diff options
| author | Sebastian Andrzej Siewior <[email protected]> | 2018-10-16 22:25:25 +0200 |
|---|---|---|
| committer | Ingo Molnar <[email protected]> | 2018-10-17 12:30:38 +0200 |
| commit | 2224d616528194b02424c91c2ee254b3d29942c3 (patch) | |
| tree | 6598026698d14cee35e22bbc3c9ff0f902269d6a | |
| parent | 6aa676761d4c1acfa31320e55fa1f83f3fcbbc7a (diff) | |
x86/fpu: Fix i486 + no387 boot crash by only saving FPU registers on context switch if there is an FPU
Booting an i486 with "no387 nofxsr" ends with with the following crash:
math_emulate: 0060:c101987d
Kernel panic - not syncing: Math emulation needed in kernel
on the first context switch in user land.
The reason is that copy_fpregs_to_fpstate() tries FNSAVE which does not work
as the FPU is turned off.
This bug was introduced in:
f1c8cd0176078 ("x86/fpu: Change fpu->fpregs_active users to fpu->fpstate_active")
Add a check for X86_FEATURE_FPU before trying to save FPU registers (we
have such a check in switch_fpu_finish() already).
Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
Reviewed-by: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Fixes: f1c8cd0176078 ("x86/fpu: Change fpu->fpregs_active users to fpu->fpstate_active")
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
| -rw-r--r-- | arch/x86/include/asm/fpu/internal.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index a38bf5a1e37a..69dcdf195b61 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -528,7 +528,7 @@ static inline void fpregs_activate(struct fpu *fpu) static inline void switch_fpu_prepare(struct fpu *old_fpu, int cpu) { - if (old_fpu->initialized) { + if (static_cpu_has(X86_FEATURE_FPU) && old_fpu->initialized) { if (!copy_fpregs_to_fpstate(old_fpu)) old_fpu->last_cpu = -1; else |