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Re: [PATCH v4] x86/xen: Add support for HVMOP_set_evtchn_upcall_vector
- To: Jane Malalane <jane.malalane@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 3 Nov 2022 16:41:19 +0100
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- Cc: Juergen Gross <jgross@xxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, x86@xxxxxxxxxx, "H. Peter Anvin" <hpa@xxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>, Maximilian Heyne <mheyne@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, LKML <linux-kernel@xxxxxxxxxxxxxxx>
- Delivery-date: Thu, 03 Nov 2022 15:41:33 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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
Jan
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