[1/2] KVM: CPUID: Check limit first when emulating CPUID instruction
diff mbox series

Message ID 20190910082442.142702-2-xiaoyao.li@intel.com
State New
Headers show
Series
  • KVM: CPUID: CPUID emulation flow adjustment and one minor refinement when updating maxphyaddr
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Commit Message

Xiaoyao Li Sept. 10, 2019, 8:24 a.m. UTC
When limit checking is required, it should be executed first, which is
consistent with the CPUID specification.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
---
 arch/x86/kvm/cpuid.c | 50 +++++++++++++++++++++++++-------------------
 1 file changed, 28 insertions(+), 22 deletions(-)

Comments

Xiaoyao Li Sept. 10, 2019, 9:52 a.m. UTC | #1
On Tue, 2019-09-10 at 16:24 +0800, Xiaoyao Li wrote:
> When limit checking is required, it should be executed first, which is
> consistent with the CPUID specification.
> 
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---
>  arch/x86/kvm/cpuid.c | 50 +++++++++++++++++++++++++-------------------
>  1 file changed, 28 insertions(+), 22 deletions(-)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 22c2720cd948..866546b4d834 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -952,23 +952,33 @@ struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct
> kvm_vcpu *vcpu,
>  EXPORT_SYMBOL_GPL(kvm_find_cpuid_entry);
>  
>  /*
> - * If no match is found, check whether we exceed the vCPU's limit
> - * and return the content of the highest valid _standard_ leaf instead.
> - * This is to satisfy the CPUID specification.
> + * Based on CPUID specification, if leaf number exceeds the vCPU's limit,
> + * it should return the content of the highest valid _standard_ leaf instead.
> + * Note: *found is set true only means the queried leaf number doesn't exceed
> + * the maximum leaf number of basic or extented leaf.
>   */
> -static struct kvm_cpuid_entry2* check_cpuid_limit(struct kvm_vcpu *vcpu,
> -                                                  u32 function, u32 index)
> +static struct kvm_cpuid_entry2* cpuid_check_limit(struct kvm_vcpu *vcpu,
> +                                                  u32 function, u32 index,
> +						  bool *found)
>  {
>  	struct kvm_cpuid_entry2 *maxlevel;
>  
>  	maxlevel = kvm_find_cpuid_entry(vcpu, function & 0x80000000, 0);
> -	if (!maxlevel || maxlevel->eax >= function)
> +	if (!maxlevel)
>  		return NULL;
> -	if (function & 0x80000000) {
> -		maxlevel = kvm_find_cpuid_entry(vcpu, 0, 0);
> -		if (!maxlevel)
> -			return NULL;
> +
> +	if (maxlevel->eax >= function) {
> +		if (found)
> +			*found = true;
> +		return kvm_find_cpuid_entry(vcpu, function, index);
>  	}
> +
> +	if (function & 0x80000000)
> +		maxlevel = kvm_find_cpuid_entry(vcpu, 0, 0);
> +
> +	if (!maxlevel)
> +		return NULL;
> +
>  	return kvm_find_cpuid_entry(vcpu, maxlevel->eax, index);
>  }
>  
> @@ -977,26 +987,22 @@ bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32
> *ebx,
>  {
>  	u32 function = *eax, index = *ecx;
>  	struct kvm_cpuid_entry2 *best;
> -	bool entry_found = true;
> +	bool entry_found = false;
>  
> -	best = kvm_find_cpuid_entry(vcpu, function, index);
> +	if (check_limit)
> +		best = cpuid_check_limit(vcpu, function, index, &entry_found);
> +	else
> +		best = kvm_find_cpuid_entry(vcpu, function, index);
>  
> -	if (!best) {
> -		entry_found = false;
> -		if (!check_limit)
> -			goto out;
> -
> -		best = check_cpuid_limit(vcpu, function, index);
> -	}
> -
> -out:
>  	if (best) {
>  		*eax = best->eax;
>  		*ebx = best->ebx;
>  		*ecx = best->ecx;
>  		*edx = best->edx;
> -	} else
> +	} else {
> +		entry_found = false;
>  		*eax = *ebx = *ecx = *edx = 0;
> +	}
>  	trace_kvm_cpuid(function, *eax, *ebx, *ecx, *edx, entry_found);
>  	return entry_found;
>  }

Just realise the entry_found is not set true if found in no limit checking case.
Will send v2.

Patch
diff mbox series

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 22c2720cd948..866546b4d834 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -952,23 +952,33 @@  struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
 EXPORT_SYMBOL_GPL(kvm_find_cpuid_entry);
 
 /*
- * If no match is found, check whether we exceed the vCPU's limit
- * and return the content of the highest valid _standard_ leaf instead.
- * This is to satisfy the CPUID specification.
+ * Based on CPUID specification, if leaf number exceeds the vCPU's limit,
+ * it should return the content of the highest valid _standard_ leaf instead.
+ * Note: *found is set true only means the queried leaf number doesn't exceed
+ * the maximum leaf number of basic or extented leaf.
  */
-static struct kvm_cpuid_entry2* check_cpuid_limit(struct kvm_vcpu *vcpu,
-                                                  u32 function, u32 index)
+static struct kvm_cpuid_entry2* cpuid_check_limit(struct kvm_vcpu *vcpu,
+                                                  u32 function, u32 index,
+						  bool *found)
 {
 	struct kvm_cpuid_entry2 *maxlevel;
 
 	maxlevel = kvm_find_cpuid_entry(vcpu, function & 0x80000000, 0);
-	if (!maxlevel || maxlevel->eax >= function)
+	if (!maxlevel)
 		return NULL;
-	if (function & 0x80000000) {
-		maxlevel = kvm_find_cpuid_entry(vcpu, 0, 0);
-		if (!maxlevel)
-			return NULL;
+
+	if (maxlevel->eax >= function) {
+		if (found)
+			*found = true;
+		return kvm_find_cpuid_entry(vcpu, function, index);
 	}
+
+	if (function & 0x80000000)
+		maxlevel = kvm_find_cpuid_entry(vcpu, 0, 0);
+
+	if (!maxlevel)
+		return NULL;
+
 	return kvm_find_cpuid_entry(vcpu, maxlevel->eax, index);
 }
 
@@ -977,26 +987,22 @@  bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
 {
 	u32 function = *eax, index = *ecx;
 	struct kvm_cpuid_entry2 *best;
-	bool entry_found = true;
+	bool entry_found = false;
 
-	best = kvm_find_cpuid_entry(vcpu, function, index);
+	if (check_limit)
+		best = cpuid_check_limit(vcpu, function, index, &entry_found);
+	else
+		best = kvm_find_cpuid_entry(vcpu, function, index);
 
-	if (!best) {
-		entry_found = false;
-		if (!check_limit)
-			goto out;
-
-		best = check_cpuid_limit(vcpu, function, index);
-	}
-
-out:
 	if (best) {
 		*eax = best->eax;
 		*ebx = best->ebx;
 		*ecx = best->ecx;
 		*edx = best->edx;
-	} else
+	} else {
+		entry_found = false;
 		*eax = *ebx = *ecx = *edx = 0;
+	}
 	trace_kvm_cpuid(function, *eax, *ebx, *ecx, *edx, entry_found);
 	return entry_found;
 }