On Wed, Mar 13, 2013 at 12:42:34PM +0100, Jan Kiszka wrote:
> 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.
>
> This introduces APIC events for those two signals, keeping them in
> kvm_apic until kvm_apic_accept_events is run over the target vcpu
> context. kvm_apic_has_events reports to kvm_arch_vcpu_runnable if there
> are pending events, thus if vcpu blocking should end.
>
> The patch comes with the side effect of effectively obsoleting
> KVM_MP_STATE_SIPI_RECEIVED. We still accept it from user space, but
> immediately translate it to KVM_MP_STATE_INIT_RECEIVED + KVM_APIC_SIPI.
> The vcpu itself will no longer enter the KVM_MP_STATE_SIPI_RECEIVED
> state. That also means we no longer exit to user space after receiving a
> SIPI event.
>
> Furthermore, we already reset the VCPU on INIT, only fixing up the code
> segment later on when SIPI arrives. Moreover, we fix INIT handling for
> the BSP: it never enter wait-for-SIPI but directly starts over on INIT.
>
> Signed-off-by: Jan Kiszka <jan.kis...@siemens.com>
Applied, thanks.
> ---
>
> Changes in v2:
> - drop cmpxchg from INIT signaling
> - rmb on SIPI processing
> - reset sets all CPUs to 0xf000:0xfff0, RIP is fixed up on SIPI reception
>
> arch/x86/include/asm/kvm_host.h | 3 +-
> arch/x86/kvm/lapic.c | 48 +++++++++++++++++++++++++++-----
> arch/x86/kvm/lapic.h | 11 +++++++
> arch/x86/kvm/svm.c | 6 ----
> arch/x86/kvm/vmx.c | 12 +-------
> arch/x86/kvm/x86.c | 58 +++++++++++++++++++++++++-------------
> 6 files changed, 93 insertions(+), 45 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 348d859..ef7f4a5 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -345,7 +345,6 @@ struct kvm_vcpu_arch {
> unsigned long apic_attention;
> int32_t apic_arb_prio;
> int mp_state;
> - int sipi_vector;
> u64 ia32_misc_enable_msr;
> bool tpr_access_reporting;
>
> @@ -819,6 +818,7 @@ int kvm_emulate_wbinvd(struct kvm_vcpu *vcpu);
>
> void kvm_get_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int
> seg);
> int kvm_load_segment_descriptor(struct kvm_vcpu *vcpu, u16 selector, int
> seg);
> +void kvm_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, unsigned int
> vector);
>
> int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int idt_index,
> int reason, bool has_error_code, u32 error_code);
> @@ -1002,6 +1002,7 @@ int kvm_cpu_has_injectable_intr(struct kvm_vcpu *v);
> int kvm_cpu_has_interrupt(struct kvm_vcpu *vcpu);
> int kvm_arch_interrupt_allowed(struct kvm_vcpu *vcpu);
> int kvm_cpu_get_interrupt(struct kvm_vcpu *v);
> +void kvm_vcpu_reset(struct kvm_vcpu *vcpu);
>
> void kvm_define_shared_msr(unsigned index, u32 msr);
> void kvm_set_shared_msr(unsigned index, u64 val, u64 mask);
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 02b51dd..a8e9369 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -731,7 +731,11 @@ 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;
> + /* assumes that there are only KVM_APIC_INIT/SIPI */
> + apic->pending_events = (1UL << KVM_APIC_INIT);
> + /* make sure pending_events is visible before sending
> + * the request */
> + smp_wmb();
> kvm_make_request(KVM_REQ_EVENT, vcpu);
> kvm_vcpu_kick(vcpu);
> } else {
> @@ -743,13 +747,13 @@ 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) {
