KVM: x86: Fix BUILD_BUG() in __cpuid_entry_get_reg() w/ CONFIG_UBSAN=y
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Message ID 20200325191259.23559-1-sean.j.christopherson@intel.com
State New
Headers show
Series
  • KVM: x86: Fix BUILD_BUG() in __cpuid_entry_get_reg() w/ CONFIG_UBSAN=y
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Commit Message

Sean Christopherson March 25, 2020, 7:12 p.m. UTC
Take the target reg in __cpuid_entry_get_reg() instead of a pointer to a
struct cpuid_reg.  When building with -fsanitize=alignment (enabled by
CONFIG_UBSAN=y), some versions of gcc get tripped up on the pointer and
trigger the BUILD_BUG().

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Fixes: d8577a4c238f8 ("KVM: x86: Do host CPUID at load time to mask KVM cpu caps")
Fixes: 4c61534aaae2a ("KVM: x86: Introduce cpuid_entry_{get,has}() accessors")
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/x86/kvm/cpuid.c | 2 +-
 arch/x86/kvm/cpuid.h | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

Comments

Randy Dunlap March 25, 2020, 7:21 p.m. UTC | #1
On 3/25/20 12:12 PM, Sean Christopherson wrote:
> Take the target reg in __cpuid_entry_get_reg() instead of a pointer to a
> struct cpuid_reg.  When building with -fsanitize=alignment (enabled by
> CONFIG_UBSAN=y), some versions of gcc get tripped up on the pointer and
> trigger the BUILD_BUG().
> 
> Reported-by: Randy Dunlap <rdunlap@infradead.org>
> Fixes: d8577a4c238f8 ("KVM: x86: Do host CPUID at load time to mask KVM cpu caps")
> Fixes: 4c61534aaae2a ("KVM: x86: Introduce cpuid_entry_{get,has}() accessors")
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>

LGTM. Thanks.

Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested

> ---
>  arch/x86/kvm/cpuid.c | 2 +-
>  arch/x86/kvm/cpuid.h | 8 ++++----
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 08280d8a2ac9..16d3ae432420 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -269,7 +269,7 @@ static __always_inline void kvm_cpu_cap_mask(enum cpuid_leafs leaf, u32 mask)
>  	cpuid_count(cpuid.function, cpuid.index,
>  		    &entry.eax, &entry.ebx, &entry.ecx, &entry.edx);
>  
> -	kvm_cpu_caps[leaf] &= *__cpuid_entry_get_reg(&entry, &cpuid);
> +	kvm_cpu_caps[leaf] &= *__cpuid_entry_get_reg(&entry, cpuid.reg);
>  }
>  
>  void kvm_set_cpu_caps(void)
> diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
> index 23b4cd1ad986..63a70f6a3df3 100644
> --- a/arch/x86/kvm/cpuid.h
> +++ b/arch/x86/kvm/cpuid.h
> @@ -99,9 +99,9 @@ static __always_inline struct cpuid_reg x86_feature_cpuid(unsigned int x86_featu
>  }
>  
>  static __always_inline u32 *__cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
> -						  const struct cpuid_reg *cpuid)
> +						  u32 reg)
>  {
> -	switch (cpuid->reg) {
> +	switch (reg) {
>  	case CPUID_EAX:
>  		return &entry->eax;
>  	case CPUID_EBX:
> @@ -121,7 +121,7 @@ static __always_inline u32 *cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
>  {
>  	const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature);
>  
> -	return __cpuid_entry_get_reg(entry, &cpuid);
> +	return __cpuid_entry_get_reg(entry, cpuid.reg);
>  }
>  
>  static __always_inline u32 cpuid_entry_get(struct kvm_cpuid_entry2 *entry,
> @@ -189,7 +189,7 @@ static __always_inline u32 *guest_cpuid_get_register(struct kvm_vcpu *vcpu,
>  	if (!entry)
>  		return NULL;
>  
> -	return __cpuid_entry_get_reg(entry, &cpuid);
> +	return __cpuid_entry_get_reg(entry, cpuid.reg);
>  }
>  
>  static __always_inline bool guest_cpuid_has(struct kvm_vcpu *vcpu,
>
Paolo Bonzini March 31, 2020, 2:51 p.m. UTC | #2
On 25/03/20 20:12, Sean Christopherson wrote:
> Take the target reg in __cpuid_entry_get_reg() instead of a pointer to a
> struct cpuid_reg.  When building with -fsanitize=alignment (enabled by
> CONFIG_UBSAN=y), some versions of gcc get tripped up on the pointer and
> trigger the BUILD_BUG().
> 
> Reported-by: Randy Dunlap <rdunlap@infradead.org>
> Fixes: d8577a4c238f8 ("KVM: x86: Do host CPUID at load time to mask KVM cpu caps")
> Fixes: 4c61534aaae2a ("KVM: x86: Introduce cpuid_entry_{get,has}() accessors")
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
>  arch/x86/kvm/cpuid.c | 2 +-
>  arch/x86/kvm/cpuid.h | 8 ++++----
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 08280d8a2ac9..16d3ae432420 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -269,7 +269,7 @@ static __always_inline void kvm_cpu_cap_mask(enum cpuid_leafs leaf, u32 mask)
>  	cpuid_count(cpuid.function, cpuid.index,
>  		    &entry.eax, &entry.ebx, &entry.ecx, &entry.edx);
>  
> -	kvm_cpu_caps[leaf] &= *__cpuid_entry_get_reg(&entry, &cpuid);
> +	kvm_cpu_caps[leaf] &= *__cpuid_entry_get_reg(&entry, cpuid.reg);
>  }
>  
>  void kvm_set_cpu_caps(void)
> diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
> index 23b4cd1ad986..63a70f6a3df3 100644
> --- a/arch/x86/kvm/cpuid.h
> +++ b/arch/x86/kvm/cpuid.h
> @@ -99,9 +99,9 @@ static __always_inline struct cpuid_reg x86_feature_cpuid(unsigned int x86_featu
>  }
>  
>  static __always_inline u32 *__cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
> -						  const struct cpuid_reg *cpuid)
> +						  u32 reg)
>  {
> -	switch (cpuid->reg) {
> +	switch (reg) {
>  	case CPUID_EAX:
>  		return &entry->eax;
>  	case CPUID_EBX:
> @@ -121,7 +121,7 @@ static __always_inline u32 *cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
>  {
>  	const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature);
>  
> -	return __cpuid_entry_get_reg(entry, &cpuid);
> +	return __cpuid_entry_get_reg(entry, cpuid.reg);
>  }
>  
>  static __always_inline u32 cpuid_entry_get(struct kvm_cpuid_entry2 *entry,
> @@ -189,7 +189,7 @@ static __always_inline u32 *guest_cpuid_get_register(struct kvm_vcpu *vcpu,
>  	if (!entry)
>  		return NULL;
>  
> -	return __cpuid_entry_get_reg(entry, &cpuid);
> +	return __cpuid_entry_get_reg(entry, cpuid.reg);
>  }
>  
>  static __always_inline bool guest_cpuid_has(struct kvm_vcpu *vcpu,
> 

