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    SubjectRe: [PATCH v4 14/21] KVM: arm64: Support SDEI_EVENT_{COMPLETE, COMPLETE_AND_RESUME} hypercall
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    Hi Eric,

    On 11/10/21 6:58 PM, Eric Auger wrote:
    > On 8/15/21 2:13 AM, Gavin Shan wrote:
    >> This supports SDEI_EVENT_{COMPLETE, COMPLETE_AND_RESUME} hypercall.
    >> They are used by the guest to notify the completion of the SDEI
    >> event in the handler. The registers are changed according to the
    >> SDEI specification as below:
    >>
    >> * x0 - x17, PC and PState are restored to what values we had in
    >> the interrupted context.
    >>
    >> * If it's SDEI_EVENT_COMPLETE_AND_RESUME hypercall, IRQ exception
    >> is injected.
    >>
    >> Signed-off-by: Gavin Shan <gshan@redhat.com>
    >> ---
    >> arch/arm64/include/asm/kvm_emulate.h | 1 +
    >> arch/arm64/include/asm/kvm_host.h | 1 +
    >> arch/arm64/kvm/hyp/exception.c | 7 +++
    >> arch/arm64/kvm/inject_fault.c | 27 ++++++++++
    >> arch/arm64/kvm/sdei.c | 75 ++++++++++++++++++++++++++++
    >> 5 files changed, 111 insertions(+)
    >>
    >> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
    >> index fd418955e31e..923b4d08ea9a 100644
    >> --- a/arch/arm64/include/asm/kvm_emulate.h
    >> +++ b/arch/arm64/include/asm/kvm_emulate.h
    >> @@ -37,6 +37,7 @@ bool kvm_condition_valid32(const struct kvm_vcpu *vcpu);
    >> void kvm_skip_instr32(struct kvm_vcpu *vcpu);
    >>
    >> void kvm_inject_undefined(struct kvm_vcpu *vcpu);
    >> +void kvm_inject_irq(struct kvm_vcpu *vcpu);
    >> void kvm_inject_vabt(struct kvm_vcpu *vcpu);
    >> void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr);
    >> void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr);
    >> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
    >> index 46f363aa6524..1824f7e1f9ab 100644
    >> --- a/arch/arm64/include/asm/kvm_host.h
    >> +++ b/arch/arm64/include/asm/kvm_host.h
    >> @@ -437,6 +437,7 @@ struct kvm_vcpu_arch {
    >> #define KVM_ARM64_EXCEPT_AA32_UND (0 << 9)
    >> #define KVM_ARM64_EXCEPT_AA32_IABT (1 << 9)
    >> #define KVM_ARM64_EXCEPT_AA32_DABT (2 << 9)
    >> +#define KVM_ARM64_EXCEPT_AA32_IRQ (3 << 9)
    >> /* For AArch64: */
    >> #define KVM_ARM64_EXCEPT_AA64_ELx_SYNC (0 << 9)
    >> #define KVM_ARM64_EXCEPT_AA64_ELx_IRQ (1 << 9)
    >> diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c
    >> index 0418399e0a20..ef458207d152 100644
    >> --- a/arch/arm64/kvm/hyp/exception.c
    >> +++ b/arch/arm64/kvm/hyp/exception.c
    >> @@ -310,6 +310,9 @@ static void kvm_inject_exception(struct kvm_vcpu *vcpu)
    >> case KVM_ARM64_EXCEPT_AA32_DABT:
    >> enter_exception32(vcpu, PSR_AA32_MODE_ABT, 16);
    >> break;
    >> + case KVM_ARM64_EXCEPT_AA32_IRQ:
    >> + enter_exception32(vcpu, PSR_AA32_MODE_IRQ, 4);
    >> + break;
    >> default:
    >> /* Err... */
    >> break;
    >> @@ -320,6 +323,10 @@ static void kvm_inject_exception(struct kvm_vcpu *vcpu)
