linux-kernel - [v2 PATCH] x86/microcode: Do not select FW

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Message-ID: <20200610110513.GA22897@gondor.apana.org.au>
Date:   Wed, 10 Jun 2020 21:05:13 +1000
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        x86-ml <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>
Subject: [v2 PATCH] x86/microcode: Do not select FW_LOADER

On Wed, Jun 10, 2020 at 12:48:45PM +0200, Borislav Petkov wrote:
>
> Why isn't *this* in your commit message?

Sure, here it is.

---8<---
The x86 microcode support works just fine without FW_LOADER.  In
fact these days most people load them early in boot so FW_LOADER
never gets into the picture anyway.

As almost everyone on x86 needs to enable MICROCODE this by extension
means that FW_LOADER is always built into the kernel even if nothing
uses it.  The FW_LOADER system is about two thousand lines long and
contains user-space facing interfaces that could potentially provide
an entry point into the kernel (or beyond).

This patch removes the unnecessary select of FW_LOADER by MICROCODE.
People who need the FW_LOADER capability can still enable it.

Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 1d6104ea8af0..8aac7a65bfbb 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1296,7 +1296,6 @@ config MICROCODE
 	bool "CPU microcode loading support"
 	default y
 	depends on CPU_SUP_AMD || CPU_SUP_INTEL
-	select FW_LOADER
 	---help---
 	  If you say Y here, you will be able to update the microcode on
 	  Intel and AMD processors. The Intel support is for the IA32 family,
@@ -1318,7 +1317,6 @@ config MICROCODE_INTEL
 	bool "Intel microcode loading support"
 	depends on MICROCODE
 	default MICROCODE
-	select FW_LOADER
 	---help---
 	  This options enables microcode patch loading support for Intel
 	  processors.
@@ -1330,7 +1328,6 @@ config MICROCODE_INTEL
 config MICROCODE_AMD
 	bool "AMD microcode loading support"
 	depends on MICROCODE
-	select FW_LOADER
 	---help---
 	  If you select this option, microcode patch loading support for AMD
 	  processors will be enabled.
diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 7019d4b2df0c..5524ea15b3df 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -145,7 +145,6 @@ extern struct builtin_fw __end_builtin_fw[];
 
 bool get_builtin_firmware(struct cpio_data *cd, const char *name)
 {
-#ifdef CONFIG_FW_LOADER
 	struct builtin_fw *b_fw;
 
 	for (b_fw = __start_builtin_fw; b_fw != __end_builtin_fw; b_fw++) {
@@ -155,7 +154,6 @@ bool get_builtin_firmware(struct cpio_data *cd, const char *name)
 			return true;
 		}
 	}
-#endif
 	return false;
 }
 
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt