On 2013-03-04 22:41, Jan Kiszka wrote: > From: Jan Kiszka <[email protected]> > > A VCPU sending INIT or SIPI to some other VCPU races for setting the > remote VCPU's mp_state. When we were unlucky, KVM_MP_STATE_INIT_RECEIVED > was overwritten by kvm_emulate_halt and, thus, got lost. > > Fix this by raising requests on the sender side that will then be > handled synchronously over the target VCPU context. > > Signed-off-by: Jan Kiszka <[email protected]> > --- > > Changes in v2: > - check transition to INIT_RECEIVED in vcpu_enter_guest > - removed return value of kvm_check_init_and_sipi - caller has to > check for relevant transition afterward > - add write barrier after setting sipi_vector > > arch/x86/kvm/lapic.c | 11 ++++++----- > arch/x86/kvm/x86.c | 15 +++++++++++++++ > include/linux/kvm_host.h | 2 ++ > 3 files changed, 23 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index 02b51dd..7986c9f 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -731,8 +731,7 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int > delivery_mode, > case APIC_DM_INIT: > if (!trig_mode || level) { > result = 1; > - vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED; > - kvm_make_request(KVM_REQ_EVENT, vcpu); > + kvm_make_request(KVM_REQ_INIT, vcpu); > kvm_vcpu_kick(vcpu); > } else { > apic_debug("Ignoring de-assert INIT to vcpu %d\n", > @@ -743,11 +742,13 @@ static int __apic_accept_irq(struct kvm_lapic *apic, > int delivery_mode, > case APIC_DM_STARTUP: > apic_debug("SIPI to vcpu %d vector 0x%02x\n", > vcpu->vcpu_id, vector); > - if (vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) { > + if (vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED || > + test_bit(KVM_REQ_INIT, &vcpu->requests)) { > result = 1; > vcpu->arch.sipi_vector = vector; > - vcpu->arch.mp_state = KVM_MP_STATE_SIPI_RECEIVED; > - kvm_make_request(KVM_REQ_EVENT, vcpu); > + /* make sure sipi_vector is visible for the receiver */ > + smp_wmb(); > + kvm_make_request(KVM_REQ_SIPI, vcpu); > kvm_vcpu_kick(vcpu); > } > break; > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index d0cf737..0be04b9 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -5641,6 +5641,15 @@ static void update_eoi_exitmap(struct kvm_vcpu *vcpu) > kvm_x86_ops->load_eoi_exitmap(vcpu, eoi_exit_bitmap); > } > > +static void kvm_check_init_and_sipi(struct kvm_vcpu *vcpu) > +{ > + if (kvm_check_request(KVM_REQ_INIT, vcpu)) > + vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED;
And here is a small race between clearing REQ_INIT and setting
INIT_RECEIVED. It can make the LAPIC drop the SIPI incorrectly. Need to
break up test and clear, doing the clear after mp_state update. Yeah...
Jan
> + if (kvm_check_request(KVM_REQ_SIPI, vcpu) &&
> + vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED)
> + vcpu->arch.mp_state = KVM_MP_STATE_SIPI_RECEIVED;
> +}
> +
> static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> {
> int r;
> @@ -5649,6 +5658,11 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> bool req_immediate_exit = 0;
>
> if (vcpu->requests) {
> + kvm_check_init_and_sipi(vcpu);
> + if (vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) {
> + r = 1;
> + goto out;
> + }
> if (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu))
> kvm_mmu_unload(vcpu);
> if (kvm_check_request(KVM_REQ_MIGRATE_TIMER, vcpu))
> @@ -6977,6 +6991,7 @@ void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
>
> int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
> {
> + kvm_check_init_and_sipi(vcpu);
> return (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&
> !vcpu->arch.apf.halted)
> || !list_empty_careful(&vcpu->async_pf.done)
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 722cae7..1a191c9 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -124,6 +124,8 @@ static inline bool is_error_page(struct page *page)
> #define KVM_REQ_MCLOCK_INPROGRESS 20
> #define KVM_REQ_EPR_EXIT 21
> #define KVM_REQ_EOIBITMAP 22
> +#define KVM_REQ_INIT 23
> +#define KVM_REQ_SIPI 24
>
> #define KVM_USERSPACE_IRQ_SOURCE_ID 0
> #define KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID 1
>
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