> - result = 1;
> - vcpu->arch.sipi_vector = vector;
> - vcpu->arch.mp_state = KVM_MP_STATE_SIPI_RECEIVED;
> - kvm_make_request(KVM_REQ_EVENT, vcpu);
> - kvm_vcpu_kick(vcpu);
> - }
> + result = 1;
> + apic->sipi_vector = vector;
> + /* make sure sipi_vector is visible for the receiver */
> + smp_wmb();
> + set_bit(KVM_APIC_SIPI, &apic->pending_events);
> + kvm_make_request(KVM_REQ_EVENT, vcpu);
> + kvm_vcpu_kick(vcpu);
> break;
>
> case APIC_DM_EXTINT:
> @@ -1860,6 +1864,34 @@ int kvm_lapic_enable_pv_eoi(struct kvm_vcpu *vcpu, u64
> data)
> addr);
> }
>
> +void kvm_apic_accept_events(struct kvm_vcpu *vcpu)
> +{
> + struct kvm_lapic *apic = vcpu->arch.apic;
> + unsigned int sipi_vector;
> +
> + if (!kvm_vcpu_has_lapic(vcpu))
> + return;
> +
> + if (test_and_clear_bit(KVM_APIC_INIT, &apic->pending_events)) {
> + kvm_lapic_reset(vcpu);
> + kvm_vcpu_reset(vcpu);
> + if (kvm_vcpu_is_bsp(apic->vcpu))
> + vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
> + else
> + vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED;
> + }
> + if (test_and_clear_bit(KVM_APIC_SIPI, &apic->pending_events) &&
> + vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) {
> + /* evaluate pending_events before reading the vector */
> + smp_rmb();
> + sipi_vector = apic->sipi_vector;
> + pr_debug("vcpu %d received sipi with vector # %x\n",
> + vcpu->vcpu_id, sipi_vector);
> + kvm_vcpu_deliver_sipi_vector(vcpu, sipi_vector);
> + vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
> + }
> +}
> +
> void kvm_lapic_init(void)
> {
> /* do not patch jump label more than once per second */
> diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
> index 1676d34..2c721b9 100644
> --- a/arch/x86/kvm/lapic.h
> +++ b/arch/x86/kvm/lapic.h
> @@ -5,6 +5,9 @@
>
> #include <linux/kvm_host.h>
>
> +#define KVM_APIC_INIT 0
> +#define KVM_APIC_SIPI 1
> +
> struct kvm_timer {
> struct hrtimer timer;
> s64 period; /* unit: ns */
> @@ -32,6 +35,8 @@ struct kvm_lapic {
> void *regs;
> gpa_t vapic_addr;
> struct page *vapic_page;
> + unsigned long pending_events;
> + unsigned int sipi_vector;
> };
> int kvm_create_lapic(struct kvm_vcpu *vcpu);
> void kvm_free_lapic(struct kvm_vcpu *vcpu);
> @@ -39,6 +44,7 @@ void kvm_free_lapic(struct kvm_vcpu *vcpu);
> int kvm_apic_has_interrupt(struct kvm_vcpu *vcpu);
> int kvm_apic_accept_pic_intr(struct kvm_vcpu *vcpu);
> int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu);
> +void kvm_apic_accept_events(struct kvm_vcpu *vcpu);
> void kvm_lapic_reset(struct kvm_vcpu *vcpu);
> u64 kvm_lapic_get_cr8(struct kvm_vcpu *vcpu);
> void kvm_lapic_set_tpr(struct kvm_vcpu *vcpu, unsigned long cr8);
> @@ -158,4 +164,9 @@ void kvm_calculate_eoi_exitmap(struct kvm_vcpu *vcpu,
> struct kvm_lapic_irq *irq,
> u64 *eoi_bitmap);
>
> +static inline bool kvm_apic_has_events(struct kvm_vcpu *vcpu)
> +{
> + return vcpu->arch.apic->pending_events;
> +}
> +
> #endif
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 907e428..7219a40 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -1199,12 +1199,6 @@ static void svm_vcpu_reset(struct kvm_vcpu *vcpu)
>
> init_vmcb(svm);
>
> - if (!kvm_vcpu_is_bsp(vcpu)) {
> - kvm_rip_write(vcpu, 0);
> - svm->vmcb->save.cs.base = svm->vcpu.arch.sipi_vector << 12;
