Re: [PATCH v2 2/2] x86/cpu: Change query logic so cpuid is enabled before testing
On Fri, Sep 21, 2018 at 2:21 PM Matthew Whitehead wrote:
>
> Presently we check for cpuid to be enabled first. 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. So we must 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.
>
> Reviewed-by: Andy Lutomirski
How about Suggested-and-reviewed-by: Andy Lutomirski instead?
(No need to resubmit for just that. Ingo or Thomas, if you like
these, can you just make that substitution?)
> Signed-off-by: Matthew Whitehead
> ---
> 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 eb4cb3efd20e..60c7c5ce7e55 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -1040,6 +1040,9 @@ 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);
> @@ -1057,7 +1060,6 @@ 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);
> }
>
> --
> 2.16.4
>
--
Andy Lutomirski
AMA Capital Management, LLC
Re: [PATCH v2 2/2] x86/cpu: Change query logic so cpuid is enabled before testing
On Fri, Sep 21, 2018 at 2:21 PM Matthew Whitehead wrote:
>
> Presently we check for cpuid to be enabled first. 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. So we must 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.
>
> Reviewed-by: Andy Lutomirski
How about Suggested-and-reviewed-by: Andy Lutomirski instead?
(No need to resubmit for just that. Ingo or Thomas, if you like
these, can you just make that substitution?)
> Signed-off-by: Matthew Whitehead
> ---
> 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 eb4cb3efd20e..60c7c5ce7e55 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -1040,6 +1040,9 @@ 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);
> @@ -1057,7 +1060,6 @@ 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);
> }
>
> --
> 2.16.4
>
--
Andy Lutomirski
AMA Capital Management, LLC
[PATCH v2 2/2] x86/cpu: Change query logic so cpuid is enabled before testing
Presently we check for cpuid to be enabled first. 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. So we must 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.
Reviewed-by: Andy Lutomirski
Signed-off-by: Matthew Whitehead
---
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 eb4cb3efd20e..60c7c5ce7e55 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1040,6 +1040,9 @@ 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);
@@ -1057,7 +1060,6 @@ 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);
}
--
2.16.4
[PATCH v2 2/2] x86/cpu: Change query logic so cpuid is enabled before testing
Presently we check for cpuid to be enabled first. 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. So we must 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.
Reviewed-by: Andy Lutomirski
Signed-off-by: Matthew Whitehead
---
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 eb4cb3efd20e..60c7c5ce7e55 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1040,6 +1040,9 @@ 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);
@@ -1057,7 +1060,6 @@ 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);
}
--
2.16.4
