[v3] x86: kvm: avoid -Wsometimes-uninitized warning
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Message ID 20190712141322.1073650-1-arnd@arndb.de
State New
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  • [v3] x86: kvm: avoid -Wsometimes-uninitized warning
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Commit Message

Arnd Bergmann July 12, 2019, 2:13 p.m. UTC
Clang notices a code path in which some variables are never
initialized, but fails to figure out that this can never happen
on i386 because is_64_bit_mode() always returns false.

arch/x86/kvm/hyperv.c:1610:6: error: variable 'ingpa' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
        if (!longmode) {
            ^~~~~~~~~
arch/x86/kvm/hyperv.c:1632:55: note: uninitialized use occurs here
        trace_kvm_hv_hypercall(code, fast, rep_cnt, rep_idx, ingpa, outgpa);
                                                             ^~~~~
arch/x86/kvm/hyperv.c:1610:2: note: remove the 'if' if its condition is always true
        if (!longmode) {
        ^~~~~~~~~~~~~~~
arch/x86/kvm/hyperv.c:1595:18: note: initialize the variable 'ingpa' to silence this warning
        u64 param, ingpa, outgpa, ret = HV_STATUS_SUCCESS;
                        ^
                         = 0
arch/x86/kvm/hyperv.c:1610:6: error: variable 'outgpa' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
arch/x86/kvm/hyperv.c:1610:6: error: variable 'param' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]

Flip the condition around to avoid the conditional execution on i386.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
v3: reword commit log, simplify patch again
v2: make the change inside of is_64_bit_mode().
---
 arch/x86/kvm/hyperv.c | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

Comments

Roman Kagan July 12, 2019, 4:33 p.m. UTC | #1
On Fri, Jul 12, 2019 at 04:13:09PM +0200, Arnd Bergmann wrote:
> Clang notices a code path in which some variables are never
> initialized, but fails to figure out that this can never happen
> on i386 because is_64_bit_mode() always returns false.
> 
> arch/x86/kvm/hyperv.c:1610:6: error: variable 'ingpa' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
>         if (!longmode) {
>             ^~~~~~~~~
> arch/x86/kvm/hyperv.c:1632:55: note: uninitialized use occurs here
>         trace_kvm_hv_hypercall(code, fast, rep_cnt, rep_idx, ingpa, outgpa);
>                                                              ^~~~~
> arch/x86/kvm/hyperv.c:1610:2: note: remove the 'if' if its condition is always true
>         if (!longmode) {
>         ^~~~~~~~~~~~~~~
> arch/x86/kvm/hyperv.c:1595:18: note: initialize the variable 'ingpa' to silence this warning
>         u64 param, ingpa, outgpa, ret = HV_STATUS_SUCCESS;
>                         ^
>                          = 0
> arch/x86/kvm/hyperv.c:1610:6: error: variable 'outgpa' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
> arch/x86/kvm/hyperv.c:1610:6: error: variable 'param' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
> 
> Flip the condition around to avoid the conditional execution on i386.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> v3: reword commit log, simplify patch again
> v2: make the change inside of is_64_bit_mode().
> ---
>  arch/x86/kvm/hyperv.c | 20 +++++++++-----------
>  1 file changed, 9 insertions(+), 11 deletions(-)

Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
Nathan Chancellor July 12, 2019, 5:44 p.m. UTC | #2
On Fri, Jul 12, 2019 at 04:13:09PM +0200, Arnd Bergmann wrote:
> Clang notices a code path in which some variables are never
> initialized, but fails to figure out that this can never happen
> on i386 because is_64_bit_mode() always returns false.
> 
> arch/x86/kvm/hyperv.c:1610:6: error: variable 'ingpa' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
>         if (!longmode) {
>             ^~~~~~~~~
> arch/x86/kvm/hyperv.c:1632:55: note: uninitialized use occurs here
>         trace_kvm_hv_hypercall(code, fast, rep_cnt, rep_idx, ingpa, outgpa);
>                                                              ^~~~~
> arch/x86/kvm/hyperv.c:1610:2: note: remove the 'if' if its condition is always true
>         if (!longmode) {
>         ^~~~~~~~~~~~~~~
> arch/x86/kvm/hyperv.c:1595:18: note: initialize the variable 'ingpa' to silence this warning
>         u64 param, ingpa, outgpa, ret = HV_STATUS_SUCCESS;
>                         ^
>                          = 0
> arch/x86/kvm/hyperv.c:1610:6: error: variable 'outgpa' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
> arch/x86/kvm/hyperv.c:1610:6: error: variable 'param' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
> 
> Flip the condition around to avoid the conditional execution on i386.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Paolo Bonzini July 12, 2019, 5:45 p.m. UTC | #3
On 12/07/19 16:13, Arnd Bergmann wrote:
> Clang notices a code path in which some variables are never
> initialized, but fails to figure out that this can never happen
> on i386 because is_64_bit_mode() always returns false.
> 
> arch/x86/kvm/hyperv.c:1610:6: error: variable 'ingpa' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
>         if (!longmode) {
>             ^~~~~~~~~
> arch/x86/kvm/hyperv.c:1632:55: note: uninitialized use occurs here
>         trace_kvm_hv_hypercall(code, fast, rep_cnt, rep_idx, ingpa, outgpa);
>                                                              ^~~~~
> arch/x86/kvm/hyperv.c:1610:2: note: remove the 'if' if its condition is always true
>         if (!longmode) {
>         ^~~~~~~~~~~~~~~
> arch/x86/kvm/hyperv.c:1595:18: note: initialize the variable 'ingpa' to silence this warning
>         u64 param, ingpa, outgpa, ret = HV_STATUS_SUCCESS;
>                         ^
>                          = 0
> arch/x86/kvm/hyperv.c:1610:6: error: variable 'outgpa' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
> arch/x86/kvm/hyperv.c:1610:6: error: variable 'param' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
> 
> Flip the condition around to avoid the conditional execution on i386.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> v3: reword commit log, simplify patch again
> v2: make the change inside of is_64_bit_mode().
> ---
>  arch/x86/kvm/hyperv.c | 20 +++++++++-----------
>  1 file changed, 9 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index a39e38f13029..c10a8b10b203 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -1594,7 +1594,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
>  {
>  	u64 param, ingpa, outgpa, ret = HV_STATUS_SUCCESS;
>  	uint16_t code, rep_idx, rep_cnt;
> -	bool fast, longmode, rep;
> +	bool fast, rep;
>  
>  	/*
>  	 * hypercall generates UD from non zero cpl and real mode
> @@ -1605,9 +1605,14 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
>  		return 1;
>  	}
>  
> -	longmode = is_64_bit_mode(vcpu);
> -
> -	if (!longmode) {
> +#ifdef CONFIG_X86_64
> +	if (is_64_bit_mode(vcpu)) {
> +		param = kvm_rcx_read(vcpu);
> +		ingpa = kvm_rdx_read(vcpu);
> +		outgpa = kvm_r8_read(vcpu);
> +	} else
> +#endif
> +	{
>  		param = ((u64)kvm_rdx_read(vcpu) << 32) |
>  			(kvm_rax_read(vcpu) & 0xffffffff);
>  		ingpa = ((u64)kvm_rbx_read(vcpu) << 32) |
> @@ -1615,13 +1620,6 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
>  		outgpa = ((u64)kvm_rdi_read(vcpu) << 32) |
>  			(kvm_rsi_read(vcpu) & 0xffffffff);
>  	}
> -#ifdef CONFIG_X86_64
> -	else {
> -		param = kvm_rcx_read(vcpu);
> -		ingpa = kvm_rdx_read(vcpu);
> -		outgpa = kvm_r8_read(vcpu);
> -	}
> -#endif
>  
>  	code = param & 0xffff;
>  	fast = !!(param & HV_HYPERCALL_FAST_BIT);
> 

Queued, thanks.

Paolo

Patch
diff mbox series

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index a39e38f13029..c10a8b10b203 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1594,7 +1594,7 @@  int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 {
 	u64 param, ingpa, outgpa, ret = HV_STATUS_SUCCESS;
 	uint16_t code, rep_idx, rep_cnt;
-	bool fast, longmode, rep;
+	bool fast, rep;
 
 	/*
 	 * hypercall generates UD from non zero cpl and real mode
@@ -1605,9 +1605,14 @@  int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 		return 1;
 	}
 
-	longmode = is_64_bit_mode(vcpu);
-
-	if (!longmode) {
+#ifdef CONFIG_X86_64
+	if (is_64_bit_mode(vcpu)) {
+		param = kvm_rcx_read(vcpu);
+		ingpa = kvm_rdx_read(vcpu);
+		outgpa = kvm_r8_read(vcpu);
+	} else
+#endif
+	{
 		param = ((u64)kvm_rdx_read(vcpu) << 32) |
 			(kvm_rax_read(vcpu) & 0xffffffff);
 		ingpa = ((u64)kvm_rbx_read(vcpu) << 32) |
@@ -1615,13 +1620,6 @@  int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 		outgpa = ((u64)kvm_rdi_read(vcpu) << 32) |
 			(kvm_rsi_read(vcpu) & 0xffffffff);
 	}
-#ifdef CONFIG_X86_64
-	else {
-		param = kvm_rcx_read(vcpu);
-		ingpa = kvm_rdx_read(vcpu);
-		outgpa = kvm_r8_read(vcpu);
-	}
-#endif
 
 	code = param & 0xffff;
 	fast = !!(param & HV_HYPERCALL_FAST_BIT);