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

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Date:   Tue, 27 Mar 2018 12:34:37 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     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>,
        Shanker Donthineni <shankerd@...eaurora.org>
Subject: Re: [PATCH V2] arm64: tlbflush: avoid writing RES0 bits

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>

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);
>