On Tue, Jan 19, 2021 at 4:45 PM Vincenzo Frascino <vincenzo.frasc...@arm.com> wrote: > > Hi Catalin, > > On 1/19/21 2:45 PM, Catalin Marinas wrote: > > On Mon, Jan 18, 2021 at 06:30:33PM +0000, Vincenzo Frascino wrote: > >> mte_assign_mem_tag_range() is called on production KASAN HW hot > >> paths. It makes sense to inline it in an attempt to reduce the > >> overhead. > >> > >> Inline mte_assign_mem_tag_range() based on the indications provided at > >> [1]. > >> > >> [1] > >> https://lore.kernel.org/r/caaehk+wco+j7d1_t89dg+jjrplk3x9rsgfkxjgd0zcufjqt...@mail.gmail.com/ > >> > >> Cc: Catalin Marinas <catalin.mari...@arm.com> > >> Cc: Will Deacon <w...@kernel.org> > >> Signed-off-by: Vincenzo Frascino <vincenzo.frasc...@arm.com> > >> --- > >> arch/arm64/include/asm/mte.h | 26 +++++++++++++++++++++++++- > >> arch/arm64/lib/mte.S | 15 --------------- > >> 2 files changed, 25 insertions(+), 16 deletions(-) > >> > >> diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h > >> index 237bb2f7309d..1a6fd53f82c3 100644 > >> --- a/arch/arm64/include/asm/mte.h > >> +++ b/arch/arm64/include/asm/mte.h > >> @@ -49,7 +49,31 @@ long get_mte_ctrl(struct task_struct *task); > >> int mte_ptrace_copy_tags(struct task_struct *child, long request, > >> unsigned long addr, unsigned long data); > >> > >> -void mte_assign_mem_tag_range(void *addr, size_t size); > >> +static inline void mte_assign_mem_tag_range(void *addr, size_t size) > >> +{ > >> + u64 _addr = (u64)addr; > >> + u64 _end = _addr + size; > >> + > >> + /* > >> + * This function must be invoked from an MTE enabled context. > >> + * > >> + * Note: The address must be non-NULL and MTE_GRANULE_SIZE aligned and > >> + * size must be non-zero and MTE_GRANULE_SIZE aligned. > >> + */ > >> + do { > >> + /* > >> + * 'asm volatile' is required to prevent the compiler to move > >> + * the statement outside of the loop. > >> + */ > >> + asm volatile(__MTE_PREAMBLE "stg %0, [%0]" > >> + : > >> + : "r" (_addr) > >> + : "memory"); > >> + > >> + _addr += MTE_GRANULE_SIZE; > >> + } while (_addr != _end); > >> +} > > > > While I'm ok with moving this function to C, I don't think it solves the > > inlining in the kasan code. The only interface we have to kasan is via > > mte_{set,get}_mem_tag_range(), so the above function doesn't need to > > live in a header. > > > > If you do want inlining all the way to the kasan code, we should > > probably move the mte_{set,get}_mem_tag_range() functions to the header > > as well (and ideally backed by some numbers to show that it matters). > > > > Moving it to mte.c also gives us more control on how it's called (we > > have the WARN_ONs in place in the callers). > > > > Based on the thread [1] this patch contains only an intermediate step to allow > KASAN to call directly mte_assign_mem_tag_range() in future. At that point I > think that mte_set_mem_tag_range() can be removed. > > If you agree, I would live the things like this to give to Andrey a chance to > execute on the original plan with a separate series.
I think we should drop this patch from this series as it's unrelated. I will pick it up into my future optimization series. Then it will be easier to discuss it in the context. The important part that I needed is an inlinable C implementation of mte_assign_mem_tag_range(), which I now have with this patch. Thanks, Vincenzo!