    >> KVM_ARM64_EXCEPT_AA64_EL1):
    >> enter_exception64(vcpu, PSR_MODE_EL1h, except_type_sync);
    >> break;
    >> + case (KVM_ARM64_EXCEPT_AA64_ELx_IRQ |
    >> + KVM_ARM64_EXCEPT_AA64_EL1):
    >> + enter_exception64(vcpu, PSR_MODE_EL1h, except_type_irq);
    >> + break;
    >> default:
    >> /*
    >> * Only EL1_SYNC makes sense so far, EL2_{SYNC,IRQ}
    >> diff --git a/arch/arm64/kvm/inject_fault.c b/arch/arm64/kvm/inject_fault.c
    >> index b47df73e98d7..3a8c55867d2f 100644
    >> --- a/arch/arm64/kvm/inject_fault.c
    >> +++ b/arch/arm64/kvm/inject_fault.c
    >> @@ -66,6 +66,13 @@ static void inject_undef64(struct kvm_vcpu *vcpu)
    >> vcpu_write_sys_reg(vcpu, esr, ESR_EL1);
    >> }
    >>
    >> +static void inject_irq64(struct kvm_vcpu *vcpu)
    >> +{
    >> + vcpu->arch.flags |= (KVM_ARM64_EXCEPT_AA64_EL1 |
    >> + KVM_ARM64_EXCEPT_AA64_ELx_IRQ |
    >> + KVM_ARM64_PENDING_EXCEPTION);
    >> +}
    >> +
    >> #define DFSR_FSC_EXTABT_LPAE 0x10
    >> #define DFSR_FSC_EXTABT_nLPAE 0x08
    >> #define DFSR_LPAE BIT(9)
    >> @@ -77,6 +84,12 @@ static void inject_undef32(struct kvm_vcpu *vcpu)
    >> KVM_ARM64_PENDING_EXCEPTION);
    >> }
    >>
    >> +static void inject_irq32(struct kvm_vcpu *vcpu)
    >> +{
    >> + vcpu->arch.flags |= (KVM_ARM64_EXCEPT_AA32_IRQ |
    >> + KVM_ARM64_PENDING_EXCEPTION);
    >> +}
    >> +
    >> /*
    >> * Modelled after TakeDataAbortException() and TakePrefetchAbortException
    >> * pseudocode.
    >> @@ -160,6 +173,20 @@ void kvm_inject_undefined(struct kvm_vcpu *vcpu)
    >> inject_undef64(vcpu);
    >> }
    >>
    >> +/**
    >> + * kvm_inject_irq - inject an IRQ into the guest
    >> + *
    >> + * It is assumed that this code is called from the VCPU thread and that the
    >> + * VCPU therefore is not currently executing guest code.
    >> + */
    >> +void kvm_inject_irq(struct kvm_vcpu *vcpu)
    >> +{
    >> + if (vcpu_el1_is_32bit(vcpu))
    >> + inject_irq32(vcpu);
    >> + else
    >> + inject_irq64(vcpu);
    >> +}
    >> +
    >> void kvm_set_sei_esr(struct kvm_vcpu *vcpu, u64 esr)
    >> {
    >> vcpu_set_vsesr(vcpu, esr & ESR_ELx_ISS_MASK);
    >> diff --git a/arch/arm64/kvm/sdei.c b/arch/arm64/kvm/sdei.c
    >> index b5d6d1ed3858..1e8e213c9d70 100644
    >> --- a/arch/arm64/kvm/sdei.c
    >> +++ b/arch/arm64/kvm/sdei.c
    >> @@ -308,6 +308,75 @@ static unsigned long kvm_sdei_hypercall_context(struct kvm_vcpu *vcpu)
    >> return ret;
    >> }
    >>
    >> +static unsigned long kvm_sdei_hypercall_complete(struct kvm_vcpu *vcpu,
    >> + bool resume)
    >> +{
    >> + struct kvm *kvm = vcpu->kvm;
    >> + struct kvm_sdei_kvm *ksdei = kvm->arch.sdei;
    >> + struct kvm_sdei_vcpu *vsdei = vcpu->arch.sdei;
    >> + struct kvm_sdei_kvm_event *kske = NULL;
    >> + struct kvm_sdei_vcpu_event *ksve = NULL;
    >> + struct kvm_sdei_vcpu_regs *regs;
    >> + unsigned long ret = SDEI_SUCCESS;
    > for the RESUME you never seem to read resume_addr arg? How does it work?
    > I don't get the irq injection path. Please could you explain?

