From: catalin.marinas@arm•com (Catalin Marinas)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v4] ARM: LPAE: Fix mapping in alloc_init_pte for unaligned addresses
Date: Wed, 6 Feb 2013 15:16:38 +0000 [thread overview]
Message-ID: <20130206151638.GG26454@arm.com> (raw)
In-Reply-To: <511260FC.2090002@ti.com>
On Wed, Feb 06, 2013 at 01:56:12PM +0000, R Sricharan wrote:
> On Wednesday 06 February 2013 05:45 PM, Catalin Marinas wrote:
> > On Mon, Feb 04, 2013 at 04:44:19AM +0000, R Sricharan wrote:
> >> I did a similar kind of patch in my V1 [1].
> >> I should be using PMD_MASK instead of SECTION_MASK there, and
> >> updated it in the next version.
> >>
> >> [1] https://patchwork.kernel.org/patch/1272991/
> >
> > With regards to your current patch, I really don't think looping over
> > pmd in alloc_init_pte() is the right fix. The alloc_init_pte() function
> > gets a pmd argument and it is supposed to make it point to a pte and
> > populate that pte rather than populate a number of pmds.
> >
> > create_mapping() loops over pgds. alloc_init_pud() loops over puds
> > (well, we don't have any but we have the function for consistency).
> > alloc_init_section() should loop over pmds (we can even change the name
> > to alloc_init_pmd()).
> >
> > Your original patch from August was better as it kept the looping
> > consistent but as you said, it should be using pmd_addr_end(). We can
> > use something simpler like alloc_init_pmd() on arm64 and instead of
> > set_pmd() there just call a separate map_init_section() which for
> > 2-levels it sets both entries. This may address Russell's comment that
> > the resulting code was ugly.
>
> Thanks. So just to understand, you mean alloc_init_pmd loops over
> map_init_section. map_init_section populates either one pmd
> or calls alloc_init_pte. correct ? . I can send a v5 for this.
alloc_init_pmd() loops over pmd (similar to alloc_init_pud). If
(type->prot_sect && ((addr | next | phys) & ~SECTION_MASK) == 0) you
call a map_init_section (whatever name you think is better) function
which contains the current section code from alloc_init_section().
Something like below (easier than explaining):
static void __init map_init_section(pmd_t *pmd, unsigned long addr,
unsigned long end, phys_addr_t phys,
const struct mem_type *type)
{
#ifndef CONFIG_ARM_LPAE
if (addr & SECTION_SIZE)
pmd++;
#endif
do {
*pmd = __pmd(phys | type->prot_sect);
phys += SECTION_SIZE;
} while (pmd++, addr += SECTION_SIZE, addr != end);
flush_pmd_entry(p);
}
Pretty much avoiding the indentation level in alloc_init_section() with
multiple loops.
> > The problem with the classic MMU is that if we have a 1MB range we can
> > end up with just page mappings. The code is currently buggy since if we
> > have create_mapping() for a 1MB range and later create_mapping() for a
> > 4KB in the next MB, the first 1MB is removed.
>
> Ok, so in that case we will have a BUG_ON(pmd_bad) right?
Yes, you are right, the BUG_ON(pmd_bad) should catch this. The other
scenario (4K mapping followed by 1M) wouldn't be but it's relatively
safe as we don't override any entry.
--
Catalin
next prev parent reply other threads:[~2013-02-06 15:16 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-29 15:07 [PATCH v4] ARM: LPAE: Fix mapping in alloc_init_pte for unaligned addresses R Sricharan
2013-02-01 6:21 ` Santosh Shilimkar
2013-02-01 16:26 ` Catalin Marinas
2013-02-01 16:32 ` Christoffer Dall
2013-02-01 16:37 ` Catalin Marinas
2013-02-01 16:40 ` Christoffer Dall
2013-02-01 17:42 ` Catalin Marinas
2013-02-01 18:37 ` Christoffer Dall
2013-02-04 4:40 ` R Sricharan
2013-02-04 4:44 ` R Sricharan
2013-02-04 11:10 ` R Sricharan
2013-02-06 12:15 ` Catalin Marinas
2013-02-06 12:22 ` Russell King - ARM Linux
2013-02-06 12:33 ` Catalin Marinas
2013-02-06 13:59 ` R Sricharan
2013-02-06 13:56 ` R Sricharan
2013-02-06 15:16 ` Catalin Marinas [this message]
2013-02-06 15:25 ` R Sricharan
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