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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [RFC v1 13/15] Update Posted-Interrupts Descriptor during vCPU scheduling
> -----Original Message-----
> From: Tian, Kevin
> Sent: Thursday, April 02, 2015 2:25 PM
> To: Wu, Feng; xen-devel@xxxxxxxxxxxxx
> Cc: JBeulich@xxxxxxxx; keir@xxxxxxx; Zhang, Yang Z
> Subject: RE: [RFC v1 13/15] Update Posted-Interrupts Descriptor during vCPU
> scheduling
>
> > From: Wu, Feng
> > Sent: Wednesday, March 25, 2015 8:32 PM
> >
> > The basic idea here is:
> > 1. When vCPU's state is RUNSTATE_running,
> > - set 'NV' to 'Notification Vector'.
> > - Clear 'SN' to accpet PI.
> > - set 'NDST' to the right pCPU.
> > 2. When vCPU's state is RUNSTATE_blocked,
> > - set 'NV' to 'Wake-up Vector', so we can wake up the
> > related vCPU when posted-interrupt happens for it.
> > - Clear 'SN' to accpet PI.
> > 3. When vCPU's state is RUNSTATE_runnable/RUNSTATE_offline,
> > - Set 'SN' to suppress non-urgent interrupts.
> > (Current, we only support non-urgent interrupts)
> > - Set 'NV' back to 'Notification Vector' if needed.
> >
> > Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
> > ---
> > xen/arch/x86/hvm/vmx/vmx.c | 108
> > +++++++++++++++++++++++++++++++++++++++++++++
> > xen/common/schedule.c | 3 ++
> > 2 files changed, 111 insertions(+)
> >
> > diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> > index b30392c..6323bd6 100644
> > --- a/xen/arch/x86/hvm/vmx/vmx.c
> > +++ b/xen/arch/x86/hvm/vmx/vmx.c
> > @@ -1710,6 +1710,113 @@ static void vmx_handle_eoi(u8 vector)
> > __vmwrite(GUEST_INTR_STATUS, status);
> > }
> >
> > +static void vmx_pi_desc_update(struct vcpu *v, int new_state)
> > +{
> > + struct pi_desc *pi_desc = &v->arch.hvm_vmx.pi_desc;
> > + struct pi_desc old, new;
> > + int old_state = v->runstate.state;
> > + unsigned long flags;
> > +
> > + if ( !iommu_intpost )
> > + return;
> > +
> > + switch ( new_state )
> > + {
> > + case RUNSTATE_runnable:
> > + case RUNSTATE_offline:
> > + /*
> > + * We don't need to send notification event to a non-running
> > + * vcpu, the interrupt information will be delivered to it before
> > + * VM-ENTRY when the vcpu is scheduled to run next time.
> > + */
> > + pi_set_sn(pi_desc);
> > +
> > + /*
> > + * If the state is transferred from RUNSTATE_blocked,
> > + * we should set 'NV' feild back to posted_intr_vector,
> > + * so the Posted-Interrupts can be delivered to the vCPU
> > + * by VT-d HW after it is scheduled to run.
> > + */
> > + if ( old_state == RUNSTATE_blocked )
> > + {
> > + do
> > + {
> > + old.control = new.control = pi_desc->control;
> > + new.nv = posted_intr_vector;
> > + }
> > + while ( cmpxchg(&pi_desc->control, old.control, new.control)
> > + != old.control );
> > +
> > + /*
> > + * Delete the vCPU from the related wakeup queue
> > + * if we are resuming from blocked state
> > + */
> > + spin_lock_irqsave(&per_cpu(blocked_vcpu_on_cpu_lock,
> > + v->processor), flags);
> > + list_del(&v->blocked_vcpu_list);
> > + spin_unlock_irqrestore(&per_cpu(blocked_vcpu_on_cpu_lock,
> > + v->processor), flags);
> > + }
> > + break;
> > +
> > + case RUNSTATE_blocked:
> > + /*
> > + * The vCPU is blocked on the wait queue.
> > + * Store the blocked vCPU on the list of the
> > + * vcpu->wakeup_cpu, which is the destination
> > + * of the wake-up notification event.
