> On Sun, Jan 14, 2018 at 11:40 AM, Jan Hubicka <hubi...@ucw.cz> wrote: > >> Hi HJ, > >> > >> > -----Original Message----- > >> > From: gcc-patches-ow...@gcc.gnu.org [mailto:gcc-patches- > >> > ow...@gcc.gnu.org] On Behalf Of H.J. Lu > >> > Sent: Sunday, January 14, 2018 9:07 AM > >> > To: gcc-patches@gcc.gnu.org > >> > Subject: [PATCH 0/5] x86: CVE-2017-5715, aka Spectre > >> > > >> > This set of patches for GCC 8 mitigates variant #2 of the speculative > >> > execution vulnerabilities on x86 processors identified by CVE-2017-5715, > >> > aka > >> > Spectre. They convert indirect branches and function returns to call and > >> > return thunks to avoid speculative execution via indirect call, jmp and > >> > ret. > >> > > >> > H.J. Lu (5): > >> > x86: Add -mindirect-branch= > >> > x86: Add -mfunction-return= > >> > x86: Add -mindirect-branch-register > >> > x86: Add 'V' register operand modifier > >> > x86: Disallow -mindirect-branch=/-mfunction-return= with > >> > -mcmodel=large > >> > >> Current set of patches don't seem to have any option to generate "lfence" > >> as the loop filler in "retpoline", which is required by AMD. > >> Can you please clarify the plan. We would like to get this checked-in GCC > >> 8. > > > > Since thunks are output as strings, it is easy to add the option > > on the top of patch #1 of the series. I do not fully understand > > the reason for choosing pause over lfence for Intel, but if we need > > to do both, we need to have command line option (and possibly attribute). > > What would be reasonable name for it? > > Looking at the kernel patch [1], the loop filler should be > "pause;lfence" sequence, and should be universally accepted for Intel > and AMD targets. > > [1] https://www.spinics.net/lists/kernel/msg2697507.html
Yep, I would say we should go with pause;lfence now and see if we want to add argument eventually. HJ, does it sound OK? Honza > > Uros.
