linux-kernel - Re: [RFC PATCH 3/7] mm: Change ioremap to set up huge I/O mappings

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Message-Id: <20150126155811.0ade183f5f3f89277d11fde6@linux-foundation.org>
Date:	Mon, 26 Jan 2015 15:58:11 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Toshi Kani <toshi.kani@...com>
Cc:	hpa@...or.com, tglx@...utronix.de, mingo@...hat.com, arnd@...db.de,
	linux-mm@...ck.org, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 3/7] mm: Change ioremap to set up huge I/O mappings

On Mon, 26 Jan 2015 16:13:25 -0700 Toshi Kani <toshi.kani@...com> wrote:

> Change ioremap_pud_range() and ioremap_pmd_range() to set up
> huge I/O mappings when their capability is enabled and their
> conditions are met in a given request -- both virtual & physical
> addresses are aligned and its range fufills the mapping size.
> 
> These changes are only enabled when both CONFIG_HUGE_IOMAP
> and CONFIG_HAVE_ARCH_HUGE_VMAP are defined.
> 
> --- a/lib/ioremap.c
> +++ b/lib/ioremap.c
> @@ -81,6 +81,14 @@ static inline int ioremap_pmd_range(pud_t *pud, unsigned long addr,
>  		return -ENOMEM;
>  	do {
>  		next = pmd_addr_end(addr, end);
> +
> +		if (ioremap_pmd_enabled() &&
> +		    ((next - addr) == PMD_SIZE) &&
> +		    !((phys_addr + addr) & (PMD_SIZE-1))) {

IS_ALIGNED might be a little neater here.

> +			pmd_set_huge(pmd, phys_addr + addr, prot);
> +			continue;
> +		}
> +
>  		if (ioremap_pte_range(pmd, addr, next, phys_addr + addr, prot))
>  			return -ENOMEM;
>  	} while (pmd++, addr = next, addr != end);
> @@ -99,6 +107,14 @@ static inline int ioremap_pud_range(pgd_t *pgd, unsigned long addr,
>  		return -ENOMEM;
>  	do {
>  		next = pud_addr_end(addr, end);
> +
> +		if (ioremap_pud_enabled() &&
> +		    ((next - addr) == PUD_SIZE) &&
> +		    !((phys_addr + addr) & (PUD_SIZE-1))) {

And here.

> +			pud_set_huge(pud, phys_addr + addr, prot);
> +			continue;
> +		}
> +
>  		if (ioremap_pmd_range(pud, addr, next, phys_addr + addr, prot))
>  			return -ENOMEM;
>  	} while (pud++, addr = next, addr != end);
--
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