> > + */
> > + spin_lock_irqsave(&per_cpu(blocked_vcpu_on_cpu_lock,
> > + v->processor), flags);
> > + list_add_tail(&v->blocked_vcpu_list,
> > + &per_cpu(blocked_vcpu_on_cpu, v->processor));
> > + spin_unlock_irqrestore(&per_cpu(blocked_vcpu_on_cpu_lock,
> > + v->processor), flags);
> > +
> > + do
> > + {
> > + old.control = new.control = pi_desc->control;
> > +
> > + /*
> > + * We should not block the vCPU if
> > + * an interrupt is posted for it.
> > + */
> > +
> > + if ( pi_test_on(&old) == 1 )
> > + {
> > + tasklet_schedule(&v->vcpu_wakeup_tasklet);
> > + return;
> > + }
>
> so you also need to remove the vcpu from the blocked list, right?
Yes, I need to remove the vcpu here. I thought it could be removed in
another place in this patch, however, I feel it cannot do it after
more thinking about it. I think we can fix this issue in the following two ways:
#1) Just add the remove logic here.
or
#2) In function vcpu_runstate_change(), call 'hvm_funcs.pi_desc_update()' after
v->runstate.state = new_state; and pass the old_state to
'hvm_funcs.pi_desc_update()'.
then here is the code path:
tasklet_schedule(&v->vcpu_wakeup_tasklet) -> vcpu_unblock() -> vcpu_wake() ->
vcpu_runstate_change(v, RUNSTATE_runnable, NOW()) -> vmx_pi_desc_update()
So, the vCPU will be removed in 'case RUNSTATE_runnable:' of function
vmx_pi_desc_update().
>
> and how do you handle ON is set after above check? looks this is better
> handled behind cmpxchg loop...
- If 'ON' is set before 'if ( pi_test_on(&old) == 1 )', return
- If 'ON' is not set before it, and is set after it, '
cmpxchg(&pi_desc->control, old.control, new.control) != old.control ' returns
ture,
so, we will do the while again, at this time, 'if ( pi_test_on(&old) == 1 )' is
true.
Thanks,
Feng
>
> > +
> > + pi_clear_sn(&new);
> > + new.nv = pi_wakeup_vector;
> > + }
> > + while ( cmpxchg(&pi_desc->control, old.control, new.control)
> > + != old.control );
> > + break;
> > +
> > + case RUNSTATE_running:
> > + ASSERT( pi_test_sn(pi_desc) == 1 );
> > +
> > + do
> > + {
> > + old.control = new.control = pi_desc->control;
> > + if ( x2apic_enabled )
> > + new.ndst = cpu_physical_id(v->processor);
> > + else
> > + new.ndst = (cpu_physical_id(v->processor) << 8) &
> > 0xFF00;
> > +
> > + pi_clear_sn(&new);
> > + }
> > + while ( cmpxchg(&pi_desc->control, old.control, new.control)
> > + != old.control );
> > + break;
> > +
> > + default:
> > + break;
> > + }
> > +}
> > +
> > void vmx_hypervisor_cpuid_leaf(uint32_t sub_idx,
> > uint32_t *eax, uint32_t *ebx,
> > uint32_t *ecx, uint32_t *edx)
> > @@ -1795,6 +1902,7 @@ static struct hvm_function_table __initdata
> > vmx_function_table = {
> > .process_isr = vmx_process_isr,
> > .deliver_posted_intr = vmx_deliver_posted_intr,
> > .sync_pir_to_irr = vmx_sync_pir_to_irr,
> > + .pi_desc_update = vmx_pi_desc_update,
> > .handle_eoi = vmx_handle_eoi,
> > .nhvm_hap_walk_L1_p2m = nvmx_hap_walk_L1_p2m,
> > .hypervisor_cpuid_leaf = vmx_hypervisor_cpuid_leaf,
> > diff --git a/xen/common/schedule.c b/xen/common/schedule.c
> > index ef79847..acf3186 100644
> > --- a/xen/common/schedule.c
> > +++ b/xen/common/schedule.c
> > @@ -157,6 +157,9 @@ static inline void vcpu_runstate_change(
> > v->runstate.state_entry_time = new_entry_time;
> > }
> >
> > + if ( is_hvm_vcpu(v) && hvm_funcs.pi_desc_update )
> > + hvm_funcs.pi_desc_update(v, new_state);
> > +
> > v->runstate.state = new_state;
> > }
> >
> > --
> > 2.1.0
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