From: Nick Kossifidis <mick@ics.forth.gr>
To: Christoph Hellwig <hch@infradead.org>
Cc: mark.rutland@arm.com, steve@sk2.org, davidgow@google.com,
catalin.marinas@arm.com, linus.walleij@linaro.org,
Palmer Dabbelt <palmerdabbelt@google.com>,
elver@google.com, glider@google.com, willy@infradead.org,
zong.li@sifive.com, mchehab+samsung@kernel.org,
linux-riscv@lists.infradead.org, alex.shi@linux.alibaba.com,
will@kernel.org, ardb@kernel.org, linux-arch@vger.kernel.org,
Arnd Bergmann <arnd@arndb.de>,
alex@ghiti.fr, takahiro.akashi@linaro.org, masahiroy@kernel.org,
linux@armlinux.org.uk, krzk@kernel.org,
Mike Rapoport <rppt@linux.ibm.com>,
bgolaszewski@baylibre.com, Palmer Dabbelt <palmer@dabbelt.com>,
kernel-team@android.com, pmladek@suse.com,
zaslonko@linux.ibm.com, aou@eecs.berkeley.edu,
keescook@chromium.org, paulmck@kernel.org, rostedt@goodmis.org,
uwe@kleine-koenig.org, broonie@kernel.org,
matti.vaittinen@fi.rohmeurope.com, gregory.0xf0@gmail.com,
Paul Walmsley <paul.walmsley@sifive.com>,
dan.j.williams@intel.com, andriy.shevchenko@linux.intel.com,
gxt@pku.edu.cn, linux-arm-kernel@lists.infradead.org,
tglx@linutronix.de, rdunlap@infradead.org,
Nick Desaulniers <ndesaulniers@google.com>,
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james.morse@arm.com, mhiramat@kernel.org,
akpm@linux-foundation.org, davem@davemloft.net
Subject: Re: [PATCH 1/5] lib: Add a generic version of devmem_is_allowed()
Date: Fri, 10 Jul 2020 08:48:17 +0300 [thread overview]
Message-ID: <a037dac961c989d027eab293a0280643@mailhost.ics.forth.gr> (raw)
In-Reply-To: <20200710053850.GA27019@infradead.org>
Στις 2020-07-10 08:38, Christoph Hellwig έγραψε:
> On Thu, Jul 09, 2020 at 11:49:21PM +0300, Mike Rapoport wrote:
>> > +#ifndef CONFIG_GENERIC_DEVMEM_IS_ALLOWED
>> > +extern int devmem_is_allowed(unsigned long pfn);
>> > +#endif
>
> Nit: no need for the extern here.
>
>> > +config GENERIC_LIB_DEVMEM_IS_ALLOWED
>> > + bool
>> > + select ARCH_HAS_DEVMEM_IS_ALLOWED
>>
>> This seems to work the other way around from the usual Kconfig chains.
>> In the most cases ARCH_HAS_SOMETHING selects GENERIC_SOMETHING.
>>
>> I believe nicer way would be to make
>>
>> config STRICT_DEVMEM
>> bool "Filter access to /dev/mem"
>> depends on MMU && DEVMEM
>> depends on ARCH_HAS_DEVMEM_IS_ALLOWED ||
>> GENERIC_LIB_DEVMEM_IS_ALLOWED
>>
>> config GENERIC_LIB_DEVMEM_IS_ALLOWED
>> bool
>>
>> and then s/select ARCH_HAS_DEVMEM_IS_ALLOWED/select
>> GENERIC_LIB_DEVMEM_IS_ALLOWED/
>> in the arch Kconfigs and drop ARCH_HAS_DEVMEM_IS_ALLOWED in the end.
>
> To take a step back: Is there any reason to not just always
> STRICT_DEVMEM? Maybe for a few architectures that don't currently
> support a strict /dev/mem the generic version isn't quite correct, but
> someone selecting the option and finding the issue is the best way to
> figure that out..
>
During prototyping / testing having full access to all physical memory
through /dev/mem is very useful. We should have it enabled by default
but leave the config option there so that users / developers can disable
it if needed IMHO.
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next prev parent reply other threads:[~2020-07-10 5:56 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-09 20:05 Add and use a generic version of devmem_is_allowed() Palmer Dabbelt
2020-07-09 20:05 ` [PATCH 1/5] lib: Add " Palmer Dabbelt
2020-07-09 20:49 ` Mike Rapoport
2020-07-09 20:54 ` Palmer Dabbelt
2020-07-10 5:38 ` Christoph Hellwig
2020-07-10 5:48 ` Nick Kossifidis [this message]
2020-07-10 5:51 ` Christoph Hellwig
2020-07-09 20:05 ` [PATCH 2/5] RISC-V: Use the new generic devmem_is_allowed() Palmer Dabbelt
2020-07-09 20:05 ` [PATCH 3/5] arm: Use the " Palmer Dabbelt
2020-07-09 20:05 ` [PATCH 4/5] arm64: " Palmer Dabbelt
2020-07-09 20:05 ` [PATCH 5/5] unicore32: " Palmer Dabbelt
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