linux-kernel - Re: [PATCH 3/6] x86/microcode/intel: Prepare for microcode staging

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Message-ID: <20250226175209.GNZ79UyXn5pODSYNrn@fat_crate.local>
Date: Wed, 26 Feb 2025 18:52:09 +0100
From: Borislav Petkov <bp@...en8.de>
To: "Chang S. Bae" <chang.seok.bae@...el.com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org, tglx@...utronix.de,
	mingo@...hat.com, dave.hansen@...ux.intel.com
Subject: Re: [PATCH 3/6] x86/microcode/intel: Prepare for microcode staging

On Tue, Dec 10, 2024 at 05:42:09PM -0800, Chang S. Bae wrote:
> +static void stage_microcode(void)
> +{
> +	unsigned int totalsize, pkg_id = UINT_MAX;
> +	enum ucode_state state;
> +	int cpu;
> +	u64 pa;
> +
> +	totalsize = get_totalsize(&ucode_patch_late->hdr);
> +	if (!IS_ALIGNED(totalsize, sizeof(u32)))
> +		return;


	... lockdep assert hotplug lock held blabla...

> +
> +	/*
> +	 * The MMIO address is unique per package, and all the SMT
> +	 * primary threads are online here. Find each MMIO space by
> +	 * their package ids to avoid duplicate staging.
> +	 */
> +	for_each_cpu(cpu, cpu_online_mask) {
> +		if (!topology_is_primary_thread(cpu) || topology_logical_package_id(cpu) == pkg_id)
> +			continue;

		if (!topology_is_primary_thread(cpu) ||
		     topology_logical_package_id(cpu) == pkg_id)


> +		pkg_id = topology_logical_package_id(cpu);
> +
> +		rdmsrl_on_cpu(cpu, MSR_IA32_MCU_STAGING_MBOX_ADDR, &pa);
> +
> +		state = do_stage(pa, ucode_patch_late, totalsize);
> +		if (state != UCODE_OK) {
> +			pr_err("Error: staging failed with %s for CPU%d at package %u.\n",
> +			       state == UCODE_TIMEOUT ? "timeout" : "error state", cpu, pkg_id);
> +			return;
> +		}
> +	}
> +
> +	pr_info("Staging of patch revision 0x%x succeeded.\n",
> +		((struct microcode_header_intel *)ucode_patch_late)->rev);
> +}
> +
>  static enum ucode_state __apply_microcode(struct ucode_cpu_info *uci,
>  					  struct microcode_intel *mc,
>  					  u32 *cur_rev)
> @@ -627,6 +662,7 @@ static struct microcode_ops microcode_intel_ops = {
>  	.collect_cpu_info	= collect_cpu_info,
>  	.apply_microcode	= apply_microcode_late,
>  	.finalize_late_load	= finalize_late_load,
> +	.stage_microcode	= stage_microcode,

Btw, you can get rid of ->use_staging and simply check whether
->stage_microcode is not NULL.

>  	.use_nmi		= IS_ENABLED(CONFIG_X86_64),
>  };
>  
> diff --git a/arch/x86/kernel/cpu/microcode/internal.h b/arch/x86/kernel/cpu/microcode/internal.h
> index b27cb8e1228d..158429d80f93 100644
> --- a/arch/x86/kernel/cpu/microcode/internal.h
> +++ b/arch/x86/kernel/cpu/microcode/internal.h
> @@ -120,11 +120,18 @@ void load_ucode_intel_bsp(struct early_load_data *ed);
>  void load_ucode_intel_ap(void);
>  void reload_ucode_intel(void);
>  struct microcode_ops *init_intel_microcode(void);
> +static inline enum ucode_state do_stage(u64 pa, void *ucode_ptr, unsigned int totalsize)
> +{
> +	pr_debug_once("Need to implement the staging code.\n");
> +	return UCODE_ERROR;
> +}
>  #else /* CONFIG_CPU_SUP_INTEL */
>  static inline void load_ucode_intel_bsp(struct early_load_data *ed) { }
>  static inline void load_ucode_intel_ap(void) { }
>  static inline void reload_ucode_intel(void) { }
>  static inline struct microcode_ops *init_intel_microcode(void) { return NULL; }
> +static inline enum ucode_state
> +do_stage(u64 pa, void *ucode_ptr, unsigned int totalsize) { return UCODE_ERROR; }
>  #endif  /* !CONFIG_CPU_SUP_INTEL */
>
You don't need to export those if staging is going to be done only by the
Intel side. Just keep everything in intel.c

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette