On Thu, 2021-10-28 at 14:28 +0300, Maxim Levitsky wrote:
> On Fri, 2021-10-08 at 19:12 -0700, Sean Christopherson wrote:
> > Hoist the CPU => APIC ID conversion for the Posted Interrupt descriptor
> > out of the loop to write the descriptor, preemption is disabled so the
> > CPU won't change, and if the APIC ID changes KVM has bigger problems.
> >
> > No functional change intended.
>
> Is preemption always disabled in vmx_vcpu_pi_load? vmx_vcpu_pi_load is called from vmx_vcpu_load,
> which is called indirectly from vcpu_load which is called from many ioctls,
> which userspace does. In these places I don't think that preemption is disabled.
You can disregard this, I missed the fact that we have 'int cpu = get_cpu();'
which disables preemption in 'vcpu_load'
Thus,
Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Best regards,
Maxim Levitsky
>
> Best regards,
> Maxim Levitsky
>
> > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> > ---
> > arch/x86/kvm/vmx/posted_intr.c | 25 +++++++++++--------------
> > 1 file changed, 11 insertions(+), 14 deletions(-)
> >
> > diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
> > index fea343dcc011..2b2206339174 100644
> > --- a/arch/x86/kvm/vmx/posted_intr.c
> > +++ b/arch/x86/kvm/vmx/posted_intr.c
> > @@ -51,17 +51,15 @@ void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu)
> > goto after_clear_sn;
> > }
> >
> > - /* The full case. */
> > + /* The full case. Set the new destination and clear SN. */
> > + dest = cpu_physical_id(cpu);
> > + if (!x2apic_mode)
> > + dest = (dest << 8) & 0xFF00;
> > +
> > do {
> > old.control = new.control = READ_ONCE(pi_desc->control);
> >
> > - dest = cpu_physical_id(cpu);
> > -
> > - if (x2apic_mode)
> > - new.ndst = dest;
> > - else
> > - new.ndst = (dest << 8) & 0xFF00;
> > -
> > + new.ndst = dest;
> > new.sn = 0;
> > } while (cmpxchg64(&pi_desc->control, old.control,
> > new.control) != old.control);
> > @@ -103,15 +101,14 @@ static void __pi_post_block(struct kvm_vcpu *vcpu)
> > WARN(pi_desc->nv != POSTED_INTR_WAKEUP_VECTOR,
> > "Wakeup handler not enabled while the vCPU was blocking");
> >
> > + dest = cpu_physical_id(vcpu->cpu);
> > + if (!x2apic_mode)
> > + dest = (dest << 8) & 0xFF00;
> > +
> > do {
> > old.control = new.control = READ_ONCE(pi_desc->control);
> >
> > - dest = cpu_physical_id(vcpu->cpu);
> > -
> > - if (x2apic_mode)
> > - new.ndst = dest;
> > - else
> > - new.ndst = (dest << 8) & 0xFF00;
> > + new.ndst = dest;
> >
> > /* set 'NV' to 'notification vector' */
> > new.nv = POSTED_INTR_VECTOR;
