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

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Date:   Fri, 20 May 2022 13:52:02 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Shreenidhi Shedi <yesshedi@...il.com>
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 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.

> ---
>  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