x86/mtrr: Simplify mtrr_ops initialization

The way mtrr_if is initialized with the correct mtrr_ops structure is
quite weird.

Simplify that by dropping the vendor specific init functions and the
mtrr_ops[] array. Replace those with direct assignments of the related
vendor specific ops array to mtrr_if.

Note that a direct assignment is okay even for 64-bit builds, where the
symbol isn't present, as the related code will be subject to "dead code
elimination" due to how cpu_feature_enabled() is implemented.
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20221102074713.21493-17-jgross@suse.comSigned-off-by: Borislav Petkov <bp@suse.de>

arch/x86/kernel/cpu/mtrr/amd.c

@@ -109,7 +109,7 @@ amd_validate_add_page(unsigned long base, unsigned long size, unsigned int type)
 	return 0;
 }
 
-static const struct mtrr_ops amd_mtrr_ops = {
+const struct mtrr_ops amd_mtrr_ops = {
 	.vendor            = X86_VENDOR_AMD,
 	.set               = amd_set_mtrr,
 	.get               = amd_get_mtrr,
@@ -117,9 +117,3 @@ static const struct mtrr_ops amd_mtrr_ops = {
 	.validate_add_page = amd_validate_add_page,
 	.have_wrcomb       = positive_have_wrcomb,
 };
-
-int __init amd_init_mtrr(void)
-{
-	set_mtrr_ops(&amd_mtrr_ops);
-	return 0;
-}

arch/x86/kernel/cpu/mtrr/centaur.c

@@ -111,7 +111,7 @@ centaur_validate_add_page(unsigned long base, unsigned long size, unsigned int t
 	return 0;
 }
 
-static const struct mtrr_ops centaur_mtrr_ops = {
+const struct mtrr_ops centaur_mtrr_ops = {
 	.vendor            = X86_VENDOR_CENTAUR,
 	.set               = centaur_set_mcr,
 	.get               = centaur_get_mcr,
@@ -119,9 +119,3 @@ static const struct mtrr_ops centaur_mtrr_ops = {
 	.validate_add_page = centaur_validate_add_page,
 	.have_wrcomb       = positive_have_wrcomb,
 };
-
-int __init centaur_init_mtrr(void)
-{
-	set_mtrr_ops(&centaur_mtrr_ops);
-	return 0;
-}

arch/x86/kernel/cpu/mtrr/cyrix.c

@@ -234,7 +234,7 @@ static void cyrix_set_arr(unsigned int reg, unsigned long base,
 	post_set();
 }
 
-static const struct mtrr_ops cyrix_mtrr_ops = {
+const struct mtrr_ops cyrix_mtrr_ops = {
 	.vendor            = X86_VENDOR_CYRIX,
 	.set               = cyrix_set_arr,
 	.get               = cyrix_get_arr,
@@ -242,9 +242,3 @@ static const struct mtrr_ops cyrix_mtrr_ops = {
 	.validate_add_page = generic_validate_add_page,
 	.have_wrcomb       = positive_have_wrcomb,
 };
-
-int __init cyrix_init_mtrr(void)
-{
-	set_mtrr_ops(&cyrix_mtrr_ops);
-	return 0;
-}

arch/x86/kernel/cpu/mtrr/mtrr.c

@@ -69,16 +69,8 @@ static DEFINE_MUTEX(mtrr_mutex);
 
 u64 size_or_mask, size_and_mask;
 
-static const struct mtrr_ops *mtrr_ops[X86_VENDOR_NUM] __ro_after_init;
-
 const struct mtrr_ops *mtrr_if;
 
-void __init set_mtrr_ops(const struct mtrr_ops *ops)
-{
-	if (ops->vendor && ops->vendor < X86_VENDOR_NUM)
-		mtrr_ops[ops->vendor] = ops;
-}
-
 /*  Returns non-zero if we have the write-combining memory type  */
 static int have_wrcomb(void)
 {
@@ -582,20 +574,6 @@ int arch_phys_wc_index(int handle)
 }
 EXPORT_SYMBOL_GPL(arch_phys_wc_index);
 
-/*
- * HACK ALERT!
- * These should be called implicitly, but we can't yet until all the initcall
- * stuff is done...
- */
-static void __init init_ifs(void)
-{
-#ifndef CONFIG_X86_64
-	amd_init_mtrr();
-	cyrix_init_mtrr();
-	centaur_init_mtrr();
-#endif
-}
-
 /* The suspend/resume methods are only for CPU without MTRR. CPU using generic
  * MTRR driver doesn't require this
  */
@@ -653,8 +631,6 @@ void __init mtrr_bp_init(void)
 {
 	u32 phys_addr;
 
-	init_ifs();
-
 	phys_addr = 32;
 
 	if (boot_cpu_has(X86_FEATURE_MTRR)) {
@@ -695,21 +671,21 @@ void __init mtrr_bp_init(void)
 		case X86_VENDOR_AMD:
 			if (cpu_feature_enabled(X86_FEATURE_K6_MTRR)) {
 				/* Pre-Athlon (K6) AMD CPU MTRRs */
-				mtrr_if = mtrr_ops[X86_VENDOR_AMD];
+				mtrr_if = &amd_mtrr_ops;
 				size_or_mask = SIZE_OR_MASK_BITS(32);
 				size_and_mask = 0;
 			}
 			break;
 		case X86_VENDOR_CENTAUR:
 			if (cpu_feature_enabled(X86_FEATURE_CENTAUR_MCR)) {
-				mtrr_if = mtrr_ops[X86_VENDOR_CENTAUR];
+				mtrr_if = &centaur_mtrr_ops;
 				size_or_mask = SIZE_OR_MASK_BITS(32);
 				size_and_mask = 0;
 			}
 			break;
 		case X86_VENDOR_CYRIX:
 			if (cpu_feature_enabled(X86_FEATURE_CYRIX_ARR)) {
-				mtrr_if = mtrr_ops[X86_VENDOR_CYRIX];
+				mtrr_if = &cyrix_mtrr_ops;
 				size_or_mask = SIZE_OR_MASK_BITS(32);
 				size_and_mask = 0;
 			}

arch/x86/kernel/cpu/mtrr/mtrr.h

@@ -51,8 +51,6 @@ void fill_mtrr_var_range(unsigned int index,
 		u32 base_lo, u32 base_hi, u32 mask_lo, u32 mask_hi);
 bool get_mtrr_state(void);
 
-extern void __init set_mtrr_ops(const struct mtrr_ops *ops);
-
 extern u64 size_or_mask, size_and_mask;
 extern const struct mtrr_ops *mtrr_if;
 
@@ -66,10 +64,10 @@ void mtrr_state_warn(void);
 const char *mtrr_attrib_to_str(int x);
 void mtrr_wrmsr(unsigned, unsigned, unsigned);
 
-/* CPU specific mtrr init functions */
-int amd_init_mtrr(void);
-int cyrix_init_mtrr(void);
-int centaur_init_mtrr(void);
+/* CPU specific mtrr_ops vectors. */
+extern const struct mtrr_ops amd_mtrr_ops;
+extern const struct mtrr_ops cyrix_mtrr_ops;
+extern const struct mtrr_ops centaur_mtrr_ops;
 
 extern int changed_by_mtrr_cleanup;
 extern int mtrr_cleanup(unsigned address_bits);