[PATCH] implement flush_cache_vmap for RISC-V
Alex Ghiti
alex at ghiti.fr
Wed Apr 14 08:03:13 BST 2021
Hi,
Le 4/12/21 à 3:08 AM, Jisheng Zhang a écrit :
> Hi Jiuyang,
>
> On Mon, 12 Apr 2021 00:05:30 +0000 Jiuyang Liu <liu at jiuyang.me> wrote:
>
>
>>
>> This patch implements flush_cache_vmap for RISC-V, since it modifies PTE.
>> Without this patch, SFENCE.VMA won't be added to related codes, which
>> might introduce a bug in the out-of-order micro-architecture
>> implementations.
>>
>> Signed-off-by: Jiuyang Liu <liu at jiuyang.me>
>> Reviewed-by: Alexandre Ghiti <alex at ghiti.fr>
>> Reviewed-by: Palmer Dabbelt <palmer at dabbelt.com>
>
> IIRC, Palmer hasn't given this Reviewed-by tag.
>
>> ---
>
> Could you plz add version and changes? IIRC, this is the v3.
>
>> arch/riscv/include/asm/cacheflush.h | 6 ++++++
>> 1 file changed, 6 insertions(+)
>>
>> diff --git a/arch/riscv/include/asm/cacheflush.h b/arch/riscv/include/asm/cacheflush.h
>> index 23ff70350992..3fd528badc35 100644
>> --- a/arch/riscv/include/asm/cacheflush.h
>> +++ b/arch/riscv/include/asm/cacheflush.h
>> @@ -30,6 +30,12 @@ static inline void flush_dcache_page(struct page *page)
>> #define flush_icache_user_page(vma, pg, addr, len) \
>> flush_icache_mm(vma->vm_mm, 0)
>>
>> +/*
>> + * flush_cache_vmap is invoked after map_kernel_range() has installed the page
>> + * table entries, which modifies PTE, SFENCE.VMA should be inserted.
>
> Just my humble opinion, flush_cache_vmap() may not be necessary. vmalloc_fault
> can take care of this, and finally sfence.vma is inserted in related path.
>
I believe Palmer and Jisheng are right, my initial proposal to implement
flush_cache_vmap is wrong.
But then, Jiuyang should not have noticed any problem here, so what's
wrong? @Jiuyang: Does implementing flush_cache_vmap fix your issue?
And regarding flush_cache_vunmap, from Jisheng call stack, it seems also
not necessary.
@Jiuyang: Can you tell us more about what you noticed?
> Regards
>
>> + */
>> +#define flush_cache_vmap(start, end) flush_tlb_all()
>> +
>> #ifndef CONFIG_SMP
>>
>> #define flush_icache_all() local_flush_icache_all()
>> --
>> 2.31.1
>
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