Re: [PATCH] x86, msr: fix rdmsrl_safe_on_cpu()

From: Borislav Petkov
Date: Wed Mar 28 2018 - 06:09:42 EST


On Tue, Mar 27, 2018 at 08:22:33PM -0700, Eric Dumazet wrote:
> When changing rdmsr_safe_on_cpu() to schedule, I missed that
> __rdmsr_safe_on_cpu() was also used by rdmsrl_safe_on_cpu()
>
> Lets make rdmsrl_safe_on_cpu() a wrapper instead of copy/pasting
> the code I added for the completion handling.
>
> Fixes: 07cde313b2d2 ("x86/msr: Allow rdmsr_safe_on_cpu() to schedule")
> Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
> Reported-by: kbuild test robot <fengguang.wu@xxxxxxxxx>
> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxxxx>
> ---
> arch/x86/lib/msr-smp.c | 11 ++++-------
> 1 file changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/lib/msr-smp.c b/arch/x86/lib/msr-smp.c
> index 761ba062afdaf7f7d0603ed94ed6cc3e46b37f76..fee8b9c0520c9954e3cf9093332e1a9b53009b8b 100644
> --- a/arch/x86/lib/msr-smp.c
> +++ b/arch/x86/lib/msr-smp.c
> @@ -225,16 +225,13 @@ EXPORT_SYMBOL(wrmsrl_safe_on_cpu);
>
> int rdmsrl_safe_on_cpu(unsigned int cpu, u32 msr_no, u64 *q)
> {
> + u32 low, high;
> int err;
> - struct msr_info rv;
>
> - memset(&rv, 0, sizeof(rv));
> + err = rdmsr_safe_on_cpu(cpu, msr_no, &low, &high);
> + *q = (u64)high << 32 | low;
>
> - rv.msr_no = msr_no;
> - err = smp_call_function_single(cpu, __rdmsr_safe_on_cpu, &rv, 1);
> - *q = rv.reg.q;
> -
> - return err ? err : rv.err;
> + return err;
> }
> EXPORT_SYMBOL(rdmsrl_safe_on_cpu);
>
> --

I guess now that the rdmsr* side does this, you probably should convert
the wrmsr* side as well.

Thx.

--
Regards/Gruss,
Boris.

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