2.2