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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Alex Ghiti <alex@ghiti.fr>, Palmer Dabbelt <palmer@dabbelt.com>
Cc: mpe@ellerman.id.au, paulus@samba.org,
	Paul Walmsley <paul.walmsley@sifive.com>,
	aou@eecs.berkeley.edu, Anup Patel <Anup.Patel@wdc.com>,
	Atish Patra <Atish.Patra@wdc.com>,
	zong.li@sifive.com, linux-kernel@vger.kernel.org,
	linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
	linux-mm@kvack.org
Subject: Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone
Date: Fri, 24 Jul 2020 08:33:12 +1000	[thread overview]
Message-ID: <418d5f3d3f42bbc79c5cf30e18ec89edfe2dbd26.camel@kernel.crashing.org> (raw)
In-Reply-To: <cade70e2-0179-2650-41c5-036679aaf30c@ghiti.fr>

On Thu, 2020-07-23 at 01:21 -0400, Alex Ghiti wrote:
> > works fine with huge pages, what is your problem there ? You rely on
> > punching small-page size holes in there ?
> > 
> 
> ARCH_HAS_STRICT_KERNEL_RWX prevents the use of a hugepage for the kernel 
> mapping in the direct mapping as it sets different permissions to 
> different part of the kernel (data, text..etc).

Ah ok, that can be solved in a couple of ways...

One is to use the linker script to ensure those sections are linked
HUGE_PAGE_SIZE appart and moved appropriately by early boot code. One
is to selectively degrade just those huge pages.

I'm not familiar with the RiscV MMU (I should probably go have a look)
but if it's a classic radix tree with huge pages at PUD/PMD level, then
you could just degrade the one(s) that cross those boundaries.

Cheers,
Ben.



  reply	other threads:[~2020-07-23 22:34 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-07  7:59 [PATCH v5 0/4] vmalloc kernel mapping and relocatable kernel Alexandre Ghiti
2020-06-07  7:59 ` [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone Alexandre Ghiti
2020-06-11 21:34   ` Atish Patra
2020-06-12 12:30     ` Alex Ghiti
2020-07-09  5:05   ` Palmer Dabbelt
2020-07-09  8:15     ` Zong Li
2020-07-09 11:11     ` Alex Ghiti
2020-07-21 18:36       ` Alex Ghiti
2020-07-21 19:05         ` Palmer Dabbelt
2020-07-21 23:12           ` Benjamin Herrenschmidt
2020-07-21 23:48             ` Palmer Dabbelt
2020-07-22  2:21               ` Benjamin Herrenschmidt
2020-07-22  4:50                 ` Michael Ellerman
2020-07-22  5:46                   ` Palmer Dabbelt
2020-07-22  9:43           ` Arnd Bergmann
2020-07-22 19:52             ` Palmer Dabbelt
2020-07-22 20:22               ` Arnd Bergmann
2020-07-22 21:05                 ` Atish Patra
2020-07-24  7:20                   ` Arnd Bergmann
2020-07-23  5:32           ` Alex Ghiti
2020-07-21 23:11         ` Benjamin Herrenschmidt
2020-07-21 23:36           ` Palmer Dabbelt
2020-07-23  5:36             ` Alex Ghiti
2020-07-23  5:21           ` Alex Ghiti
2020-07-23 22:33             ` Benjamin Herrenschmidt [this message]
2020-07-24  8:14               ` Arnd Bergmann
2020-06-07  7:59 ` [PATCH v5 2/4] riscv: Introduce CONFIG_RELOCATABLE Alexandre Ghiti
2020-06-10 14:10   ` Jerome Forissier
2020-06-11 19:43     ` Alex Ghiti
2020-06-07  7:59 ` [PATCH v5 3/4] powerpc: Move script to check relocations at compile time in scripts/ Alexandre Ghiti
2020-06-07  7:59 ` [PATCH v5 4/4] riscv: Check relocations at compile time Alexandre Ghiti
2020-07-08  4:21 ` [PATCH v5 0/4] vmalloc kernel mapping and relocatable kernel Alex Ghiti

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