linux-kernel - [PATCH v6 09/16] x86/mtrr: allocate mtrr

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Message-Id: <20230502120931.20719-10-jgross@suse.com>
Date:   Tue,  2 May 2023 14:09:24 +0200
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     mikelley@...rosoft.com, Juergen Gross <jgross@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH v6 09/16] x86/mtrr: allocate mtrr_value array dynamically

The mtrr_value[] array is a static variable, which is used only in a
few configurations. Consuming 6kB is ridiculous for this case,
especially as the array doesn't need to be that large and it can easily
be allocated dynamically.

Signed-off-by: Juergen Gross <jgross@...e.com>
Tested-by: Michael Kelley <mikelley@...rosoft.com>
---
V5:
- check for allocation failure (Kai Huang, Boris Petkov)
- add #ifdef
V6:
- rebase
---
 arch/x86/kernel/cpu/mtrr/legacy.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mtrr/legacy.c b/arch/x86/kernel/cpu/mtrr/legacy.c
index 7d379fb26cce..d25882fcf181 100644
--- a/arch/x86/kernel/cpu/mtrr/legacy.c
+++ b/arch/x86/kernel/cpu/mtrr/legacy.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-only
 
 #include <linux/types.h>
+#include <linux/slab.h>
 #include <linux/syscore_ops.h>
 #include <asm/cpufeature.h>
 #include <asm/mtrr.h>
@@ -38,12 +39,15 @@ struct mtrr_value {
 	unsigned long	lsize;
 };
 
-static struct mtrr_value mtrr_value[MTRR_MAX_VAR_RANGES];
+static struct mtrr_value *mtrr_value;
 
 static int mtrr_save(void)
 {
 	int i;
 
+	if (!mtrr_value)
+		return -ENOMEM;
+
 	for (i = 0; i < num_var_ranges; i++) {
 		mtrr_if->get(i, &mtrr_value[i].lbase,
 				&mtrr_value[i].lsize,
@@ -72,6 +76,8 @@ static struct syscore_ops mtrr_syscore_ops = {
 
 void mtrr_register_syscore(void)
 {
+	mtrr_value = kcalloc(num_var_ranges, sizeof(*mtrr_value), GFP_KERNEL);
+
 	/*
 	 * The CPU has no MTRR and seems to not support SMP. They have
 	 * specific drivers, we use a tricky method to support
-- 
2.35.3