linux-kernel - [PATCH v5 09/15] x86/mtrr: allocate mtrr

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Date:   Sat,  1 Apr 2023 08:36:46 +0200
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     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>,
        Michael Kelley <mikelley@...rosoft.com>
Subject: [PATCH v5 09/15] 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.

The "few configurations" are all 32-bit ones, so put the code inside a
CONFIG_X86_32 #ifdef.

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
---
 arch/x86/kernel/cpu/mtrr/mtrr.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/mtrr/mtrr.c b/arch/x86/kernel/cpu/mtrr/mtrr.c
index 4fa3d0f94f39..76f5b5e1128b 100644
--- a/arch/x86/kernel/cpu/mtrr/mtrr.c
+++ b/arch/x86/kernel/cpu/mtrr/mtrr.c
@@ -560,8 +560,10 @@ int arch_phys_wc_index(int handle)
 }
 EXPORT_SYMBOL_GPL(arch_phys_wc_index);
 
-/* The suspend/resume methods are only for CPU without MTRR. CPU using generic
- * MTRR driver doesn't require this
+#ifdef CONFIG_X86_32
+/*
+ * The suspend/resume methods are only for CPUs without MTRR. CPUs using generic
+ * MTRR driver don't require this.
  */
 struct mtrr_value {
 	mtrr_type	ltype;
@@ -569,12 +571,15 @@ 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,
@@ -596,12 +601,11 @@ static void mtrr_restore(void)
 	}
 }
 
-
-
 static struct syscore_ops mtrr_syscore_ops = {
 	.suspend	= mtrr_save,
 	.resume		= mtrr_restore,
 };
+#endif /* CONFIG_X86_32 */
 
 int __initdata changed_by_mtrr_cleanup;
 
@@ -730,15 +734,20 @@ static int __init mtrr_init_finialize(void)
 		return 0;
 	}
 
+#ifdef CONFIG_X86_32
+	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
-	 * suspend/resume for them.
+	 * suspend/resume for them. In case above allocation failed we can't
+	 * support suspend/resume (handled in mtrr_save()).
 	 *
 	 * TBD: is there any system with such CPU which supports
 	 * suspend/resume? If no, we should remove the code.
 	 */
 	register_syscore_ops(&mtrr_syscore_ops);
+#endif
 
 	return 0;
 }
-- 
2.35.3