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Re: [PATCH v4 4/4] x86/microcode: Disable microcode update handler if DIS_MCU_UPDATE is set
- To: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Fri, 23 Jun 2023 09:39:35 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Fri, 23 Jun 2023 07:40:01 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 22.06.2023 19:42, Alejandro Vallejo wrote:
> --- a/xen/arch/x86/cpu/microcode/intel.c
> +++ b/xen/arch/x86/cpu/microcode/intel.c
> @@ -385,6 +385,19 @@ static struct microcode_patch *cf_check
> cpu_request_microcode(
> return patch;
> }
>
> +bool __init intel_can_load_microcode(void)
> +{
> + uint64_t mcu_ctrl;
> +
> + if ( !cpu_has_mcu_ctrl )
> + return true;
> +
> + rdmsrl(MSR_MCU_CONTROL, mcu_ctrl);
> +
> + /* If DIS_MCU_LOAD is set applying microcode updates won't work */
> + return !(mcu_ctrl & MCU_CONTROL_DIS_MCU_LOAD);
And we have to honor this, i.e. we shouldn't make an attempt
at clearing the bit?
Also nit: One too many blank after "return".
> --- a/xen/arch/x86/cpu/microcode/private.h
> +++ b/xen/arch/x86/cpu/microcode/private.h
> @@ -60,6 +60,13 @@ struct microcode_ops {
> const struct microcode_patch *new, const struct microcode_patch
> *old);
> };
>
> +/**
> + * Checks whether we can perform microcode updates on this Intel system
> + *
> + * @return True iff the microcode update facilities are enabled
> + */
> +bool __init intel_can_load_microcode(void);
No __init please on declarations; they only matter on definitions.
Jan
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