> - svm->vmcb->save.cs.selector = svm->vcpu.arch.sipi_vector << 8;
> - }
> -
> kvm_cpuid(vcpu, &eax, &dummy, &dummy, &dummy);
> kvm_register_write(vcpu, VCPU_REGS_RDX, eax);
> }
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index f17cd2a..b73989d 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -4119,12 +4119,7 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu)
> vmx_segment_cache_clear(vmx);
>
> seg_setup(VCPU_SREG_CS);
> - if (kvm_vcpu_is_bsp(&vmx->vcpu))
> - vmcs_write16(GUEST_CS_SELECTOR, 0xf000);
> - else {
> - vmcs_write16(GUEST_CS_SELECTOR, vmx->vcpu.arch.sipi_vector <<
> 8);
> - vmcs_writel(GUEST_CS_BASE, vmx->vcpu.arch.sipi_vector << 12);
> - }
> + vmcs_write16(GUEST_CS_SELECTOR, 0xf000);
>
> seg_setup(VCPU_SREG_DS);
> seg_setup(VCPU_SREG_ES);
> @@ -4147,10 +4142,7 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu)
> vmcs_writel(GUEST_SYSENTER_EIP, 0);
>
> vmcs_writel(GUEST_RFLAGS, 0x02);
> - if (kvm_vcpu_is_bsp(&vmx->vcpu))
> - kvm_rip_write(vcpu, 0xfff0);
> - else
> - kvm_rip_write(vcpu, 0);
> + kvm_rip_write(vcpu, 0xfff0);
>
> vmcs_writel(GUEST_GDTR_BASE, 0);
> vmcs_write32(GUEST_GDTR_LIMIT, 0xffff);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index b891ac3..a7e51ae 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -162,8 +162,6 @@ u64 __read_mostly host_xcr0;
>
> static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt);
>
> -static void kvm_vcpu_reset(struct kvm_vcpu *vcpu);
> -
> static inline void kvm_async_pf_hash_reset(struct kvm_vcpu *vcpu)
> {
> int i;
> @@ -2823,10 +2821,9 @@ static void kvm_vcpu_ioctl_x86_get_vcpu_events(struct
> kvm_vcpu *vcpu,
> events->nmi.masked = kvm_x86_ops->get_nmi_mask(vcpu);
> events->nmi.pad = 0;
>
> - events->sipi_vector = vcpu->arch.sipi_vector;
> + events->sipi_vector = 0; /* never valid when reporting to user space */
>
> events->flags = (KVM_VCPUEVENT_VALID_NMI_PENDING
> - | KVM_VCPUEVENT_VALID_SIPI_VECTOR
> | KVM_VCPUEVENT_VALID_SHADOW);
> memset(&events->reserved, 0, sizeof(events->reserved));
> }
> @@ -2857,8 +2854,9 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct
> kvm_vcpu *vcpu,
> vcpu->arch.nmi_pending = events->nmi.pending;
> kvm_x86_ops->set_nmi_mask(vcpu, events->nmi.masked);
>
> - if (events->flags & KVM_VCPUEVENT_VALID_SIPI_VECTOR)
> - vcpu->arch.sipi_vector = events->sipi_vector;
> + if (events->flags & KVM_VCPUEVENT_VALID_SIPI_VECTOR &&
> + kvm_vcpu_has_lapic(vcpu))
> + vcpu->arch.apic->sipi_vector = events->sipi_vector;
>
> kvm_make_request(KVM_REQ_EVENT, vcpu);
>
> @@ -5713,6 +5711,12 @@ static int vcpu_enter_guest(struct kvm_vcpu *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) {
> + r = 1;
> + goto out;
> + }
> +
> inject_pending_event(vcpu);
>
> /* enable NMI/IRQ window open exits if needed */
> @@ -5847,14 +5851,6 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
> int r;
> struct kvm *kvm = vcpu->kvm;
>
> - if (unlikely(vcpu->arch.mp_state == KVM_MP_STATE_SIPI_RECEIVED)) {
> - pr_debug("vcpu %d received sipi with vector # %x\n",
> - vcpu->vcpu_id, vcpu->arch.sipi_vector);
> - kvm_lapic_reset(vcpu);
> - kvm_vcpu_reset(vcpu);
> - vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
> - }
> -
> vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
