2022-05-22 09:55:09

by Srivatsa S. Bhat

[permalink] [raw]
Subject: Re: [PATCH v2] x86/vmware: use unsigned integer for shifting

On 5/20/22 7:09 AM, Shreenidhi Shedi wrote:
> From: Shreenidhi Shedi <[email protected]>
>
> From: Shreenidhi Shedi <[email protected]>
>
> 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 <[email protected]>
> ---
> 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..cd809c5b17f0 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)) &&
> + (eax & BIT(VMWARE_CMD_LEGACY_X2APIC))


This patch has clearly not been tested, and not even compiled! (It is
missing a semicolon at the end of the return statement).

Please take your time to revise and test your patch based on the
review feedback; there is no hurry! :)

(Also, while at it, the double From: at the beginning of the patch
needs to be fixed too).

Regards,
Srivatsa