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Date: Wed, 16 Mar 2022 08:34:04 -0700 From: Dave Hansen <dave.hansen@...el.com> To: linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, Peter Zijlstra <peterz@...radead.org> Subject: Re: system locks up with CONFIG_SLS=Y; 5.17.0-rc On 3/16/22 02:51, Jamie Heilman wrote: > I've been (somewhat unsuccessfully) trying to bisect a hard lock-up > of my workstation that occurs when I'm running 5.17 rc kernels a few > seconds after I start a kvm guest instance. There is no output to > any log, everything locks up completely, sysrq doesn't even work > anymore. As bisection progressed closer and closer to the branch > where straight-line-speculation mitigation was enabled, and as bisect > landing me between 9cdbeec40968 ("x86/entry_32: Fix segment exceptions") > and 3411506550b1 ("x86/csum: Rewrite/optimize csum_partial()") wasn't > resulting in clear results (my system definately starts Oopsing and > gets so hosed up that I'm forced to reboot, but it isn't quite as dire > as sysrq continues to function) I decided to just try a build with > CONFIG_SLS disabled, and it turns out that works just fine. Sooo... > > This system uses a Intel Core2 Duo E8400 processor. > working config (CONFIG_SLS=N) and dmesg at: > http://audible.transient.net/~jamie/k/sls.config-5.17.0-rc8 > http://audible.transient.net/~jamie/k/sls.dmesg > > (I don't think the dmesg of CONFIG_SLS=Y is really any different.) If you get really ambitious, you could try to see if any of the individual things that change based on the CONFIG_SLS #ifdef trigger this. Basically, turn off the config option and then go manually enabling each of the sites. The odd thing is that it isn't touching anything really KVM-specific. It probably influences some KVM-specific assembly, but it's hard to see how that might break anything. The worrying part is: ifdef CONFIG_SLS KBUILD_CFLAGS += -mharden-sls=all endif That's presumably a shiny, new compiler option, also known as a relatively lightly tested compiler option.
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