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

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Date:   Fri, 20 May 2022 19:33:30 +0530
From:   Shreenidhi Shedi <yesshedi@...il.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     srivatsa@...il.mit.edu, amakhalov@...are.com, tglx@...utronix.de,
        mingo@...hat.com, dave.hansen@...ux.intel.com, hpa@...or.com,
        virtualization@...ts.linux-foundation.org, pv-drivers@...are.com,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        Shreenidhi Shedi <sshedi@...are.com>
Subject: Re: [PATCH v1] x86/vmware: use unsigned integer for shifting

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@...are.com>
>> Signed-off-by: Shreenidhi Shedi <yesshedi@...il.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 :(