From mboxrd@z Thu Jan 1 00:00:00 1970 From: alex.shi@linaro.org (Alex Shi) Date: Sat, 3 Mar 2018 08:54:10 +0800 Subject: [PATCH 00/45] arm Spectre fix backport review for LTS 4.9 In-Reply-To: <20180302103046.GC19323@arm.com> References: <1519908862-11425-1-git-send-email-alex.shi@linaro.org> <20180301164630.GB23321@kroah.com> <20180302103046.GC19323@arm.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 03/02/2018 06:30 PM, Will Deacon wrote: > On Fri, Mar 02, 2018 at 05:02:32PM +0800, Alex Shi wrote: >> As testing the spectre bug fix, that's a good question. I also asked >> this question to original patch authors, like Marc. They said they just >> figure out these patches could block spectre or meltdown issue. From my >> side, I just reproduced the process internal spectre. But all fix on arm >> can not resolve the user space internal spectre. It can block from user >> to kernel or kernel to user spectre according the code purose. So I >> believe these patch could do their job. And arm cpu would drop the >> spectre branches if it has 20+ 'nop' instructions... > > Since this is archived on a public list and I don't want people to rely on > this, no, you cannot rely on "20+ 'nop' instructions" to work around > spectre on arm/arm64. It might prevent a particular PoC working on a > particular SoC, but it's fragile at best. > Thanks for comments, Will! Yes, I full understand the difference between SoCs. Thanks for point it out! Regards Alex