linux-kernel - [RFC][PATCH 16/34] x86/cpu: Move physical address limit out of cpuinfo

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Date: Thu, 22 Feb 2024 10:39:48 -0800
From: Dave Hansen <dave.hansen@...ux.intel.com>
To: linux-kernel@...r.kernel.org
Cc: kirill.shutemov@...ux.intel.com,pbonzini@...hat.com,tglx@...utronix.de,x86@...nel.org,bp@...en8.de,Dave Hansen <dave.hansen@...ux.intel.com>
Subject: [RFC][PATCH 16/34] x86/cpu: Move physical address limit out of cpuinfo_x86


From: Dave Hansen <dave.hansen@...ux.intel.com>

There are no longer any direct references to cpuinfo_x86->x86_phys_bits.
The only remaining references are to 'boot_cpu_data' via the
x86_phys_bits() helper.

This means the farce that x86_phys_bits is per-cpu data can end.  Remove
it from cpuinfo_x86 and add it to a new global data structure:
'x86_config'.  (Better names welcome)

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
---

 b/arch/x86/include/asm/processor.h |   16 ++++++++++++++--
 b/arch/x86/kernel/cpu/common.c     |   12 ++++++------
 b/arch/x86/kernel/setup.c          |    1 +
 3 files changed, 21 insertions(+), 8 deletions(-)

diff -puN arch/x86/include/asm/processor.h~no-cpu-data-phys_bits arch/x86/include/asm/processor.h
--- a/arch/x86/include/asm/processor.h~no-cpu-data-phys_bits	2024-02-22 10:08:56.220757996 -0800
+++ b/arch/x86/include/asm/processor.h	2024-02-22 10:08:56.228758310 -0800
@@ -118,7 +118,6 @@ struct cpuinfo_x86 {
 	__u32			vmx_capability[NVMXINTS];
 #endif
 	__u8			x86_virt_bits;
-	__u8			x86_phys_bits;
 	/* CPUID returned core id bits: */
 	__u8			x86_coreid_bits;
 	/* Max extended CPUID function supported: */
@@ -176,6 +175,19 @@ struct x86_addr_config {
 	u8 phys_addr_reduction_bits;
 };
 
+/*
+ * System-wide configuration that is shared by all processors.
+ *
+ * Built in early_cpu_init() on the boot CPU and and never
+ * modified after that.
+ */
+struct x86_sys_config {
+	/* Physical address bits supported by all processors */
+	u8	phys_bits;
+};
+
+extern struct x86_sys_config x86_config;
+
 #define X86_VENDOR_INTEL	0
 #define X86_VENDOR_CYRIX	1
 #define X86_VENDOR_AMD		2
@@ -783,7 +795,7 @@ static inline void weak_wrmsr_fence(void
 
 static inline u8 x86_phys_bits(void)
 {
-	return boot_cpu_data.x86_phys_bits;
+	return x86_config.phys_bits;
 }
 
 static inline u8 x86_virt_bits(void)
diff -puN arch/x86/kernel/cpu/common.c~no-cpu-data-phys_bits arch/x86/kernel/cpu/common.c
--- a/arch/x86/kernel/cpu/common.c~no-cpu-data-phys_bits	2024-02-22 10:08:56.224758153 -0800
+++ b/arch/x86/kernel/cpu/common.c	2024-02-22 10:08:56.228758310 -0800
@@ -1107,27 +1107,27 @@ void get_cpu_address_sizes(struct cpuinf
 		cpuid(0x80000008, &eax, &ebx, &ecx, &edx);
 
 		c->x86_virt_bits = (eax >> 8) & 0xff;
-		c->x86_phys_bits = eax & 0xff;
+		x86_config.phys_bits = eax & 0xff;
 	} else {
 		if (IS_ENABLED(CONFIG_X86_64)) {
+			x86_config.phys_bits = 36;
 			c->x86_clflush_size = 64;
-			c->x86_phys_bits = 36;
 			c->x86_virt_bits = 48;
 		} else {
+			x86_config.phys_bits = 32;
 			c->x86_clflush_size = 32;
 			c->x86_virt_bits = 32;
-			c->x86_phys_bits = 32;
 
 			if (cpu_has(c, X86_FEATURE_PAE) ||
 			    cpu_has(c, X86_FEATURE_PSE36))
-				c->x86_phys_bits = 36;
+				x86_config.phys_bits = 36;
 		}
 	}
-	c->x86_cache_bits = c->x86_phys_bits;
+	c->x86_cache_bits = x86_config.phys_bits;
 	c->x86_cache_alignment = x86_clflush_size();
 
 	/* Do this last to avoid affecting ->x86_cache_bits. */
-	c->x86_phys_bits -= bsp_addr_config.phys_addr_reduction_bits;
+	x86_config.phys_bits -= bsp_addr_config.phys_addr_reduction_bits;
 }
 
 static void identify_cpu_without_cpuid(struct cpuinfo_x86 *c)
diff -puN arch/x86/kernel/setup.c~no-cpu-data-phys_bits arch/x86/kernel/setup.c
--- a/arch/x86/kernel/setup.c~no-cpu-data-phys_bits	2024-02-22 10:08:56.224758153 -0800
+++ b/arch/x86/kernel/setup.c	2024-02-22 10:08:56.228758310 -0800
@@ -132,6 +132,7 @@ struct cpuinfo_x86 boot_cpu_data __read_
 EXPORT_SYMBOL(boot_cpu_data);
 
 struct x86_addr_config bsp_addr_config;
+struct x86_sys_config x86_config __read_mostly;
 
 #if !defined(CONFIG_X86_PAE) || defined(CONFIG_X86_64)
 __visible unsigned long mmu_cr4_features __ro_after_init;
_