From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Yury Norov <yury.norov@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Alexey Klimov <klimov.linux@gmail.com>,
Andy Shevchenko <andy.shevchenko@gmail.com>,
Andy Whitcroft <apw@canonical.com>,
Dennis Zhou <dennis@kernel.org>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Guenter Roeck <linux@roeck-us.net>,
Kees Cook <keescook@chromium.org>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>
Subject: Re: [PATCH 1/2] bitmap: add sanity check function for find_bit()
Date: Tue, 25 Oct 2022 19:26:20 +0100 [thread overview]
Message-ID: <Y1gqTM19oLeN59Kl@shell.armlinux.org.uk> (raw)
In-Reply-To: <Y1gY18JGz4zKw+gW@yury-laptop>
On Tue, Oct 25, 2022 at 10:11:51AM -0700, Yury Norov wrote:
> ARMv6 may or may not support unaligned access depending on SCTLR.U
> bit. This is what Russell was concerned about in the other email.
> As far as I understand, linux enables that feature.
However, we still support ARMv5 and ARMv4, both of which _trap_ every
unaligned access, which will make a findbit call with an unaligned
pointer using word loads painfully expensive. This is the main reason
we haven't used word loads in the findbit ops.
As mentioned, I have patches that do change that (and convert the
thing to use assembly macros to make updates much easier.)
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
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WARNING: multiple messages have this Message-ID (diff)
From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Yury Norov <yury.norov@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Alexey Klimov <klimov.linux@gmail.com>,
Andy Shevchenko <andy.shevchenko@gmail.com>,
Andy Whitcroft <apw@canonical.com>,
Dennis Zhou <dennis@kernel.org>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Guenter Roeck <linux@roeck-us.net>,
Kees Cook <keescook@chromium.org>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>
Subject: Re: [PATCH 1/2] bitmap: add sanity check function for find_bit()
Date: Tue, 25 Oct 2022 19:26:20 +0100 [thread overview]
Message-ID: <Y1gqTM19oLeN59Kl@shell.armlinux.org.uk> (raw)
In-Reply-To: <Y1gY18JGz4zKw+gW@yury-laptop>
On Tue, Oct 25, 2022 at 10:11:51AM -0700, Yury Norov wrote:
> ARMv6 may or may not support unaligned access depending on SCTLR.U
> bit. This is what Russell was concerned about in the other email.
> As far as I understand, linux enables that feature.
However, we still support ARMv5 and ARMv4, both of which _trap_ every
unaligned access, which will make a findbit call with an unaligned
pointer using word loads painfully expensive. This is the main reason
we haven't used word loads in the findbit ops.
As mentioned, I have patches that do change that (and convert the
thing to use assembly macros to make updates much easier.)
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
next prev parent reply other threads:[~2022-10-25 18:30 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-20 3:20 [RFC PATCH 0/2] Switch ARM to generic find_bit() API Yury Norov
2022-10-20 3:20 ` Yury Norov
2022-10-20 3:20 ` [PATCH 1/2] bitmap: add sanity check function for find_bit() Yury Norov
2022-10-20 3:20 ` Yury Norov
2022-10-23 22:19 ` Linus Torvalds
2022-10-23 22:19 ` Linus Torvalds
2022-10-25 17:11 ` Yury Norov
2022-10-25 17:11 ` Yury Norov
2022-10-25 18:26 ` Russell King (Oracle) [this message]
2022-10-25 18:26 ` Russell King (Oracle)
2022-10-25 18:38 ` Linus Torvalds
2022-10-25 18:38 ` Linus Torvalds
2022-11-14 11:59 ` Russell King (Oracle)
2022-11-14 11:59 ` Russell King (Oracle)
2022-10-20 3:20 ` [PATCH 2/2] arm: drop arch implementation for find_bit() functions Yury Norov
2022-10-20 3:20 ` Yury Norov
2022-10-20 16:51 ` [RFC PATCH 0/2] Switch ARM to generic find_bit() API Russell King (Oracle)
2022-10-20 16:51 ` Russell King (Oracle)
2022-10-20 20:02 ` Yury Norov
2022-10-20 20:02 ` Yury Norov
2022-10-20 22:55 ` Russell King (Oracle)
2022-10-20 22:55 ` Russell King (Oracle)
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