On 2013-03-13 11:31, Gleb Natapov wrote:
> On Wed, Mar 13, 2013 at 09:50:55AM +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.kiszka@xxxxxxxxxxx>
>> ---
>> arch/x86/include/asm/kvm_host.h | 3 +-
>> arch/x86/kvm/lapic.c | 47 ++++++++++++++++++++++++++-----
>> arch/x86/kvm/lapic.h | 11 +++++++
>> arch/x86/kvm/svm.c | 5 +---
>> arch/x86/kvm/vmx.c | 4 ---
>> arch/x86/kvm/x86.c | 57 +++++++++++++++++++++++++-------------
>> 6 files changed, 90 insertions(+), 37 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..6c16230 100644
>> --- a/arch/x86/kvm/lapic.c
>> +++ b/arch/x86/kvm/lapic.c
>> @@ -685,6 +685,7 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
>> {
>> int result = 0;
>> struct kvm_vcpu *vcpu = apic->vcpu;
>> + unsigned long e;
>>
>> switch (delivery_mode) {
>> case APIC_DM_LOWEST:
>> @@ -731,7 +732,11 @@ 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;
>> + e = apic->pending_events;
>> + while (!test_bit(KVM_APIC_INIT, &e))
>> + e = cmpxchg(&apic->pending_events, e,
>> + (e | (1UL << KVM_APIC_INIT)) &
>> + ~(1UL << KVM_APIC_SIPI));
> Can you please add a comment why is this needed.
Even better, I'll remove it (see the other thread).
>
>> kvm_make_request(KVM_REQ_EVENT, vcpu);
>> kvm_vcpu_kick(vcpu);
>> } else {
>> @@ -743,13 +748,13 @@ 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 +1865,32 @@ 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) {
>> + 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..796601a 100644
>> --- a/arch/x86/kvm/svm.c
>> +++ b/arch/x86/kvm/svm.c
>> @@ -1199,11 +1199,8 @@ static void svm_vcpu_reset(struct kvm_vcpu *vcpu)
>>
>> init_vmcb(svm);
>>
>> - if (!kvm_vcpu_is_bsp(vcpu)) {
>> + if (!kvm_vcpu_is_bsp(vcpu))
>> kvm_rip_write(vcpu, 0);
> Table 9-1 in SDM says that after INIT reset RIP is 0xfff0. Not
> mentioning AP or BSP. We should drop any mentioning of kvm_vcpu_is_bsp()
> in vmx and svm reset code and thing should just work.
SDM says that APs start up at 0x000VV000 (with VV == SIPI vector) - this
implies RIP is 0. I suppose no SMP guest would boot if we change this.
>
>> - 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..5b862ed 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -4121,10 +4121,6 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu)
>> 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);
>> - }
>>
>> seg_setup(VCPU_SREG_DS);
>> seg_setup(VCPU_SREG_ES);
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index b891ac3..37c0807 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;
> This looks out of place in this patch. Why is it needed?
It is required as long as we support MP_STATE_SIPI_RECEIVED as input
from user space.
>
>>
>> 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);
> I think we can drop this. If INIT happens while vcpu is halted it will
> become runnable here and kvm_apic_accept_events() will be called in
> vcpu_enter_guest().
I'm not that sure, but I will recheck carefully.
Jan
--
Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
Corporate Competence Center Embedded Linux
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