From: ashoks@broadcom•com (Ashok Kumar)
To: linux-arm-kernel@lists•infradead.org
Subject: [RFC PATCH 0/2] arm64: change PoC D-cache flush to PoU
Date: Mon, 14 Dec 2015 08:46:03 -0800 [thread overview]
Message-ID: <20151214164603.GA25971@ashoks@broadcom.com> (raw)
In-Reply-To: <20151214151117.GD22038@mbp>
Hi,
Thanks for the review.
On Mon, Dec 14, 2015 at 03:11:18PM +0000, Catalin Marinas wrote:
> On Mon, Dec 14, 2015 at 05:27:42AM -0800, Ashok Kumar wrote:
> > Also deferred dcache flush in __cpu_copy_user_page to __sync_icache_dcache.
> > May I know why I/D sync is needed in __cpu_copy_user_page? My understanding
> > is that any self modifying code in userspace is supposed to take care of the
> > coherency using the respective cache flush system call.
>
> I think it may have been there for historical reasons on arch/arm
> (115b22474eb1 - "ARM: 5794/1: Flush the D-cache during
> copy_user_highpage()") and imported in arch/arm64. But looking back at
> this, I don't think we need it for two reasons: dynamic linker no longer
> relocating symbols in a text page (and cause CoW) and set_pte_at()
> already calling __sync_icache_dcache().
In that case, shall we get rid of the flush in __sync_icache_dcache also
by not calling flush_dcache_page in __cpu_copy_user_page?
>
> --
> Catalin
>
next prev parent reply other threads:[~2015-12-14 16:46 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-14 13:27 [RFC PATCH 0/2] arm64: change PoC D-cache flush to PoU Ashok Kumar
2015-12-14 13:27 ` [RFC PATCH 1/2] arm64: Defer dcache flush in __cpu_copy_user_page Ashok Kumar
2015-12-14 15:18 ` Catalin Marinas
2015-12-14 13:27 ` [RFC PATCH 2/2] arm64: Use PoU cache instr for I/D coherency Ashok Kumar
2015-12-14 14:04 ` Mark Rutland
2015-12-14 16:48 ` Ashok Kumar
2015-12-14 15:11 ` [RFC PATCH 0/2] arm64: change PoC D-cache flush to PoU Catalin Marinas
2015-12-14 16:46 ` Ashok Kumar [this message]
2015-12-14 17:52 ` Catalin Marinas
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