Re: [RFC PATCH v1] x86/split_lock: Provide KVM helper to log guest bus lock exits

Manali Shukla
2026-04-08T05:09:39Z

On 3/31/2026 11:04 PM, Sean Christopherson wrote:
> On Tue, Mar 24, 2026, Manali Shukla wrote:
>> The intent is purely observational — give hypervisor owners
>> visibility into which guest is generating bus locks so they can act
>> accordingly. No policy enforcement is done in the kernel. Suggestions
>> on the approach are welcome.
>
> This makes no sense. KVM is exiting to userspace, the hypervisor owner doesn't
> need to grep dmesg to understand *exactly* what vCPU is generating bus locks.

I agree that the VMM receives KVM_EXIT_X86_BUS_LOCK and knows which vCPU
caused it, and I am fine with that approach. However, this request came
from a customer who wanted to know which guest is causing bus locks at
which RIP in dmesg, similar to how split lock detection on Intel does
it. I am trying to address that use case.

-Manali