linux-kernel - [PATCH v7 7/9] x86/microcode/AMD: Add a reminder about PATCH_MAX

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Date:   Tue, 19 Jun 2018 20:47:37 +0200
From:   "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v7 7/9] x86/microcode/AMD: Add a reminder about PATCH_MAX_SIZE macro

The PATCH_MAX_SIZE macro should contain the maximum of all family patch
sizes.
Since these sizes are defined in an other place than this macro, let's add
a reminder to them so people will remember to verify PATCH_MAX_SIZE
correctness when modifying a family patch size or adding a new family.

Signed-off-by: Maciej S. Szmigiero <mail@...iej.szmigiero.name>
---
 arch/x86/include/asm/microcode_amd.h | 1 +
 arch/x86/kernel/cpu/microcode/amd.c  | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/arch/x86/include/asm/microcode_amd.h b/arch/x86/include/asm/microcode_amd.h
index 209492849566..8ea477fbc65f 100644
--- a/arch/x86/include/asm/microcode_amd.h
+++ b/arch/x86/include/asm/microcode_amd.h
@@ -41,6 +41,7 @@ struct microcode_amd {
 	unsigned int			mpb[0];
 };
 
+/* Maximum patch size of all supported families */
 #define PATCH_MAX_SIZE PAGE_SIZE
 
 #ifdef CONFIG_MICROCODE_AMD
diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c
index 2dbdd7951475..9807e27f8fde 100644
--- a/arch/x86/kernel/cpu/microcode/amd.c
+++ b/arch/x86/kernel/cpu/microcode/amd.c
@@ -215,6 +215,9 @@ static bool verify_patch(u8 family, const u8 *buf, size_t buf_size,
 	/*
 	 * Check whether patch_size isn't something nonsensically huge so
 	 * we don't skip over good patches by mistake.
+	 *
+	 * If you modify these values or add a new one also check whether
+	 * PATCH_MAX_SIZE in include/asm/microcode_amd.h needs updating, too.
 	 */
 #define F1XH_MPB_MAX_SIZE 2048
 #define F14H_MPB_MAX_SIZE 1824