linux-kernel - Re: [PATCH] [9/9] GBPAGES: Do kernel direct mapping at boot using GB pages

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Date:	Thu, 31 Jan 2008 17:17:41 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andi Kleen <ak@...e.de>
cc:	mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [9/9] GBPAGES: Do kernel direct mapping at boot using
 GB pages

On Tue, 29 Jan 2008, Andi Kleen wrote:
>
> +static unsigned long direct_entry(unsigned long paddr)

Please use a more sensible function name. This one has no association
with the functionality at all.

> +{
> +	unsigned long entry;

New line please

> +	entry = __PAGE_KERNEL_LARGE|paddr;
> +	entry &= __supported_pte_mask;
> +	return entry;
> +}

> +static void init_gbpages(void)
> +{
> +#ifdef CONFIG_DEBUG_PAGEALLOC
> +	/* debug pagealloc causes too much recursion with gbpages */
> +	if (direct_gbpages == 0)
> +		return;
> +#endif
> +	if (direct_gbpages >= 0 && cpu_has_gbpages) {
> +		printk(KERN_INFO "Using GB pages for direct mapping\n");
> +		direct_gbpages = 1;
> +	} else
> +		direct_gbpages = 0;
> +}

Please use simple boolean logic. gbpages are either enabled or disabled.

> +static void split_gb_page(pud_t *pud, unsigned long paddr)
> +{
> +	int i;
> +	pmd_t *pmd;
> +	struct page *p = alloc_page(GFP_KERNEL);
> +	if (!p)
> +		return;
> +
> +	paddr &= PUD_PAGE_MASK;
> +	pmd = page_address(p);
> +	for (i = 0; i < PTRS_PER_PTE; i++, paddr += PMD_PAGE_SIZE)
> +		pmd[i] = __pmd(direct_entry(paddr));
> +	pud_populate(NULL, pud, pmd);
> +}
> +
>  /*
>   * Unmap a kernel mapping if it exists. This is useful to avoid
>   * prefetches from the CPU leading to inconsistent cache lines.
> @@ -467,6 +511,8 @@ __clear_kernel_mapping(unsigned long add
>  			continue;
>  
>  		pud = pud_offset(pgd, address);
> +		if (pud_large(*pud))
> +			split_gb_page(pud, __pa(address));
>  		if (pud_none(*pud))
>  			continue;

As I said before, this needs to use CPA and not implement another variant.

Thanks,
	tglx
  
 
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