> r = vapic_enter(vcpu);
> if (r) {
> @@ -5871,8 +5867,8 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
> srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
> kvm_vcpu_block(vcpu);
> vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
> - if (kvm_check_request(KVM_REQ_UNHALT, vcpu))
> - {
> + if (kvm_check_request(KVM_REQ_UNHALT, vcpu)) {
> + kvm_apic_accept_events(vcpu);
> switch(vcpu->arch.mp_state) {
> case KVM_MP_STATE_HALTED:
> vcpu->arch.mp_state =
> @@ -5880,7 +5876,8 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
> case KVM_MP_STATE_RUNNABLE:
> vcpu->arch.apf.halted = false;
> break;
> - case KVM_MP_STATE_SIPI_RECEIVED:
> + case KVM_MP_STATE_INIT_RECEIVED:
> + break;
> default:
> r = -EINTR;
> break;
> @@ -6015,6 +6012,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu,
> struct kvm_run *kvm_run)
>
> if (unlikely(vcpu->arch.mp_state == KVM_MP_STATE_UNINITIALIZED)) {
> kvm_vcpu_block(vcpu);
> + kvm_apic_accept_events(vcpu);
> clear_bit(KVM_REQ_UNHALT, &vcpu->requests);
> r = -EAGAIN;
> goto out;
> @@ -6171,6 +6169,7 @@ int kvm_arch_vcpu_ioctl_get_sregs(struct kvm_vcpu *vcpu,
> int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
> struct kvm_mp_state *mp_state)
> {
> + kvm_apic_accept_events(vcpu);
> mp_state->mp_state = vcpu->arch.mp_state;
> return 0;
> }
> @@ -6178,7 +6177,15 @@ int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu
> *vcpu,
> int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
> struct kvm_mp_state *mp_state)
> {
> - vcpu->arch.mp_state = mp_state->mp_state;
> + if (!kvm_vcpu_has_lapic(vcpu) &&
> + mp_state->mp_state != KVM_MP_STATE_RUNNABLE)
> + return -EINVAL;
> +
> + if (mp_state->mp_state == KVM_MP_STATE_SIPI_RECEIVED) {
> + vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED;
> + set_bit(KVM_APIC_SIPI, &vcpu->arch.apic->pending_events);
> + } else
> + vcpu->arch.mp_state = mp_state->mp_state;
> kvm_make_request(KVM_REQ_EVENT, vcpu);
> return 0;
> }
> @@ -6515,7 +6522,7 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
> kvm_x86_ops->vcpu_free(vcpu);
> }
>
> -static void kvm_vcpu_reset(struct kvm_vcpu *vcpu)
> +void kvm_vcpu_reset(struct kvm_vcpu *vcpu)
> {
> atomic_set(&vcpu->arch.nmi_queued, 0);
> vcpu->arch.nmi_pending = 0;
> @@ -6545,6 +6552,17 @@ static void kvm_vcpu_reset(struct kvm_vcpu *vcpu)
> kvm_x86_ops->vcpu_reset(vcpu);
> }
>
> +void kvm_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, unsigned int vector)
> +{
> + struct kvm_segment cs;
> +
> + kvm_get_segment(vcpu, &cs, VCPU_SREG_CS);
> + cs.selector = vector << 8;
> + cs.base = vector << 12;
> + kvm_set_segment(vcpu, &cs, VCPU_SREG_CS);
> + kvm_rip_write(vcpu, 0);
> +}
> +
> int kvm_arch_hardware_enable(void *garbage)
> {
> struct kvm *kvm;
> @@ -6988,7 +7006,7 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
> return (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&
> !vcpu->arch.apf.halted)
> || !list_empty_careful(&vcpu->async_pf.done)
> - || vcpu->arch.mp_state == KVM_MP_STATE_SIPI_RECEIVED
> + || kvm_apic_has_events(vcpu)
> || atomic_read(&vcpu->arch.nmi_queued) ||
> (kvm_arch_interrupt_allowed(vcpu) &&
> kvm_cpu_has_interrupt(vcpu));
> --
> 1.7.3.4
--
Gleb.
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