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SubjectRe: [PATCH] x86/vmware: use unsigned integer for shifting
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Hi Shreenidhi,

Thank you for the patch!

On 5/20/22 2:26 AM, Borislav Petkov wrote:
> On Fri, May 20, 2022 at 12:58:57PM +0530, Shreenidhi Shedi wrote:
>> Shifting signed 32-bit value by 31 bits is implementation-defined
>> behaviour. Using unsigned is better option for this.
>>

Can you also add a "Fixes:" tag with the commit that introduced the
issue? I believe it is 4cca6ea04d31 ("x86/apic: Allow x2apic without
IR on VMware platform").

>> Signed-off-by: Shreenidhi Shedi <sshedi@vmware.com>
>> ---
>> arch/x86/kernel/cpu/vmware.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
>> index c04b933f48d3..b28f789d3c56 100644
>> --- a/arch/x86/kernel/cpu/vmware.c
>> +++ b/arch/x86/kernel/cpu/vmware.c
>> @@ -476,7 +476,7 @@ 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 &&
>> + return (eax & (1U << VMWARE_CMD_VCPU_RESERVED)) == 0 &&
>> (eax & (1 << VMWARE_CMD_LEGACY_X2APIC)) != 0;
>
> Or you can use the BIT() macro and simplify this expression even more:
>
> return !(eax & BIT(VMWARE_CMD_VCPU_RESERVED)) &&
> (eax & BIT(VMWARE_CMD_LEGACY_X2APIC));
>
>

That's better indeed.

Regards,
Srivatsa

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