[PATCH v2 07/10] x86/mm: Disable PCID on 32-bit kernels

[Andy Lutomirski]

32-bit kernels on new hardware will see PCID in CPUID, but PCID can
only be used in 64-bit mode.  Rather than making all PCID code
conditional, just disable the feature on 32-bit builds.

Signed-off-by: Andy Lutomirski 
---
 arch/x86/include/asm/disabled-features.h | 4 +++-
 arch/x86/kernel/cpu/bugs.c   | 8 
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/disabled-features.h 
b/arch/x86/include/asm/disabled-features.h
index 5dff775af7cd..c10c9128f54e 100644
--- a/arch/x86/include/asm/disabled-features.h
+++ b/arch/x86/include/asm/disabled-features.h
@@ -21,11 +21,13 @@
 # define DISABLE_K6_MTRR   (1<<(X86_FEATURE_K6_MTRR & 31))
 # define DISABLE_CYRIX_ARR (1<<(X86_FEATURE_CYRIX_ARR & 31))
 # define DISABLE_CENTAUR_MCR   (1<<(X86_FEATURE_CENTAUR_MCR & 31))
+# define DISABLE_PCID  0
 #else
 # define DISABLE_VME   0
 # define DISABLE_K6_MTRR   0
 # define DISABLE_CYRIX_ARR 0
 # define DISABLE_CENTAUR_MCR   0
+# define DISABLE_PCID  (1<<(X86_FEATURE_PCID & 31))
 #endif /* CONFIG_X86_64 */
 
 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
@@ -49,7 +51,7 @@
 #define DISABLED_MASK1 0
 #define DISABLED_MASK2 0
 #define DISABLED_MASK3 (DISABLE_CYRIX_ARR|DISABLE_CENTAUR_MCR|DISABLE_K6_MTRR)
-#define DISABLED_MASK4 0
+#define DISABLED_MASK4 (DISABLE_PCID)
 #define DISABLED_MASK5 0
 #define DISABLED_MASK6 0
 #define DISABLED_MASK7 0
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 0af86d9242da..db684880d74a 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -21,6 +21,14 @@
 
 void __init check_bugs(void)
 {
+#ifdef CONFIG_X86_32
+   /*
+* Regardless of whether PCID is enumerated, the SDM says
+* that it can't be enabled in 32-bit mode.
+*/
+   setup_clear_cpu_cap(X86_FEATURE_PCID);
+#endif
+
identify_boot_cpu();
 
if (!IS_ENABLED(CONFIG_SMP)) {
-- 
2.9.4

[PATCH v2 07/10] x86/mm: Disable PCID on 32-bit kernels

[Andy Lutomirski]

32-bit kernels on new hardware will see PCID in CPUID, but PCID can
only be used in 64-bit mode.  Rather than making all PCID code
conditional, just disable the feature on 32-bit builds.

Signed-off-by: Andy Lutomirski 
---
 arch/x86/include/asm/disabled-features.h | 4 +++-
 arch/x86/kernel/cpu/bugs.c   | 8 
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/disabled-features.h 
b/arch/x86/include/asm/disabled-features.h
index 5dff775af7cd..c10c9128f54e 100644
--- a/arch/x86/include/asm/disabled-features.h
+++ b/arch/x86/include/asm/disabled-features.h
@@ -21,11 +21,13 @@
 # define DISABLE_K6_MTRR   (1<<(X86_FEATURE_K6_MTRR & 31))
 # define DISABLE_CYRIX_ARR (1<<(X86_FEATURE_CYRIX_ARR & 31))
 # define DISABLE_CENTAUR_MCR   (1<<(X86_FEATURE_CENTAUR_MCR & 31))
+# define DISABLE_PCID  0
 #else
 # define DISABLE_VME   0
 # define DISABLE_K6_MTRR   0
 # define DISABLE_CYRIX_ARR 0
 # define DISABLE_CENTAUR_MCR   0
+# define DISABLE_PCID  (1<<(X86_FEATURE_PCID & 31))
 #endif /* CONFIG_X86_64 */
 
 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
@@ -49,7 +51,7 @@
 #define DISABLED_MASK1 0
 #define DISABLED_MASK2 0
 #define DISABLED_MASK3 (DISABLE_CYRIX_ARR|DISABLE_CENTAUR_MCR|DISABLE_K6_MTRR)
-#define DISABLED_MASK4 0
+#define DISABLED_MASK4 (DISABLE_PCID)
 #define DISABLED_MASK5 0
 #define DISABLED_MASK6 0
 #define DISABLED_MASK7 0
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 0af86d9242da..db684880d74a 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -21,6 +21,14 @@
 
 void __init check_bugs(void)
 {
+#ifdef CONFIG_X86_32
+   /*
+* Regardless of whether PCID is enumerated, the SDM says
+* that it can't be enabled in 32-bit mode.
+*/
+   setup_clear_cpu_cap(X86_FEATURE_PCID);
+#endif
+
identify_boot_cpu();
 
if (!IS_ENABLED(CONFIG_SMP)) {
-- 
2.9.4