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Date: Mon, 14 Sep 2015 07:57:00 +0000
From: "Wu, Feng" <feng.wu@...el.com>
To: Paolo Bonzini <pbonzini@...hat.com>,
"alex.williamson@...hat.com" <alex.williamson@...hat.com>,
"joro@...tes.org" <joro@...tes.org>,
"mtosatti@...hat.com" <mtosatti@...hat.com>
CC: "eric.auger@...aro.org" <eric.auger@...aro.org>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Wu, Feng" <feng.wu@...el.com>
Subject: RE: [PATCH v7 15/17] KVM: Update Posted-Interrupts Descriptor when
vCPU is blocked
First of all, Paolo, thanks a lot for your review on this series, it really means a lot!:)
> -----Original Message-----
> From: linux-kernel-owner@...r.kernel.org
> [mailto:linux-kernel-owner@...r.kernel.org] On Behalf Of Paolo Bonzini
> Sent: Friday, September 11, 2015 7:21 PM
> To: Wu, Feng; alex.williamson@...hat.com; joro@...tes.org;
> mtosatti@...hat.com
> Cc: eric.auger@...aro.org; kvm@...r.kernel.org;
> iommu@...ts.linux-foundation.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v7 15/17] KVM: Update Posted-Interrupts Descriptor when
> vCPU is blocked
>
>
>
> On 25/08/2015 10:50, Feng Wu wrote:
> > This patch updates the Posted-Interrupts Descriptor when vCPU
> > is blocked.
> >
> > pre-block:
> > - Add the vCPU to the blocked per-CPU list
> > - Set 'NV' to POSTED_INTR_WAKEUP_VECTOR
> >
> > post-block:
> > - Remove the vCPU from the per-CPU list
> >
> > Signed-off-by: Feng Wu <feng.wu@...el.com>
> > ---
> > arch/x86/include/asm/kvm_host.h | 5 ++
> > arch/x86/kvm/vmx.c | 151
> ++++++++++++++++++++++++++++++++++++++++
> > arch/x86/kvm/x86.c | 55 ++++++++++++---
> > include/linux/kvm_host.h | 3 +
> > virt/kvm/kvm_main.c | 3 +
> > 5 files changed, 207 insertions(+), 10 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h
> b/arch/x86/include/asm/kvm_host.h
> > index 22269b4..32af275 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -554,6 +554,8 @@ struct kvm_vcpu_arch {
> > */
> > bool write_fault_to_shadow_pgtable;
> >
> > + bool halted;
> > +
> > /* set at EPT violation at this point */
> > unsigned long exit_qualification;
> >
> > @@ -868,6 +870,9 @@ struct kvm_x86_ops {
> >
> > void (*pi_clear_sn)(struct kvm_vcpu *vcpu);
> > void (*pi_set_sn)(struct kvm_vcpu *vcpu);
> > +
> > + int (*pi_pre_block)(struct kvm_vcpu *vcpu);
> > + void (*pi_post_block)(struct kvm_vcpu *vcpu);
>
> Just pre_block/post_block please. Also, please document the return
> value of pre_block.
>
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index ef93fdc..fc7f222 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -5869,7 +5869,13 @@ int kvm_vcpu_halt(struct kvm_vcpu *vcpu)
> > {
> > ++vcpu->stat.halt_exits;
> > if (irqchip_in_kernel(vcpu->kvm)) {
> > - vcpu->arch.mp_state = KVM_MP_STATE_HALTED;
> > + /* Handle posted-interrupt when vCPU is to be halted */
> > + if (!kvm_x86_ops->pi_pre_block ||
> > + (kvm_x86_ops->pi_pre_block &&
>
> No need to test kvm_x86_ops->pi_pre_block again.
>
> > + kvm_x86_ops->pi_pre_block(vcpu) == 0)) {
> > + vcpu->arch.halted = true;
> > + vcpu->arch.mp_state = KVM_MP_STATE_HALTED;
> > + }
> > return 1;
> > } else {
> > vcpu->run->exit_reason = KVM_EXIT_HLT;
> > @@ -6518,6 +6524,21 @@ static int vcpu_enter_guest(struct kvm_vcpu
> *vcpu)
> > kvm_vcpu_reload_apic_access_page(vcpu);
> > }
> >
> > + /*
> > + * Since posted-interrupts can be set by VT-d HW now, in this
> > + * case, KVM_REQ_EVENT is not set. We move the following
> > + * operations out of the if statement.
