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[1/2] kvm-unit-test: x86: Add a wrapper to check if the CPU supports NX bit in MSR_EFER

Message ID 20190522234545.5930-2-krish.sadhukhan@oracle.com (mailing list archive)
State New, archived
Headers show
Series kvm-unit-test: nVMX: Test "Load IA32_EFER" VM-exit control on vmentry of nested guests | expand

Commit Message

Krish Sadhukhan May 22, 2019, 11:45 p.m. UTC 
Signed-off-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
Reviewed-by: Karl Heubaum <karl.heubaum@oracle.com>
---
 lib/x86/processor.h | 8 ++++++++
 x86/vmexit.c        | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

Comments

Jim Mattson May 23, 2019, 4:58 p.m. UTC | #1 
On Wed, May 22, 2019 at 5:12 PM Krish Sadhukhan
<krish.sadhukhan@oracle.com> wrote:
>
> Signed-off-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
> Reviewed-by: Karl Heubaum <karl.heubaum@oracle.com>
There will likely be a lot of these over time. Why not implement
something more generic, like static_cpu_has() in the kernel?
Sean Christopherson June 4, 2019, 1:59 p.m. UTC | #2 
On Wed, May 22, 2019 at 07:45:44PM -0400, Krish Sadhukhan wrote:
> Signed-off-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
> Reviewed-by: Karl Heubaum <karl.heubaum@oracle.com>
> ---
>  lib/x86/processor.h | 8 ++++++++
>  x86/vmexit.c        | 2 +-
>  2 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/x86/processor.h b/lib/x86/processor.h
> index 15237a5..2ca988e 100644
> --- a/lib/x86/processor.h
> +++ b/lib/x86/processor.h
> @@ -476,4 +476,12 @@ static inline void set_bit(int bit, u8 *addr)
>  			     : "+m" (*addr) : "Ir" (bit) : "cc", "memory");
>  }
>  
> +static inline int efer_nx_enabled(void)

cpu_has_efer_nx() would be more appropriate.  Most readers would expect
"enabled" to mean we're checking MSR_EFER.NX==1.

This can have a boolean return value.

> +{
> +	if (cpuid(0x80000001).d & (1 << 20))
> +		return 1;
> +	else
> +		return 0;
> +}

This can simply be:

    return cpuid(0x80000001).d & (1 << 20);

or if gcc complains about boolean stuff:

    return !!(cpuid(0x80000001).d & (1 << 20));
> +
>  #endif
> diff --git a/x86/vmexit.c b/x86/vmexit.c
> index c12dd24..7053a46 100644
> --- a/x86/vmexit.c
> +++ b/x86/vmexit.c
> @@ -526,7 +526,7 @@ static bool do_test(struct test *test)
>  
>  static void enable_nx(void *junk)
>  {
> -	if (cpuid(0x80000001).d & (1 << 20))
> +	if (efer_nx_enabled())
>  		wrmsr(MSR_EFER, rdmsr(MSR_EFER) | EFER_NX_MASK);
>  }
>  
> -- 
> 2.20.1
>
diff mbox series

Patch

diff --git a/lib/x86/processor.h b/lib/x86/processor.h
index 15237a5..2ca988e 100644
--- a/lib/x86/processor.h
+++ b/lib/x86/processor.h
@@ -476,4 +476,12 @@  static inline void set_bit(int bit, u8 *addr)
 			     : "+m" (*addr) : "Ir" (bit) : "cc", "memory");
 }
 
+static inline int efer_nx_enabled(void)
+{
+	if (cpuid(0x80000001).d & (1 << 20))
+		return 1;
+	else
+		return 0;
+}
+
 #endif
diff --git a/x86/vmexit.c b/x86/vmexit.c
index c12dd24..7053a46 100644
--- a/x86/vmexit.c
+++ b/x86/vmexit.c
@@ -526,7 +526,7 @@  static bool do_test(struct test *test)
 
 static void enable_nx(void *junk)
 {
-	if (cpuid(0x80000001).d & (1 << 20))
+	if (efer_nx_enabled())
 		wrmsr(MSR_EFER, rdmsr(MSR_EFER) | EFER_NX_MASK);
 }