From mboxrd@z Thu Jan 1 00:00:00 1970 From: marc.zyngier@arm.com (Marc Zyngier) Date: Mon, 20 Apr 2015 10:42:23 +0100 Subject: [PATCH] arm64: kill flush_cache_all() In-Reply-To: <1429521875-16893-1-git-send-email-mark.rutland@arm.com> References: <1429521875-16893-1-git-send-email-mark.rutland@arm.com> Message-ID: <5534C9FF.2030703@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Mark, On 20/04/15 10:24, Mark Rutland wrote: > The documented semantics of flush_cache_all are not possible to provide > for arm64 (short of flushing the entire physical address space by VA), > and there are currently no users; KVM uses VA maintenance exclusively, > cpu_reset is never called, and the only two users outside of arch code > cannot be built for arm64. > > While cpu_soft_reset and related functions (which call flush_cache_all) > were thought to be useful for kexec, their current implementations only > serve to mask bugs. For correctness kexec will need to perform > maintenance by VA anyway to account for system caches, line migration, > and other subtleties of the cache architecture. As the extent of this > cache maintenance will be kexec-specific, it should probably live in the > kexec code. I assume you mean that kexec will perform VA maintenance as part of its private cpu_soft_reset implementation, not that it will reimplement flush by S/W as a private method... > This patch removes flush_cache_all, and related unused components, > preventing further abuse. Excellent. I'm pleased we're getting rid of this code which could only be (ab)used by broken code. Hopefully this will send a clear message that maintenance by VA is the only way we can *safely* deal with caches on arm64. > > Signed-off-by: Mark Rutland > Cc: AKASHI Takahiro > Cc: Ard Biesheuvel > Cc: Catalin Marinas > Cc: Geoff Levand > Cc: Lorenzo Pieralisi > Cc: Marc Zyngier > Cc: Will Deacon Acked-by: Marc Zyngier M. -- Jazz is not dead. It just smells funny...