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