* [PATCH] x86/vmware: use unsigned integer for shifting
@ 2022-05-20 7:28 Shreenidhi Shedi
2022-05-20 9:26 ` Borislav Petkov
0 siblings, 1 reply; 4+ messages in thread
From: Shreenidhi Shedi @ 2022-05-20 7:28 UTC (permalink / raw)
To: srivatsa, amakhalov, tglx, mingo, bp, dave.hansen, hpa
Cc: virtualization, pv-drivers, x86, linux-kernel, yesshedi,
Shreenidhi Shedi
Shifting signed 32-bit value by 31 bits is implementation-defined
behaviour. Using unsigned is better option for this.
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;
}
--
2.36.1
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] x86/vmware: use unsigned integer for shifting
2022-05-20 7:28 [PATCH] x86/vmware: use unsigned integer for shifting Shreenidhi Shedi
@ 2022-05-20 9:26 ` Borislav Petkov
2022-05-20 11:29 ` Srivatsa S. Bhat
0 siblings, 1 reply; 4+ messages in thread
From: Borislav Petkov @ 2022-05-20 9:26 UTC (permalink / raw)
To: Shreenidhi Shedi
Cc: srivatsa, amakhalov, tglx, mingo, dave.hansen, hpa,
virtualization, pv-drivers, x86, linux-kernel, Shreenidhi Shedi
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.
>
> 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));
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] x86/vmware: use unsigned integer for shifting
2022-05-20 9:26 ` Borislav Petkov
@ 2022-05-20 11:29 ` Srivatsa S. Bhat
2022-05-20 11:42 ` Shreenidhi Shedi
0 siblings, 1 reply; 4+ messages in thread
From: Srivatsa S. Bhat @ 2022-05-20 11:29 UTC (permalink / raw)
To: Borislav Petkov, Shreenidhi Shedi
Cc: amakhalov, tglx, mingo, dave.hansen, hpa, virtualization,
pv-drivers, x86, linux-kernel, Shreenidhi Shedi
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
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] x86/vmware: use unsigned integer for shifting
2022-05-20 11:29 ` Srivatsa S. Bhat
@ 2022-05-20 11:42 ` Shreenidhi Shedi
0 siblings, 0 replies; 4+ messages in thread
From: Shreenidhi Shedi @ 2022-05-20 11:42 UTC (permalink / raw)
To: Srivatsa S. Bhat, Borislav Petkov
Cc: amakhalov, tglx, mingo, dave.hansen, hpa, virtualization,
pv-drivers, x86, linux-kernel, Shreenidhi Shedi
On 20/05/22 4:59 pm, Srivatsa S. Bhat wrote:
> 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
Thanks for the quick reviews Boris and Srivatsa. I will make the changes and push the another patch soon.
--
Shedi
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-05-20 11:43 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-05-20 7:28 [PATCH] x86/vmware: use unsigned integer for shifting Shreenidhi Shedi
2022-05-20 9:26 ` Borislav Petkov
2022-05-20 11:29 ` Srivatsa S. Bhat
2022-05-20 11:42 ` Shreenidhi Shedi
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox