Commit 6e686709 authored by Borislav Petkov's avatar Borislav Petkov Committed by Ingo Molnar

x86/fpu: Fix eager-FPU handling on legacy FPU machines

i486 derived cores like Intel Quark support only the very old,
legacy x87 FPU (FSAVE/FRSTOR, CPUID bit FXSR is not set), and
our FPU code wasn't handling the saving and restoring there
properly in the 'eagerfpu' case.

So after we made eagerfpu the default for all CPU types:

  58122bf1 x86/fpu: Default eagerfpu=on on all CPUs

these old FPU designs broke. First, Andy Shevchenko reported a splat:

  WARNING: CPU: 0 PID: 823 at arch/x86/include/asm/fpu/internal.h:163 fpu__clear+0x8c/0x160

which was us trying to execute FXRSTOR on those machines even though
they don't support it.

After taking care of that, Bryan O'Donoghue reported that a simple FPU
test still failed because we weren't initializing the FPU state properly
on those machines.

Take care of all that.
Reported-and-tested-by: default avatarBryan O'Donoghue <pure.logic@nexus-software.ie>
Reported-by: default avatarAndy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Acked-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yu-cheng <yu-cheng.yu@intel.com>
Link: http://lkml.kernel.org/r/20160311113206.GD4312@pd.tnicSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 84477336
...@@ -409,8 +409,10 @@ static inline void copy_init_fpstate_to_fpregs(void) ...@@ -409,8 +409,10 @@ static inline void copy_init_fpstate_to_fpregs(void)
{ {
if (use_xsave()) if (use_xsave())
copy_kernel_to_xregs(&init_fpstate.xsave, -1); copy_kernel_to_xregs(&init_fpstate.xsave, -1);
else else if (static_cpu_has(X86_FEATURE_FXSR))
copy_kernel_to_fxregs(&init_fpstate.fxsave); copy_kernel_to_fxregs(&init_fpstate.fxsave);
else
copy_kernel_to_fregs(&init_fpstate.fsave);
} }
/* /*
......
...@@ -134,7 +134,7 @@ static void __init fpu__init_system_generic(void) ...@@ -134,7 +134,7 @@ static void __init fpu__init_system_generic(void)
* Set up the legacy init FPU context. (xstate init might overwrite this * Set up the legacy init FPU context. (xstate init might overwrite this
* with a more modern format, if the CPU supports it.) * with a more modern format, if the CPU supports it.)
*/ */
fpstate_init_fxstate(&init_fpstate.fxsave); fpstate_init(&init_fpstate);
fpu__init_system_mxcsr(); fpu__init_system_mxcsr();
} }
......
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