From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Matthew Wilcox <willy@infradead.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Kees Cook <keescook@chromium.org>,
Sri Krishna chowdary <schowdary@nvidia.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
x86@kernel.org, Dave Hansen <dave.hansen@intel.com>,
linux-kernel@vger.kernel.org, Steven Price <Steven.Price@arm.com>,
linux-mm@kvack.org, Mark Brown <Mark.Brown@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC] mm/pgtable/debug: Add test validating architecture page table helpers
Date: Thu, 25 Jul 2019 22:58:12 +0100 [thread overview]
Message-ID: <20190725215812.GN1330@shell.armlinux.org.uk> (raw)
In-Reply-To: <20190725214222.GG30641@bombadil.infradead.org>
On Thu, Jul 25, 2019 at 02:42:22PM -0700, Matthew Wilcox wrote:
> On Thu, Jul 25, 2019 at 10:38:58PM +0100, Russell King - ARM Linux admin wrote:
> > On Thu, Jul 25, 2019 at 07:39:21AM -0700, Matthew Wilcox wrote:
> > > But 'page' isn't necessarily PMD-aligned. I don't think we can rely on
> > > architectures doing the right thing if asked to make a PMD for a randomly
> > > aligned page.
> > >
> > > How about finding the physical address of something like kernel_init(),
> > > and using the corresponding pte/pmd/pud/p4d/pgd that encompasses that
> > > address? It's also better to pass in the pfn/page rather than using global
> > > variables to communicate to the test functions.
> >
> > There are architectures (32-bit ARM) where the kernel is mapped using
> > section mappings, and we don't expect the Linux page table walking to
> > work for section mappings.
>
> This test doesn't go so far as to insert the PTE/PMD/PUD/... into the
> page tables. It merely needs an appropriately aligned PFN to create a
> PTE/PMD/PUD/... from.
Well, in any case,
c085ac68 t kernel_init
so I'm not sure that would be an improvement.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
According to speedtest.net: 11.9Mbps down 500kbps up
WARNING: multiple messages have this Message-ID (diff)
From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Matthew Wilcox <willy@infradead.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
x86@kernel.org, Kees Cook <keescook@chromium.org>,
Sri Krishna chowdary <schowdary@nvidia.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Dave Hansen <dave.hansen@intel.com>,
linux-kernel@vger.kernel.org, Steven Price <Steven.Price@arm.com>,
linux-mm@kvack.org,
Masahiro Yamada <yamada.masahiro@socionext.com>,
Mark Brown <Mark.Brown@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC] mm/pgtable/debug: Add test validating architecture page table helpers
Date: Thu, 25 Jul 2019 22:58:12 +0100 [thread overview]
Message-ID: <20190725215812.GN1330@shell.armlinux.org.uk> (raw)
In-Reply-To: <20190725214222.GG30641@bombadil.infradead.org>
On Thu, Jul 25, 2019 at 02:42:22PM -0700, Matthew Wilcox wrote:
> On Thu, Jul 25, 2019 at 10:38:58PM +0100, Russell King - ARM Linux admin wrote:
> > On Thu, Jul 25, 2019 at 07:39:21AM -0700, Matthew Wilcox wrote:
> > > But 'page' isn't necessarily PMD-aligned. I don't think we can rely on
> > > architectures doing the right thing if asked to make a PMD for a randomly
> > > aligned page.
> > >
> > > How about finding the physical address of something like kernel_init(),
> > > and using the corresponding pte/pmd/pud/p4d/pgd that encompasses that
> > > address? It's also better to pass in the pfn/page rather than using global
> > > variables to communicate to the test functions.
> >
> > There are architectures (32-bit ARM) where the kernel is mapped using
> > section mappings, and we don't expect the Linux page table walking to
> > work for section mappings.
>
> This test doesn't go so far as to insert the PTE/PMD/PUD/... into the
> page tables. It merely needs an appropriately aligned PFN to create a
> PTE/PMD/PUD/... from.
Well, in any case,
c085ac68 t kernel_init
so I'm not sure that would be an improvement.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
According to speedtest.net: 11.9Mbps down 500kbps up
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next prev parent reply other threads:[~2019-07-25 21:58 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-25 6:55 [RFC] mm/debug: Add tests for architecture exported page table helpers Anshuman Khandual
2019-07-25 6:55 ` Anshuman Khandual
2019-07-25 6:55 ` [RFC] mm/pgtable/debug: Add test validating architecture " Anshuman Khandual
2019-07-25 6:55 ` Anshuman Khandual
2019-07-25 14:39 ` Matthew Wilcox
2019-07-25 14:39 ` Matthew Wilcox
2019-07-25 21:38 ` Russell King - ARM Linux admin
2019-07-25 21:38 ` Russell King - ARM Linux admin
2019-07-25 21:42 ` Matthew Wilcox
2019-07-25 21:42 ` Matthew Wilcox
2019-07-25 21:58 ` Russell King - ARM Linux admin [this message]
2019-07-25 21:58 ` Russell King - ARM Linux admin
2019-07-25 22:56 ` Matthew Wilcox
2019-07-25 22:56 ` Matthew Wilcox
2019-07-26 4:47 ` Anshuman Khandual
2019-07-26 4:47 ` Anshuman Khandual
2019-07-26 19:54 ` Matthew Wilcox
2019-07-26 19:54 ` Matthew Wilcox
2019-07-29 8:32 ` Anshuman Khandual
2019-07-29 8:32 ` Anshuman Khandual
2019-07-30 17:03 ` Matthew Wilcox
2019-07-30 17:03 ` Matthew Wilcox
2019-08-05 4:35 ` Anshuman Khandual
2019-08-05 4:35 ` Anshuman Khandual
2019-07-25 17:07 ` Catalin Marinas
2019-07-25 17:07 ` Catalin Marinas
2019-07-26 4:28 ` Anshuman Khandual
2019-07-26 4:28 ` Anshuman Khandual
2019-07-25 21:54 ` Russell King - ARM Linux admin
2019-07-25 21:54 ` Russell King - ARM Linux admin
2019-07-26 5:10 ` Anshuman Khandual
2019-07-26 5:10 ` Anshuman Khandual
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