linux-kernel - Re: [PATCH v5 3/7] x86/microcode/intel: Establish staging control logic

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Message-ID: <20250905111349.GAaLrF7eWikC8BpiDK@fat_crate.local>
Date: Fri, 5 Sep 2025 13:13:49 +0200
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, chao.gao@...el.com,
	abusse@...zon.de
Subject: Re: [PATCH v5 3/7] x86/microcode/intel: Establish staging control
 logic

On Thu, Sep 04, 2025 at 05:04:24PM -0700, Chang S. Bae wrote:
> Okay, I think this 'MCU' looks a bit fuzzy. 

I mean we should try to sort them by MSR *number* so that they're easier to
find. I know, I know, the whole file needs sorting but we don't need the churn
right now. So let's put new ones where they should be, i.e.:

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 6eb0c62c7fbd..87be1f815211 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -922,8 +922,6 @@
 #define MSR_IA32_UCODE_WRITE		0x00000079
 #define MSR_IA32_UCODE_REV		0x0000008b
 
-#define MSR_IA32_MCU_STAGING_MBOX_ADDR	0x000007a5
-
 /* Intel SGX Launch Enclave Public Key Hash MSRs */
 #define MSR_IA32_SGXLEPUBKEYHASH0	0x0000008C
 #define MSR_IA32_SGXLEPUBKEYHASH1	0x0000008D
@@ -1219,6 +1217,8 @@
 #define MSR_IA32_VMX_VMFUNC             0x00000491
 #define MSR_IA32_VMX_PROCBASED_CTLS3	0x00000492
 
+#define MSR_IA32_MCU_STAGING_MBOX_ADDR	0x000007a5
+
 /* Resctrl MSRs: */
 /* - Intel: */
 #define MSR_IA32_L3_QOS_CFG		0xc81

> The next two patches in this series introduce helpers that return an error
> code and *also* update this ucode_state. The latter could go away. Instead,
> the error code could be just down through here and decoded like:

You don't need the strings decoding... yet. This stuff is going to be looked
at only by us so there's no problem with simply dumping the errval and then
going to consult the sources where that value comes from.

Thx.

-- 
Regards/Gruss,
    Boris.

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