[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAHp75VetABhKYverANgLwsHS+L6T8nxQqcbDGT8fwN8xrURJ6Q@mail.gmail.com>
Date: Thu, 10 Mar 2016 17:22:08 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Borislav Petkov <bp@...en8.de>
Cc: Ingo Molnar <mingo@...nel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"x86@...nel.org" <x86@...nel.org>,
Andy Lutomirski <luto@...capital.net>,
Fenghua Yu <fenghua.yu@...el.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
"H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Andrew Morton <akpm@...ux-foundation.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Oleg Nesterov <oleg@...hat.com>,
"Yu, Yu-cheng" <yu-cheng.yu@...el.com>
Subject: Re: Got FPU related warning on Intel Quark during boot
On Thu, Mar 10, 2016 at 4:59 PM, Borislav Petkov <bp@...en8.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.shevchenko@...il.com>
> }
>
> /*
--
With Best Regards,
Andy Shevchenko
Powered by blists - more mailing lists