[tip:x86/cpu] x86/CPU: Change query logic so CPUID is enabled before testing
Commit-ID: 2893cc8ff892fa74972d8dc0e1d0dc65116daaa3
Gitweb: https://git.kernel.org/tip/2893cc8ff892fa74972d8dc0e1d0dc65116daaa3
Author: Matthew Whitehead
AuthorDate: Fri, 21 Sep 2018 17:20:41 -0400
Committer: Borislav Petkov
CommitDate: Sat, 22 Sep 2018 11:47:39 +0200
x86/CPU: Change query logic so CPUID is enabled before testing
Presently we check first if CPUID is enabled. If it is not already
enabled, then we next call identify_cpu_without_cpuid() and clear
X86_FEATURE_CPUID.
Unfortunately, identify_cpu_without_cpuid() is the function where CPUID
becomes _enabled_ on Cyrix 6x86/6x86L CPUs.
Reverse the calling sequence so that CPUID is first enabled, and then
check a second time to see if the feature has now been activated.
[ bp: Massage commit message and remove trailing whitespace. ]
Suggested-by: Andy Lutomirski
Signed-off-by: Matthew Whitehead
Signed-off-by: Borislav Petkov
Reviewed-by: Andy Lutomirski
Cc: David Woodhouse
Cc: H. Peter Anvin
Cc: Ingo Molnar
Cc: Konrad Rzeszutek Wilk
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/20180921212041.13096-3-tedheads...@gmail.com
---
arch/x86/kernel/cpu/common.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 44c4ef3d989b..658c85d16a9b 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1076,6 +1076,9 @@ static void __init early_identify_cpu(struct cpuinfo_x86
*c)
memset(>x86_capability, 0, sizeof c->x86_capability);
c->extended_cpuid_level = 0;
+ if (!have_cpuid_p())
+ identify_cpu_without_cpuid(c);
+
/* cyrix could have cpuid enabled via c_identify()*/
if (have_cpuid_p()) {
cpu_detect(c);
@@ -1093,7 +1096,6 @@ static void __init early_identify_cpu(struct cpuinfo_x86
*c)
if (this_cpu->c_bsp_init)
this_cpu->c_bsp_init(c);
} else {
- identify_cpu_without_cpuid(c);
setup_clear_cpu_cap(X86_FEATURE_CPUID);
}
[tip:x86/cpu] x86/CPU: Change query logic so CPUID is enabled before testing
Commit-ID: 2893cc8ff892fa74972d8dc0e1d0dc65116daaa3
Gitweb: https://git.kernel.org/tip/2893cc8ff892fa74972d8dc0e1d0dc65116daaa3
Author: Matthew Whitehead
AuthorDate: Fri, 21 Sep 2018 17:20:41 -0400
Committer: Borislav Petkov
CommitDate: Sat, 22 Sep 2018 11:47:39 +0200
x86/CPU: Change query logic so CPUID is enabled before testing
Presently we check first if CPUID is enabled. If it is not already
enabled, then we next call identify_cpu_without_cpuid() and clear
X86_FEATURE_CPUID.
Unfortunately, identify_cpu_without_cpuid() is the function where CPUID
becomes _enabled_ on Cyrix 6x86/6x86L CPUs.
Reverse the calling sequence so that CPUID is first enabled, and then
check a second time to see if the feature has now been activated.
[ bp: Massage commit message and remove trailing whitespace. ]
Suggested-by: Andy Lutomirski
Signed-off-by: Matthew Whitehead
Signed-off-by: Borislav Petkov
Reviewed-by: Andy Lutomirski
Cc: David Woodhouse
Cc: H. Peter Anvin
Cc: Ingo Molnar
Cc: Konrad Rzeszutek Wilk
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/20180921212041.13096-3-tedheads...@gmail.com
---
arch/x86/kernel/cpu/common.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 44c4ef3d989b..658c85d16a9b 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1076,6 +1076,9 @@ static void __init early_identify_cpu(struct cpuinfo_x86
*c)
memset(>x86_capability, 0, sizeof c->x86_capability);
c->extended_cpuid_level = 0;
+ if (!have_cpuid_p())
+ identify_cpu_without_cpuid(c);
+
/* cyrix could have cpuid enabled via c_identify()*/
if (have_cpuid_p()) {
cpu_detect(c);
@@ -1093,7 +1096,6 @@ static void __init early_identify_cpu(struct cpuinfo_x86
*c)
if (this_cpu->c_bsp_init)
this_cpu->c_bsp_init(c);
} else {
- identify_cpu_without_cpuid(c);
setup_clear_cpu_cap(X86_FEATURE_CPUID);
}
