linux-kernel - Re: [PATCH v3 04/11] x86/mm: Give each mm TLB flush generation a unique ID

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Message-ID: <CALCETrVoRjSL2HncTGQ-PJ_1ycUAV3UcDVMEGw=-f7AbqtEN6w@mail.gmail.com>
Date:   Wed, 21 Jun 2017 08:23:07 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Nadav Amit <nadav.amit@...il.com>,
        Rik van Riel <riel@...hat.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3 04/11] x86/mm: Give each mm TLB flush generation a
 unique ID

On Wed, Jun 21, 2017 at 3:33 AM, Borislav Petkov <bp@...en8.de> wrote:
> On Tue, Jun 20, 2017 at 10:22:10PM -0700, Andy Lutomirski wrote:
>> +#define INIT_MM_CONTEXT(mm)                                          \
>> +     .context = {                                                    \
>> +             .ctx_id = 1,                                            \
>
> So ctx_id of 0 is invalid?
>
> Let's state that explicitly. We could even use it to sanity-check mms or
> whatever.

It's stated explicitly in the comment where it's declared in the same file.

>
>> +     }
>> +
>>  void leave_mm(int cpu);
>>
>>  #endif /* _ASM_X86_MMU_H */
>> diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
>> index ecfcb6643c9b..e5295d485899 100644
>> --- a/arch/x86/include/asm/mmu_context.h
>> +++ b/arch/x86/include/asm/mmu_context.h
>> @@ -129,9 +129,14 @@ static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
>>               this_cpu_write(cpu_tlbstate.state, TLBSTATE_LAZY);
>>  }
>>
>> +extern atomic64_t last_mm_ctx_id;
>
> I think we prefer externs/variable defines at the beginning of the file,
> not intermixed with functions.

Done

>
>> +static inline u64 bump_mm_tlb_gen(struct mm_struct *mm)
>
> inc_mm_tlb_gen() I guess. git grep says like "inc" more :-)

Done

>> +      * that synchronizes with switch_mm: callers are required to order
>
> Please end function names with parentheses.

Done.