On 2/13/2025 11:17 PM, Sean Christopherson wrote:
On Thu, Feb 13, 2025, Binbin Wu wrote:
On 2/13/2025 11:23 AM, Binbin Wu wrote:
On 2/13/2025 2:56 AM, Sean Christopherson wrote:
On Wed, Feb 12, 2025, Binbin Wu wrote:
On 2/12/2025 8:46 AM, Sean Christopherson wrote:
I am completely comfortable saying that KVM doesn't care about STI/SS shadows
outside of the HALTED case, and so unless I'm missing something, I think it makes
sense for tdx_protected_apic_has_interrupt() to not check RVI outside of the HALTED
case, because it's impossible to know if the interrupt is actually unmasked, and
statistically it's far, far more likely that it _is_ masked.
OK. Will update tdx_protected_apic_has_interrupt() in "TDX interrupts" part.
And use kvm_vcpu_has_events() to replace the open code in this patch.
Something to keep an eye on: kvm_vcpu_has_events() returns true if pv_unhalted
is set, and pv_unhalted is only cleared on transitions KVM_MP_STATE_RUNNABLE.
If the guest initiates a spurious wakeup, pv_unhalted could be left set in
perpetuity.
Oh, yes.
KVM_HC_KICK_CPU is allowed in TDX guests.
And a clever guest can send a REMRD IPI.
The change below looks good to me.
One minor issue is when guest initiates a spurious wakeup, pv_unhalted is
left set, then later when the guest want to halt the vcpu, in
__kvm_emulate_halt(), since pv_unhalted is still set and the state will not
transit to KVM_MP_STATE_HALTED.
But I guess it's guests' responsibility to not initiate spurious wakeup,
guests need to bear the fact that HLT could fail due to a previous
spurious wakeup?
Just found a patch set for fixing the issue.
FWIW, Jim's series doesn't address spurious wakeups per se, it just ensures
pv_unhalted is cleared when transitioning to RUNNING. If the vCPU is already
RUNNING, __apic_accept_irq() will set pv_unhalted and nothing will clear it
until the next transition to RUNNING (which implies at least an attempted
transition away from RUNNING).
Indeed.
I am wondering why KVM doesn't clear pv_unhalted before the vcpu entering guest?
Is the additional memory access a concern or is there some other reason?
