On Thu, Mar 10, 2016 at 4:59 PM, Borislav Petkov <b...@alien8.de> wrote:
> On Thu, Mar 10, 2016 at 03:31:43PM +0200, Andy Shevchenko wrote:
>> Looks like it lacks that one.
>>
>> # grep -i fxsr /proc/cpuinfo; echo $?
>> 1
>
> Ok, so looking at where the warning comes from:
>
> [ 14.714533] WARNING: CPU: 0 PID: 823 at
> arch/x86/include/asm/fpu/internal.h:163 fpu__clear+0x8c/0x160
>
> static inline void copy_kernel_to_fxregs(struct fxregs_state *fx)
> {
> int err;
>
> if (config_enabled(CONFIG_X86_32)) {
> err = check_insn(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx));
> ^^^^^^^^^^^^^^^^^
> } else {
>
> ...
>
> /* Copying from a kernel buffer to FPU registers should never fail: */
> WARN_ON_FPU(err);
>
>
> and the stacktrace is pretty clear:
>
> flush_thread
> |-> fpu__clear(&tsk->thread.fpu);
> |-> we are eager by default here:
>
> if (!use_eager_fpu() || !static_cpu_has(X86_FEATURE_FPU)) {
> /* FPU state will be reallocated lazily at the first use. */
> fpu__drop(fpu);
> } else {
>
> --> we're in that branch.
>
> copy_init_fpstate_to_fpregs();
> |-> copy_kernel_to_fxregs()
>
>
> I think we should use FRSTOR on quark, i.e., copy_kernel_to_fregs().
>
> Does this untested wild guess even work?
>
> ---
> diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
> index dea8e76d60c6..bbafe5e8a1a6 100644
> --- a/arch/x86/kernel/fpu/core.c
> +++ b/arch/x86/kernel/fpu/core.c
> @@ -474,8 +474,11 @@ static inline void copy_init_fpstate_to_fpregs(void)
> {
> if (use_xsave())
> copy_kernel_to_xregs(&init_fpstate.xsave, -1);
> - else
> + else if (static_cpu_has(X86_FEATURE_FXSR))
> copy_kernel_to_fxregs(&init_fpstate.fxsave);
> + else
> + copy_kernel_to_fregs(&init_fpstate.fsave);
> +
Obviously redundant line, otherwise it indeed works
Tested-by: Andy Shevchenko <andy.shevche...@gmail.com>
> }
>
> /*
--
With Best Regards,
Andy Shevchenko
