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    SubjectRe: [PATCH v4] x86/xen: Add support for HVMOP_set_evtchn_upcall_vector
    From
    On 03.11.2022 16:41, Jan Beulich wrote:
    > On 03.11.2022 14:38, Jan Beulich wrote:
    >> On 29.07.2022 09:04, Jane Malalane wrote:
    >>> @@ -125,6 +130,9 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_xen_hvm_callback)
    >>> {
    >>> struct pt_regs *old_regs = set_irq_regs(regs);
    >>>
    >>> + if (xen_percpu_upcall)
    >>> + ack_APIC_irq();
    >>> +
    >>> inc_irq_stat(irq_hv_callback_count);
    >>>
    >>> xen_hvm_evtchn_do_upcall();
    >>> @@ -168,6 +176,15 @@ static int xen_cpu_up_prepare_hvm(unsigned int cpu)
    >>> if (!xen_have_vector_callback)
    >>> return 0;
    >>>
    >>> + if (xen_percpu_upcall) {
    >>> + rc = xen_set_upcall_vector(cpu);
    >>
    >> From all I can tell at least for APs this happens before setup_local_apic().
    >> With there being APIC interaction in this operation mode, as seen e.g. in
    >> the earlier hunk above, I think this is logically wrong. And it leads to
    >> apic_pending_intr_clear() issuing its warning: The vector registration, as
    >> an intentional side effect, marks the vector as pending. Unless IRQs were
    >> enabled at any point between the registration and the check, there's
    >> simply no way for the corresponding IRR bit to be dealt with (by
    >> propagating to ISR when the interrupt is delivered, and then being cleared
    >> from ISR by EOI).
    >
    > With Roger's help I now have a pointer to osstest also exposing the issue:
    >
    > http://logs.test-lab.xenproject.org/osstest/logs/174592/test-amd64-amd64-xl-pvhv2-intel/huxelrebe0---var-log-xen-console-guest-debian.guest.osstest.log.gz

    I've noticed only now that my mail to Jane bounced, and I'm now told
    she's no longer in her role at Citrix. Since I don't expect to have time
    to investigate an appropriate solution here, may I ask whether one of
    the two of you could look into this, being the maintainers of this code?

    Thanks, Jan

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