    The guest kernel uses COMPLETE and COMPLETE_AND_RESUME hypercalls to notify the
    SDEI event has been acknoledged by it. The difference between them is COMPLETE_AND_RESUME
    fires the pending interrupts, but COMPLETE doesn't.

    >> + int index;
    >> +
    >> + /* Sanity check */
    >> + if (!(ksdei && vsdei)) {
    >> + ret = SDEI_NOT_SUPPORTED;
    >> + goto out;
    >> + }
    >> +
    >> + spin_lock(&vsdei->lock);
    >> + if (vsdei->critical_event) {
    >> + ksve = vsdei->critical_event;
    >> + regs = &vsdei->state.critical_regs;
    >> + vsdei->critical_event = NULL;
    >> + vsdei->state.critical_num = KVM_SDEI_INVALID_NUM;
    >> + } else if (vsdei->normal_event) {
    >> + ksve = vsdei->normal_event;
    >> + regs = &vsdei->state.normal_regs;
    >> + vsdei->normal_event = NULL;
    >> + vsdei->state.normal_num = KVM_SDEI_INVALID_NUM;
    >> + } else {
    >> + ret = SDEI_DENIED;
    >> + goto unlock;
    >> + }
    >> +
    >> + /* Restore registers: x0 -> x17, PC, PState */
    >> + for (index = 0; index < ARRAY_SIZE(regs->regs); index++)
    >> + vcpu_set_reg(vcpu, index, regs->regs[index]);
    >> +
    >> + *vcpu_cpsr(vcpu) = regs->pstate;
    >> + *vcpu_pc(vcpu) = regs->pc;
    >> +
    >> + /* Inject interrupt if needed */
    >> + if (resume)
    >> + kvm_inject_irq(vcpu);
    >> +
    >> + /*
    >> + * Update state. We needn't take lock in order to update the KVM
    >> + * event state as it's not destroyed because of the reference
    >> + * count.
    >> + */
    >> + kske = ksve->kske;
    >> + ksve->state.refcount--;
    >> + kske->state.refcount--;
    > why double --?

    On each SDEI event is queued for delivery, both reference count are increased. I guess
    it's a bit confusing. I will change in next revision:

    ksve->state.refcount: Increased on each SDEI event is queued for delivered
    kske->state.refcount: Increased on each @ksve is created


    >> + if (!ksve->state.refcount) {
    > why not using a struct kref directly?

    The reason is kref isn't friendly to userspace. This field (@refcount) needs to be
    migrated :)

    >> + list_del(&ksve->link);
    >> + kfree(ksve);
    >> + }
    >> +
    >> + /* Make another request if there is pending event */
    >> + if (!(list_empty(&vsdei->critical_events) &&
    >> + list_empty(&vsdei->normal_events)))
    >> + kvm_make_request(KVM_REQ_SDEI, vcpu);
    >> +
    >> +unlock:
    >> + spin_unlock(&vsdei->lock);
    >> +out:
    >> + return ret;
    >> +}
    >> +
    >> static unsigned long kvm_sdei_hypercall_unregister(struct kvm_vcpu *vcpu)
    >> {
    >> struct kvm *kvm = vcpu->kvm;
    >> @@ -628,7 +697,13 @@ int kvm_sdei_hypercall(struct kvm_vcpu *vcpu)
    >> ret = kvm_sdei_hypercall_context(vcpu);
    >> break;
    >> case SDEI_1_0_FN_SDEI_EVENT_COMPLETE:
    >> + has_result = false;
    >> + ret = kvm_sdei_hypercall_complete(vcpu, false);
    >> + break;
    >> case SDEI_1_0_FN_SDEI_EVENT_COMPLETE_AND_RESUME:
    >> + has_result = false;
    >> + ret = kvm_sdei_hypercall_complete(vcpu, true);
    >> + break;
    >> case SDEI_1_0_FN_SDEI_EVENT_UNREGISTER:
    >> ret = kvm_sdei_hypercall_unregister(vcpu);
    >> break;
    >>

    Thanks,
    Gavin

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