linux-kernel - [RFC][PATCH 17/34] x86/cpu: Move virtual address limit out of cpuinfo

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Date: Thu, 22 Feb 2024 10:39:49 -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 17/34] x86/cpu: Move virtual 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_virt_bits.  The only remaining references are to
'boot_cpu_data' via the x86_virt_bits() helper.

This means the farce that x86_virt_bits is per-cpu data can end.
Remove it from cpuinfo_x86 and add it to 'x86_config'.

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

 b/arch/x86/include/asm/processor.h |    6 +++---
 b/arch/x86/kernel/cpu/common.c     |    8 +++-----
 b/arch/x86/mm/maccess.c            |    9 +++++----
 3 files changed, 11 insertions(+), 12 deletions(-)

diff -puN arch/x86/include/asm/processor.h~no-cpu-data-virt_bits arch/x86/include/asm/processor.h
--- a/arch/x86/include/asm/processor.h~no-cpu-data-virt_bits	2024-02-22 10:08:56.748778725 -0800
+++ b/arch/x86/include/asm/processor.h	2024-02-22 10:08:56.752778882 -0800
@@ -117,7 +117,6 @@ struct cpuinfo_x86 {
 #ifdef CONFIG_X86_VMX_FEATURE_NAMES
 	__u32			vmx_capability[NVMXINTS];
 #endif
-	__u8			x86_virt_bits;
 	/* CPUID returned core id bits: */
 	__u8			x86_coreid_bits;
 	/* Max extended CPUID function supported: */
@@ -182,8 +181,9 @@ struct x86_addr_config {
  * modified after that.
  */
 struct x86_sys_config {
-	/* Physical address bits supported by all processors */
+	/* Address bits supported by all processors */
 	u8	phys_bits;
+	u8	virt_bits;
 };
 
 extern struct x86_sys_config x86_config;
@@ -800,7 +800,7 @@ static inline u8 x86_phys_bits(void)
 
 static inline u8 x86_virt_bits(void)
 {
-	return boot_cpu_data.x86_virt_bits;
+	return x86_config.virt_bits;
 }
 
 static inline u8 x86_clflush_size(void)
diff -puN arch/x86/kernel/cpu/common.c~no-cpu-data-virt_bits arch/x86/kernel/cpu/common.c
--- a/arch/x86/kernel/cpu/common.c~no-cpu-data-virt_bits	2024-02-22 10:08:56.748778725 -0800
+++ b/arch/x86/kernel/cpu/common.c	2024-02-22 10:08:56.752778882 -0800
@@ -1106,17 +1106,17 @@ void get_cpu_address_sizes(struct cpuinf
 	if (vp_bits_from_cpuid) {
 		cpuid(0x80000008, &eax, &ebx, &ecx, &edx);
 
-		c->x86_virt_bits = (eax >> 8) & 0xff;
+		x86_config.virt_bits = (eax >> 8) & 0xff;
 		x86_config.phys_bits = eax & 0xff;
 	} else {
 		if (IS_ENABLED(CONFIG_X86_64)) {
 			x86_config.phys_bits = 36;
+			x86_config.virt_bits = 48;
 			c->x86_clflush_size = 64;
-			c->x86_virt_bits = 48;
 		} else {
 			x86_config.phys_bits = 32;
+			x86_config.virt_bits = 32;
 			c->x86_clflush_size = 32;
-			c->x86_virt_bits = 32;
 
 			if (cpu_has(c, X86_FEATURE_PAE) ||
 			    cpu_has(c, X86_FEATURE_PSE36))
@@ -1827,11 +1827,9 @@ static void identify_cpu(struct cpuinfo_
 	c->topo.l2c_id = BAD_APICID;
 #ifdef CONFIG_X86_64
 	c->x86_clflush_size = 64;
-	c->x86_virt_bits = 48;
 #else
 	c->cpuid_level = -1;	/* CPUID not detected */
 	c->x86_clflush_size = 32;
-	c->x86_virt_bits = 32;
 #endif
 	c->x86_cache_alignment = x86_clflush_size();
 	memset(&c->x86_capability, 0, sizeof(c->x86_capability));
diff -puN arch/x86/mm/maccess.c~no-cpu-data-virt_bits arch/x86/mm/maccess.c
--- a/arch/x86/mm/maccess.c~no-cpu-data-virt_bits	2024-02-22 10:08:56.752778882 -0800
+++ b/arch/x86/mm/maccess.c	2024-02-22 10:08:56.752778882 -0800
@@ -16,11 +16,12 @@ bool copy_from_kernel_nofault_allowed(co
 		return false;
 
 	/*
-	 * Allow everything during early boot before 'x86_virt_bits'
-	 * is initialized.  Needed for instruction decoding in early
-	 * exception handlers.
+	 * Allow everything during early boot before 'virt_bits' is
+	 * initialized.  Needed for instruction decoding in early
+	 * exception handlers.  Avoid the helper because it may do
+	 * error checking for being uninitiazed.
 	 */
-	if (!x86_virt_bits())
+	if (!x86_config.virt_bits)
 		return true;
 
 	return __is_canonical_address(vaddr, x86_virt_bits());
_