linux-kernel - Re: [PATCH V2] arm64: tlbflush: avoid writing RES0 bits

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Date:   Tue, 27 Mar 2018 09:53:16 -0500
From:   Shanker Donthineni <shankerd@...eaurora.org>
To:     Robin Murphy <robin.murphy@....com>,
        Philip Elcan <pelcan@...eaurora.org>,
        linux-arm-kernel@...ts.infradead.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        linux-kernel@...r.kernel.org
Cc:     Thomas Speier <tspeier@...eaurora.org>
Subject: Re: [PATCH V2] arm64: tlbflush: avoid writing RES0 bits


On 03/27/2018 06:34 AM, Robin Murphy wrote:
> On 27/03/18 04:21, Philip Elcan wrote:
>> Several of the bits of the TLBI register operand are RES0 per the ARM
>> ARM, so TLBI operations should avoid writing non-zero values to these
>> bits.
>>
>> This patch adds a macro __TLBI_VADDR(addr, asid) that creates the
>> operand register in the correct format and honors the RES0 bits.
>>
>> Signed-off-by: Philip Elcan <pelcan@...eaurora.org>
>> ---
>>   arch/arm64/include/asm/tlbflush.h | 23 ++++++++++++++++-------
>>   1 file changed, 16 insertions(+), 7 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
>> index 9e82dd7..b1205e9 100644
>> --- a/arch/arm64/include/asm/tlbflush.h
>> +++ b/arch/arm64/include/asm/tlbflush.h
>> @@ -60,6 +60,15 @@
>>           __tlbi(op, (arg) | USER_ASID_FLAG);                \
>>   } while (0)
>>   +/* This macro creates a properly formatted VA operand for the TLBI */
>> +#define __TLBI_VADDR(addr, asid)                \
>> +    ({                            \
>> +        unsigned long __ta = (addr) >> 12;        \
>> +        __ta &= GENMASK_ULL(43, 0);            \
>> +        __ta |= (unsigned long)(asid) << 48;        \
>> +        __ta;                        \
>> +    })
> 
> I'd be inclined to make this a static inline function rather than a macro, since it doesn't need to do any wacky type-dodging, but either way the overall change now looks appropriate;
> 
> Acked-by: Robin Murphy <robin.murphy@....com>
> 

Tested-by: Shanker Donthineni <shankerd@...eaurora.org>

> Thanks,
> Robin.
> 
>> +
>>   /*
>>    *    TLB Management
>>    *    ==============
>> @@ -117,7 +126,7 @@ static inline void flush_tlb_all(void)
>>     static inline void flush_tlb_mm(struct mm_struct *mm)
>>   {
>> -    unsigned long asid = ASID(mm) << 48;
>> +    unsigned long asid = __TLBI_VADDR(0, ASID(mm));
>>         dsb(ishst);
>>       __tlbi(aside1is, asid);
>> @@ -128,7 +137,7 @@ static inline void flush_tlb_mm(struct mm_struct *mm)
>>   static inline void flush_tlb_page(struct vm_area_struct *vma,
>>                     unsigned long uaddr)
>>   {
>> -    unsigned long addr = uaddr >> 12 | (ASID(vma->vm_mm) << 48);
>> +    unsigned long addr = __TLBI_VADDR(uaddr, ASID(vma->vm_mm));
>>         dsb(ishst);
>>       __tlbi(vale1is, addr);
>> @@ -154,8 +163,8 @@ static inline void __flush_tlb_range(struct vm_area_struct *vma,
>>           return;
>>       }
>>   -    start = asid | (start >> 12);
>> -    end = asid | (end >> 12);
>> +    start = __TLBI_VADDR(start, asid);
>> +    end = __TLBI_VADDR(end, asid);
>>         dsb(ishst);
>>       for (addr = start; addr < end; addr += 1 << (PAGE_SHIFT - 12)) {
>> @@ -185,8 +194,8 @@ static inline void flush_tlb_kernel_range(unsigned long start, unsigned long end
>>           return;
>>       }
>>   -    start >>= 12;
>> -    end >>= 12;
>> +    start = __TLBI_VADDR(start, 0);
>> +    end = __TLBI_VADDR(end, 0);
>>         dsb(ishst);
>>       for (addr = start; addr < end; addr += 1 << (PAGE_SHIFT - 12))
>> @@ -202,7 +211,7 @@ static inline void flush_tlb_kernel_range(unsigned long start, unsigned long end
>>   static inline void __flush_tlb_pgtable(struct mm_struct *mm,
>>                          unsigned long uaddr)
>>   {
>> -    unsigned long addr = uaddr >> 12 | (ASID(mm) << 48);
>> +    unsigned long addr = __TLBI_VADDR(uaddr, ASID(mm));
>>         __tlbi(vae1is, addr);
>>       __tlbi_user(vae1is, addr);
>>

-- 
Shanker Donthineni
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.