Hi Sean, On 6/4/2024 6:15 AM, Sean Christopherson wrote: > On Mon, Apr 29, 2024, Ravi Bangoria wrote: >> Upcoming AMD uarch will support Bus Lock Detect. Add support for it >> in KVM. Bus Lock Detect is enabled through MSR_IA32_DEBUGCTLMSR and >> MSR_IA32_DEBUGCTLMSR is virtualized only if LBR Virtualization is >> enabled. Add this dependency in the KVM. > > This is woefully incomplete, e.g. db_interception() needs to be updated to decipher > whether the #DB is the responsbility of the host or of the guest. Can you please elaborate. Are you referring to vcpu->guest_debug thingy? > Honestly, I don't see any point in virtualizing this in KVM. As Jim alluded to, > what's far, far more interesting for KVM is "Bus Lock Threshold". Virtualizing > this for the guest would have been nice to have during the initial split-lock #AC > support, but now I'm skeptical the complexity is worth the payoff. This has a valid usecase of penalizing offending processes. I'm not sure how much it's really used in the production though. > I suppose we could allow it if #DB isn't interecepted, at which point the enabling > required is minimal? The feature uses DEBUG_CTL MSR, #DB and DR6 register. Do you mean expose it when all three are accelerated or just #DB? Thanks for the feedback, Ravi
