Date: Wed, 16 Aug 2017 08:01:03 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 219399] System panics after several hours of 14-threads-compilation orgies using poudriere on AMD Ryzen... Message-ID: <bug-219399-8-rnMWzaJ2Hu@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-219399-8@https.bugs.freebsd.org/bugzilla/> References: <bug-219399-8@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D219399 --- Comment #219 from commit-hook@freebsd.org --- A commit references this bug: Author: truckman Date: Wed Aug 16 07:59:58 UTC 2017 New revision: 322569 URL: https://svnweb.freebsd.org/changeset/base/322569 Log: MFC r321899 Lower the amd64 shared page, which contains the signal trampoline, from the top of user memory to one page lower on machines with the Ryzen (AMD Family 17h) CPU. This pushes ps_strings and the stack down by one page as well. On Ryzen there is some sort of interaction between code running at the top of user memory address space and interrupts that can cause FreeBSD to either hang or silently reset. This sounds similar to the problem found with DragonFly BSD that was fixed with this commit: =20=20=20 https://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/b48dd28447fc8ef62f= bc963accd301557fd9ac20 but our signal trampoline location was already lower than the address that DragonFly moved their signal trampoline to. It also does not appear to be related to SMT as described here: =20=20=20 https://www.phoronix.com/forums/forum/hardware/processors-memory/955368-som= e-ryzen-linux-users-are-facing-issues-with-heavy-compilation-loads?p=3D9554= 98#post955498 "Hi, Matt Dillon here. Yes, I did find what I believe to be a hardware issue with Ryzen related to concurrent operations. In a nutshell, for any given hyperthread pair, if one hyperthread is in a cpu-bound loop of any kind (can be in user mode), and the other hyperthread is returning from an interrupt via IRETQ, the hyperthread issuing the IRETQ can stall indefinitely until the other hyperthread with the cpu-bound loop pauses (aka HLT until next interrupt). After this situation occurs, the system appears to destabilize. The situation does not occur if the cpu-bound loop is on a different core than the core doing the IRETQ. The %rip the IRETQ returns to (e.g. userland %rip address) matters a *LOT*. The problem occurs more often with high %rip addresses such as near the top of the user stack, which is where DragonFly's signal trampoline traditionally resides. So a user program taking a signal on one thread while another thread is cpu-bound can cause this behavior. Changing the location of the signal trampoline makes it more difficult to reproduce the problem. I have not been because the able to completely mitigate it. When a cpu-thread stalls in this manner it appears to stall INSIDE the microcode for IRETQ. It doesn't make it to the return pc, and the cpu thread cannot take any IPIs or other hardware interrupts while in this state." since the system instability has been observed on FreeBSD with SMT disabled. Interrupts to appear to play a factor since running a signal-intensive process on the first CPU core, which handles most of the interrupts on my machine, is far more likely to trigger the problem than running such a process on any other core. Also lower sv_maxuser to prevent a malicious user from using mmap() to load and execute code in the top page of user memory that was made available when the shared page was moved down. Make the same changes to the 64-bit Linux emulator. PR: 219399 Reported by: nbe@renzel.net Reviewed by: kib Reviewed by: dchagin (previous version) Tested by: nbe@renzel.net (earlier version) Differential Revision: https://reviews.freebsd.org/D11780 Changes: _U stable/11/ stable/11/sys/amd64/amd64/elf_machdep.c stable/11/sys/amd64/amd64/initcpu.c stable/11/sys/amd64/include/md_var.h stable/11/sys/amd64/linux/linux_sysvec.c --=20 You are receiving this mail because: You are the assignee for the bug.=
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