linux-kernel - Re: [PATCHv3 5/6] arm64: Use __pa

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Date:   Fri, 18 Nov 2016 14:35:44 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Laura Abbott <labbott@...hat.com>, lorenzo.pieralisi@....com
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCHv3 5/6] arm64: Use __pa_symbol for kernel symbols

Hi Laura,

On Thu, Nov 17, 2016 at 05:16:55PM -0800, Laura Abbott wrote:
> 
> __pa_symbol is technically the marco that should be used for kernel
> symbols. Switch to this as a pre-requisite for DEBUG_VIRTUAL which
> will do bounds checking.
> 
> Signed-off-by: Laura Abbott <labbott@...hat.com>
> ---
> v3: Conversion of more sites besides just _end. Addition of __lm_sym_addr
> macro to take care of the _va(__pa_symbol(..)) idiom.
> 
> Note that a copy of __pa_symbol was added to avoid a mess of headers
> since the #ifndef __pa_symbol case is defined in linux/mm.h

I think we also need to fix up virt_to_phys(__cpu_soft_restart) in
arch/arm64/kernel/cpu-reset.h. Otherwise, this looks complete for uses
falling under arch/arm64/.

I also think it's worth mentioning in the commit message that this patch
adds and __lm_sym_addr() and uses it in some places so that low-level
helpers can use virt_to_phys() or __pa() consistently.

The PSCI change doesn't conflict with patches [1] that'll go via
arm-soc, so I'm happy for that PSCI change to go via the arm64 tree,
though it may be worth splitting into its own patch just in case
something unexpected crops up.

With those fixed up:

Reviewed-by: Mark Rutland <mark.rutland@....com>

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2016-November/466522.html

Otherwise, I just have a few nits below.

> @@ -271,7 +271,7 @@ static inline void __kvm_flush_dcache_pud(pud_t pud)
>  	kvm_flush_dcache_to_poc(page_address(page), PUD_SIZE);
>  }
>  
> -#define kvm_virt_to_phys(x)		__virt_to_phys((unsigned long)(x))
> +#define kvm_virt_to_phys(x)		__pa_symbol((unsigned long)(x))

Nit: we can drop the unsigned long cast given __pa_symbol() contains
one.

> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index ffbb9a5..c2041a3 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -52,7 +52,7 @@ extern void __pgd_error(const char *file, int line, unsigned long val);
>   * for zero-mapped memory areas etc..
>   */
>  extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
> -#define ZERO_PAGE(vaddr)	pfn_to_page(PHYS_PFN(__pa(empty_zero_page)))
> +#define ZERO_PAGE(vaddr)	pfn_to_page(PHYS_PFN(__pa_symbol(empty_zero_page)))

Nit: I think we can also simplify this to:

	phys_to_page(__pa_symbol(empty_zero_page))

... since phys_to_page(p) is (pfn_to_page(__phys_to_pfn(p)))
... and __phys_to_pfn(p) is PHYS_PFN(p)

> diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
> index 6f2ac4f..af8967a 100644
> --- a/arch/arm64/kernel/insn.c
> +++ b/arch/arm64/kernel/insn.c
> @@ -97,7 +97,7 @@ static void __kprobes *patch_map(void *addr, int fixmap)
>  	if (module && IS_ENABLED(CONFIG_DEBUG_SET_MODULE_RONX))
>  		page = vmalloc_to_page(addr);
>  	else if (!module)
> -		page = pfn_to_page(PHYS_PFN(__pa(addr)));
> +		page = pfn_to_page(PHYS_PFN(__pa_symbol(addr)));

Nit: likewise, we can use phys_to_page() here.

> diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
> index a2c2478..791e87a 100644
> --- a/arch/arm64/kernel/vdso.c
> +++ b/arch/arm64/kernel/vdso.c
> @@ -140,11 +140,11 @@ static int __init vdso_init(void)
>  		return -ENOMEM;
>  
>  	/* Grab the vDSO data page. */
> -	vdso_pagelist[0] = pfn_to_page(PHYS_PFN(__pa(vdso_data)));
> +	vdso_pagelist[0] = pfn_to_page(PHYS_PFN(__pa_symbol(vdso_data)));

Nit: phys_to_page() again.

>  
>  	/* Grab the vDSO code pages. */
>  	for (i = 0; i < vdso_pages; i++)
> -		vdso_pagelist[i + 1] = pfn_to_page(PHYS_PFN(__pa(&vdso_start)) + i);
> +		vdso_pagelist[i + 1] = pfn_to_page(PHYS_PFN(__pa_symbol(&vdso_start)) + i);

Nit: phys_to_page() again.

Thanks,
Mark.