From 93fb0b10e7121f3be86c4cdd564d7e1c0974deca Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Fri, 31 Jan 2025 17:38:23 -0800 Subject: [PATCH] KVM: x86: Set PVCLOCK_GUEST_STOPPED only for kvmclock, not for Xen PV clock Handle "guest stopped" propagation only for kvmclock, as the flag is set if and only if kvmclock is "active", i.e. can only be set for Xen PV clock if kvmclock *and* Xen PV clock are in-use by the guest, which creates very bizarre behavior for the guest. Simply restrict the flag to kvmclock, e.g. instead of trying to handle Xen PV clock, as propagation of PVCLOCK_GUEST_STOPPED was unintentionally added during a refactoring, and while Xen proper defines XEN_PVCLOCK_GUEST_STOPPED, there's no evidence that Xen guests actually support the flag. Check and clear pvclock_set_guest_stopped_request if and only if kvmclock is active to preserve the original behavior, i.e. keep the flag pending if kvmclock happens to be disabled when KVM processes the initial request. Fixes: aa096aa0a05f ("KVM: x86/xen: setup pvclock updates") Cc: Paul Durrant Cc: David Woodhouse Reviewed-by: Paul Durrant Link: https://lore.kernel.org/r/20250201013827.680235-8-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 906c60cc811a..8fd5922f22a6 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3262,20 +3262,21 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) if (use_master_clock) vcpu->hv_clock.flags |= PVCLOCK_TSC_STABLE_BIT; - if (vcpu->pv_time.active -#ifdef CONFIG_KVM_XEN - || vcpu->xen.vcpu_info_cache.active - || vcpu->xen.vcpu_time_info_cache.active -#endif - ) { + if (vcpu->pv_time.active) { + /* + * GUEST_STOPPED is only supported by kvmclock, and KVM's + * historic behavior is to only process the request if kvmclock + * is active/enabled. + */ if (vcpu->pvclock_set_guest_stopped_request) { vcpu->hv_clock.flags |= PVCLOCK_GUEST_STOPPED; vcpu->pvclock_set_guest_stopped_request = false; } + kvm_setup_guest_pvclock(v, &vcpu->pv_time, 0, false); + + vcpu->hv_clock.flags &= ~PVCLOCK_GUEST_STOPPED; } - if (vcpu->pv_time.active) - kvm_setup_guest_pvclock(v, &vcpu->pv_time, 0, false); #ifdef CONFIG_KVM_XEN if (vcpu->xen.vcpu_info_cache.active) kvm_setup_guest_pvclock(v, &vcpu->xen.vcpu_info_cache, -- 2.50.1