[v1] x86/vmware: use unsigned integer for shifting

[PATCH v1] x86/vmware: use unsigned integer for shifting

Posted by Shreenidhi Shedi 3 years, 11 months ago

Shifting signed 32-bit value by 31 bits is implementation-defined
behaviour. Using unsigned is better option for this.

Fixes: 4cca6ea04d31 ("x86/apic: Allow x2apic without IR on VMware platform")

Signed-off-by: Shreenidhi Shedi <sshedi@vmware.com>
Signed-off-by: Shreenidhi Shedi <yesshedi@gmail.com>
---
 arch/x86/kernel/cpu/vmware.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index c04b933f48d3..7f44ea073436 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -28,6 +28,7 @@
 #include <linux/cpu.h>
 #include <linux/reboot.h>
 #include <linux/static_call.h>
+#include <linux/bits.h>
 #include <asm/div64.h>
 #include <asm/x86_init.h>
 #include <asm/hypervisor.h>
@@ -476,8 +477,8 @@ static bool __init vmware_legacy_x2apic_available(void)
 {
 	uint32_t eax, ebx, ecx, edx;
 	VMWARE_CMD(GETVCPU_INFO, eax, ebx, ecx, edx);
-	return (eax & (1 << VMWARE_CMD_VCPU_RESERVED)) == 0 &&
-	       (eax & (1 << VMWARE_CMD_LEGACY_X2APIC)) != 0;
+	return (eax & BIT(VMWARE_CMD_VCPU_RESERVED)) == 0 &&
+	       (eax & BIT(VMWARE_CMD_LEGACY_X2APIC)) != 0;
 }
 
 #ifdef CONFIG_AMD_MEM_ENCRYPT
-- 
2.36.1

Re: [PATCH v1] x86/vmware: use unsigned integer for shifting

Posted by Borislav Petkov 3 years, 11 months ago

On Fri, May 20, 2022 at 05:17:12PM +0530, Shreenidhi Shedi wrote:
> Shifting signed 32-bit value by 31 bits is implementation-defined
> behaviour. Using unsigned is better option for this.
> 
> Fixes: 4cca6ea04d31 ("x86/apic: Allow x2apic without IR on VMware platform")
> 
> Signed-off-by: Shreenidhi Shedi <sshedi@vmware.com>
> Signed-off-by: Shreenidhi Shedi <yesshedi@gmail.com>

This is not how this is done - you need to set your author email
properly in git so that it adds your From: ... @vmware.com> instead of
having two SOBs.

> ---
>  arch/x86/kernel/cpu/vmware.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
> index c04b933f48d3..7f44ea073436 100644
> --- a/arch/x86/kernel/cpu/vmware.c
> +++ b/arch/x86/kernel/cpu/vmware.c
> @@ -28,6 +28,7 @@
>  #include <linux/cpu.h>
>  #include <linux/reboot.h>
>  #include <linux/static_call.h>
> +#include <linux/bits.h>
>  #include <asm/div64.h>
>  #include <asm/x86_init.h>
>  #include <asm/hypervisor.h>
> @@ -476,8 +477,8 @@ static bool __init vmware_legacy_x2apic_available(void)
>  {
>  	uint32_t eax, ebx, ecx, edx;
>  	VMWARE_CMD(GETVCPU_INFO, eax, ebx, ecx, edx);
> -	return (eax & (1 << VMWARE_CMD_VCPU_RESERVED)) == 0 &&
> -	       (eax & (1 << VMWARE_CMD_LEGACY_X2APIC)) != 0;
> +	return (eax & BIT(VMWARE_CMD_VCPU_RESERVED)) == 0 &&
> +	       (eax & BIT(VMWARE_CMD_LEGACY_X2APIC)) != 0;
						    ^^^^^^^^

You did hurry too much with sending a new version.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH v1] x86/vmware: use unsigned integer for shifting

Posted by Shreenidhi Shedi 3 years, 11 months ago

On 20/05/22 5:22 pm, Borislav Petkov wrote:
> On Fri, May 20, 2022 at 05:17:12PM +0530, Shreenidhi Shedi wrote:
>> Shifting signed 32-bit value by 31 bits is implementation-defined
>> behaviour. Using unsigned is better option for this.
>>
>> Fixes: 4cca6ea04d31 ("x86/apic: Allow x2apic without IR on VMware platform")
>>
>> Signed-off-by: Shreenidhi Shedi <sshedi@vmware.com>
>> Signed-off-by: Shreenidhi Shedi <yesshedi@gmail.com>
> 
> This is not how this is done - you need to set your author email
> properly in git so that it adds your From: ... @vmware.com> instead of
> having two SOBs.
> 

I deliberately did it because I was lacking clarity on using my org mail & personal mail id.
Thanks Srivatsa for the help and making things clear on this.

>> ---
>>  arch/x86/kernel/cpu/vmware.c | 5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
>> index c04b933f48d3..7f44ea073436 100644
>> --- a/arch/x86/kernel/cpu/vmware.c
>> +++ b/arch/x86/kernel/cpu/vmware.c
>> @@ -28,6 +28,7 @@
>>  #include <linux/cpu.h>
>>  #include <linux/reboot.h>
>>  #include <linux/static_call.h>
>> +#include <linux/bits.h>
>>  #include <asm/div64.h>
>>  #include <asm/x86_init.h>
>>  #include <asm/hypervisor.h>
>> @@ -476,8 +477,8 @@ static bool __init vmware_legacy_x2apic_available(void)
>>  {
>>  	uint32_t eax, ebx, ecx, edx;
>>  	VMWARE_CMD(GETVCPU_INFO, eax, ebx, ecx, edx);
>> -	return (eax & (1 << VMWARE_CMD_VCPU_RESERVED)) == 0 &&
>> -	       (eax & (1 << VMWARE_CMD_LEGACY_X2APIC)) != 0;
>> +	return (eax & BIT(VMWARE_CMD_VCPU_RESERVED)) == 0 &&
>> +	       (eax & BIT(VMWARE_CMD_LEGACY_X2APIC)) != 0;
> 						    ^^^^^^^^
> 
> You did hurry too much with sending a new version.
> 

Oops :(

Re: [PATCH v1] x86/vmware: use unsigned integer for shifting

Posted by Borislav Petkov 3 years, 11 months ago

On Fri, May 20, 2022 at 07:33:30PM +0530, Shreenidhi Shedi wrote:
> I deliberately did it because I was lacking clarity on using my org
> mail & personal mail id.

You could have a look at Documentation/process/submitting-patches.rst
and everything under Documentation/process/ in case you don't know what
to do.

Using checkpatch.pl on your patch before submitting it, is also
something you should do.

HTH.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette