Messages in this thread | | | Date | Wed, 20 Jul 2016 20:02:56 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86, fpu: do not BUG_ON() in early FPU code |
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* Dave Hansen <dave@sr71.net> wrote:
> > From: Dave Hansen <dave.hansen@linux.intel.com> > > I don't think it is really possible to have a system where CPUID > enumerates support for XSAVE but that it does not have FP/SSE > (they are "legacy" features and always present). > > But, I did manage to hit this case in qemu when I enabled its > somewhat shaky XSAVE support. The bummer is that the FPU is set > up before we parse the command-line or have *any* console support > including earlyprintk. > > So a BUG() here is worthless. All it does it guarantee that > if/when we hit this case we have an empty console. So, remove > the BUG() and try to limp along by disabling XSAVE and trying to > continue. > > Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> > --- > > b/arch/x86/kernel/fpu/xstate.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff -puN arch/x86/kernel/fpu/xstate.c~x86-fpu-do-not-BUG_ON-early arch/x86/kernel/fpu/xstate.c > --- a/arch/x86/kernel/fpu/xstate.c~x86-fpu-do-not-BUG_ON-early 2016-07-20 09:03:07.347941392 -0700 > +++ b/arch/x86/kernel/fpu/xstate.c 2016-07-20 09:17:15.001309137 -0700 > @@ -715,7 +715,8 @@ void __init fpu__init_system_xstate(void > > if ((xfeatures_mask & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) { > pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask); > - BUG(); > + fpu__init_disable_system_xstate(); > + return;
Ok, but please put a comment there explaining why we are not stopping the system.
Thanks,
Ingo
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