> > + */
>
> Just "KVM_REQ_EVENT is not set when posted interrupts are set by VT-d
> hardware, so we have to update RVI unconditionally", please.
>
> Could we skip this (in a future patch) if PI.ON=0?
Do you mean only executing the following code when PI.ON == 1?
Maybe we cannot do that, since 'ON' can be cleared by hypervisor
in lots of places.
>
> > + if (kvm_lapic_enabled(vcpu)) {
> > + /*
> > + * Update architecture specific hints for APIC
> > + * virtual interrupt delivery.
> > + */
> > + if (kvm_x86_ops->hwapic_irr_update)
> > + kvm_x86_ops->hwapic_irr_update(vcpu,
> > + kvm_lapic_find_highest_irr(vcpu));
> > + }
> > +
> > if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {
> > kvm_apic_accept_events(vcpu);
> > if (vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) {
> > @@ -6534,13 +6555,6 @@ static int vcpu_enter_guest(struct kvm_vcpu
> *vcpu)
> > kvm_x86_ops->enable_irq_window(vcpu);
> >
> > if (kvm_lapic_enabled(vcpu)) {
> > - /*
> > - * Update architecture specific hints for APIC
> > - * virtual interrupt delivery.
> > - */
> > - if (kvm_x86_ops->hwapic_irr_update)
> > - kvm_x86_ops->hwapic_irr_update(vcpu,
> > - kvm_lapic_find_highest_irr(vcpu));
> > update_cr8_intercept(vcpu);
> > kvm_lapic_sync_to_vapic(vcpu);
> > }
> > @@ -6711,10 +6725,31 @@ static int vcpu_run(struct kvm_vcpu *vcpu)
> >
> > for (;;) {
> > if (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&
> > - !vcpu->arch.apf.halted)
> > + !vcpu->arch.apf.halted) {
> > + /*
> > + * For some cases, we can get here with
> > + * vcpu->arch.halted being true.
> > + */
>
> Which cases?
See the following scenario:
vcpu_run()
{
......
vcpu_enter_guest() --> VM_EXIT -> kvm_vcpu_halt() --> vcpu->arch.halted = true;
........
kvm_check_async_pf_completion()
--> ...... --> kvm_arch_async_page_present(), in which it set
vcpu->arch.apf.halted to false and vcpu->arch.mp_state
to KVM_MP_STATE_RUNNABLE, then next time we re-enter
the for (;;) loop, it will end up vcpu->arch.halted being true
}
Thanks,
Feng
>
> Paolo
>
> > + if (kvm_x86_ops->pi_post_block && vcpu->arch.halted) {
> > + kvm_x86_ops->pi_post_block(vcpu);
> > + vcpu->arch.halted = false;
> > + }
> > +
> > r = vcpu_enter_guest(vcpu);
> > - else
> > + } else {
> > r = vcpu_block(kvm, vcpu);
> > +
> > + /*
> > + * pi_post_block() must be called after
> > + * pi_pre_block() which is called in
> > + * kvm_vcpu_halt().
> > + */
> > + if (kvm_x86_ops->pi_post_block && vcpu->arch.halted) {
> > + kvm_x86_ops->pi_post_block(vcpu);
> > + vcpu->arch.halted = false;
> > + }
> > + }
> > +
> > if (r <= 0)
> > break;
> >
> > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> > index f4005dc..6aa69f4 100644
> > --- a/include/linux/kvm_host.h
> > +++ b/include/linux/kvm_host.h
> > @@ -233,6 +233,9 @@ struct kvm_vcpu {
> > unsigned long requests;
> > unsigned long guest_debug;
> >
> > + int pre_pcpu;
> > + struct list_head blocked_vcpu_list;
> > +
> > struct mutex mutex;
> > struct kvm_run *run;
> >
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index 8b8a444..191c7eb 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -220,6 +220,9 @@ int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm
> *kvm, unsigned id)
> > init_waitqueue_head(&vcpu->wq);
> > kvm_async_pf_vcpu_init(vcpu);
> >
> > + vcpu->pre_pcpu = -1;
> > + INIT_LIST_HEAD(&vcpu->blocked_vcpu_list);
> > +
> > page = alloc_page(GFP_KERNEL | __GFP_ZERO);
> > if (!page) {
> > r = -ENOMEM;
> >
> --
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