Queued, thanks.

Paolo

Patch
diff mbox series

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 08280d8a2ac9..16d3ae432420 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -269,7 +269,7 @@  static __always_inline void kvm_cpu_cap_mask(enum cpuid_leafs leaf, u32 mask)
 	cpuid_count(cpuid.function, cpuid.index,
 		    &entry.eax, &entry.ebx, &entry.ecx, &entry.edx);
 
-	kvm_cpu_caps[leaf] &= *__cpuid_entry_get_reg(&entry, &cpuid);
+	kvm_cpu_caps[leaf] &= *__cpuid_entry_get_reg(&entry, cpuid.reg);
 }
 
 void kvm_set_cpu_caps(void)
diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index 23b4cd1ad986..63a70f6a3df3 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -99,9 +99,9 @@  static __always_inline struct cpuid_reg x86_feature_cpuid(unsigned int x86_featu
 }
 
 static __always_inline u32 *__cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
-						  const struct cpuid_reg *cpuid)
+						  u32 reg)
 {
-	switch (cpuid->reg) {
+	switch (reg) {
 	case CPUID_EAX:
 		return &entry->eax;
 	case CPUID_EBX:
@@ -121,7 +121,7 @@  static __always_inline u32 *cpuid_entry_get_reg(struct kvm_cpuid_entry2 *entry,
 {
 	const struct cpuid_reg cpuid = x86_feature_cpuid(x86_feature);
 
-	return __cpuid_entry_get_reg(entry, &cpuid);
+	return __cpuid_entry_get_reg(entry, cpuid.reg);
 }
 
 static __always_inline u32 cpuid_entry_get(struct kvm_cpuid_entry2 *entry,
@@ -189,7 +189,7 @@  static __always_inline u32 *guest_cpuid_get_register(struct kvm_vcpu *vcpu,
 	if (!entry)
 		return NULL;
 
-	return __cpuid_entry_get_reg(entry, &cpuid);
+	return __cpuid_entry_get_reg(entry, cpuid.reg);
 }
 
 static __always_inline bool guest_cpuid_has(struct kvm_vcpu *vcpu,