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

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Date:   Mon, 15 Jun 2020 10:03:40 -0000
From:   "tip-bot2 for Herbert Xu" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        Borislav Petkov <bp@...e.de>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: x86/microcode] x86/microcode: Do not select FW_LOADER

The following commit has been merged into the x86/microcode branch of tip:

Commit-ID:     c8a59a4d8e3c9e609fa915e39c3628c6dd08aeea
Gitweb:        https://git.kernel.org/tip/c8a59a4d8e3c9e609fa915e39c3628c6dd08aeea
Author:        Herbert Xu <herbert@...dor.apana.org.au>
AuthorDate:    Wed, 10 Jun 2020 21:05:13 +10:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Mon, 15 Jun 2020 11:59:19 +02:00

x86/microcode: Do not select FW_LOADER

The x86 microcode support works just fine without FW_LOADER. In fact,
these days most people load microcode early during 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).

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

 [ bp: Massage a bit. ]

Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lkml.kernel.org/r/20200610042911.GA20058@gondor.apana.org.au
---
 arch/x86/Kconfig                     | 3 ---
 arch/x86/kernel/cpu/microcode/core.c | 2 --
 2 files changed, 5 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 6a0cc52..5c44eac 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1292,7 +1292,6 @@ 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,
@@ -1314,7 +1313,6 @@ 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.
@@ -1326,7 +1324,6 @@ 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 baec68b..ec6f041 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;
 }