arch/x86/kernel/cpu/vmware.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
From: Shreenidhi Shedi <sshedi@vmware.com>
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")
Cc: stable@vger.kernel.org
Signed-off-by: Shreenidhi Shedi <sshedi@vmware.com>
---
arch/x86/kernel/cpu/vmware.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index c04b933f4..02039ec35 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -476,8 +476,8 @@ 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));
}
#ifdef CONFIG_AMD_MEM_ENCRYPT
--
2.36.1
On Fri, May 27, 2022 at 11:27:37PM +0530, Shreenidhi Shedi wrote: > From: Shreenidhi Shedi <sshedi@vmware.com> > > Shifting signed 32-bit value by 31 bits is implementation-defined > behaviour. Using unsigned is better option for this. The kernel builds with -fno-strict-overflow and as such this behaviour is well defined. > Fixes: 4cca6ea04d31 ("x86/apic: Allow x2apic without IR on VMware platform") Nothing broken, therefore nothing fixed.
On 5/28/22 6:52 AM, Peter Zijlstra wrote: > On Fri, May 27, 2022 at 11:27:37PM +0530, Shreenidhi Shedi wrote: >> From: Shreenidhi Shedi <sshedi@vmware.com> >> >> Shifting signed 32-bit value by 31 bits is implementation-defined >> behaviour. Using unsigned is better option for this. > > The kernel builds with -fno-strict-overflow and as such this behaviour > is well defined. > Ah, I see. Thank you, Peter! >> Fixes: 4cca6ea04d31 ("x86/apic: Allow x2apic without IR on VMware platform") > > Nothing broken, therefore nothing fixed. > Agreed. I think using the BIT() macro still provides a nice readability improvement. So, Shreenidhi, could you spin a new version of the patch with the same code changes but with a different commit message about using the BIT() macro to simplify the code, and also include a clarification as to why the existing code is correct (which Peter pointed out), please? Thank you! Regards, Srivatsa VMware Photon OS
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