Allow userspace to set a vCPU's mp_state to INIT_RECEIVED in conjunction
with a pending SMI, as rejecting that combination could result in KVM
disallowing reflecting the output from KVM_GET_VCPU_EVENTS back into KVM
via KVM_SET_VCPU_EVENTS.
At the time the check was added, smi_pending could only be set in the
context of KVM_RUN, with the vCPU in the RUNNABLE state. I.e. it was
impossible for KVM to save vCPU state such that userspace could see a
pending SMI for a vCPU in WFS.
That no longer holds true now that KVM processes requested SMIs during
KVM_GET_VCPU_EVENTS, e.g. if a vCPU receives an SMI while in WFS, and
then userspace saves vCPU state.
Note, this may partially re-open the user-triggerable WARN that was mostly
closed by commit 28bf28887976 ("KVM: x86: fix user triggerable warning in
kvm_apic_accept_events()"), but that WARN can already be triggered in
several other ways, e.g. if userspace stuffs VMXON=1 after putting the
vCPU into WFS. That issue will be addressed in an upcoming commit, in a
more robust fashion (hopefully).
Fixes: 1f7becf1b7e2 ("KVM: x86: get smi pending status correctly")
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/kvm/x86.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index dd34a2ec854c..7e3ab297a1bf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11895,10 +11895,9 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
/*
* Pending INITs are reported using KVM_SET_VCPU_EVENTS, disallow
* forcing the guest into INIT/SIPI if those events are supposed to be
- * blocked. KVM prioritizes SMI over INIT, so reject INIT/SIPI state
- * if an SMI is pending as well.
+ * blocked.
*/
- if ((!kvm_apic_init_sipi_allowed(vcpu) || vcpu->arch.smi_pending) &&
+ if (!kvm_apic_init_sipi_allowed(vcpu) &&
(mp_state->mp_state == KVM_MP_STATE_SIPI_RECEIVED ||
mp_state->mp_state == KVM_MP_STATE_INIT_RECEIVED))
goto out;
--
2.50.0.rc0.604.gd4ff7b7c86-goog
