From: Arnd Bergmann <arnd@arndb.de>
To: Gregory CLEMENT <gregory.clement@bootlin.com>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
Russell King <linux@armlinux.org.uk>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v2 4/6] ARM: mm: Aligned pte allocation to one page
Date: Fri, 12 Jun 2020 10:37:15 +0200 [thread overview]
Message-ID: <CAK8P3a2-g9ZmFiWJ_i4-0C6=WwzC1UjHGzY07w4y=0O1pHSX5Q@mail.gmail.com> (raw)
In-Reply-To: <20200611134914.765827-5-gregory.clement@bootlin.com>
On Thu, Jun 11, 2020 at 3:49 PM Gregory CLEMENT
<gregory.clement@bootlin.com> wrote:
>
> In pte_offset_kernel() the pte_index macro is used. This macro makes
> the assumption that the address is aligned to a page size.
>
> In arm_pte_allocation, the size allocated is the size needed for 512
> entries. Actually this size was calculated to fit in a 4K page. When
> using larger page, the size of the table allocated is no more
> aligned which end to give a wrong physical address.
>
> The solution is to round up the allocation to a page size instead of
> the exact size of the tables (which is 4KB). It allows to comply with
> the assumption of pte_index() but the drawback is a waste of memory
> for the early allocation if page size is bigger than 4KB.
Have you considered increasing PTRS_PER_PTE instead to fill up
a logical page instead? If that doesn't work, can you explain here
why not?
Arnd
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next prev parent reply other threads:[~2020-06-12 8:37 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-11 13:49 [PATCH v2 0/6] ARM: Add support for large kernel page (from 8K to 64K) Gregory CLEMENT
2020-06-11 13:49 ` [PATCH v2 1/6] ARM: Use PAGE_SIZE for ELF_EXEC_PAGESIZE Gregory CLEMENT
2020-06-12 8:22 ` Arnd Bergmann
2020-06-12 8:35 ` Russell King - ARM Linux admin
2020-06-12 8:46 ` Arnd Bergmann
2020-06-12 8:50 ` Russell King - ARM Linux admin
2020-06-12 11:50 ` Catalin Marinas
2020-06-12 12:06 ` Gregory CLEMENT
2020-06-12 8:52 ` Gregory CLEMENT
2020-06-11 13:49 ` [PATCH v2 2/6] ARM: pagetable: prepare hardware page table to use large page Gregory CLEMENT
2020-06-11 13:49 ` [PATCH v2 3/6] ARM: Make the number of fix bitmap depend on the page size Gregory CLEMENT
2020-06-11 13:49 ` [PATCH v2 4/6] ARM: mm: Aligned pte allocation to one page Gregory CLEMENT
2020-06-12 8:37 ` Arnd Bergmann [this message]
2020-06-12 10:25 ` Catalin Marinas
2020-06-12 11:56 ` Gregory CLEMENT
2020-06-11 13:49 ` [PATCH v2 5/6] ARM: Add large kernel page support Gregory CLEMENT
2020-06-11 13:49 ` [PATCH v2 6/6] ARM: Add 64K page support at MMU level Gregory CLEMENT
2020-06-11 16:21 ` [PATCH v2 0/6] ARM: Add support for large kernel page (from 8K to 64K) Russell King - ARM Linux admin
2020-06-12 9:15 ` Gregory CLEMENT
2020-06-12 9:23 ` Arnd Bergmann
2020-06-12 12:21 ` Catalin Marinas
2020-06-12 12:49 ` Arnd Bergmann
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