Re: [Xen-devel] [PATCH v2] x86/passthrough: fix migration of MSI when using posted interrupts

[Jan Beulich <jbeulich@xxxxxxxx>]

On 30.10.2019 19:01, Joe Jin wrote:
> On 10/30/19 10:23 AM, Roger Pau Monné wrote:
>> On Wed, Oct 30, 2019 at 09:38:16AM -0700, Joe Jin wrote:
>>> On 10/30/19 1:24 AM, Roger Pau Monné wrote:
>>>> Can you try to add the following debug patch on top of the existing
>>>> one and report the output that you get on the Xen console?
>>>
>>> Applied debug patch and run the test again, not of any log printed,
>>> attached Xen log on serial console, seems pi_update_irte() not been
>>> called for iommu_intpost was false.
>>
>> I have to admit I'm lost at this point. Does it mean the original
>> issue had nothing to do with posted interrupts?
> 
> Looks when inject irq by vlapic_set_irq(), it checked by
> hvm_funcs.deliver_posted_intr rather than iommu_intpost:
> 
>  176     if ( hvm_funcs.deliver_posted_intr )
>  177         hvm_funcs.deliver_posted_intr(target, vec);
> 
> And deliver_posted_intr() would be there, when vmx enabled:
> 
> (XEN) HVM: VMX enabled
> (XEN) HVM: Hardware Assisted Paging (HAP) detected
> (XEN) HVM: HAP page sizes: 4kB, 2MB, 1GB

I can't see the connection. start_vmx() has

    if ( cpu_has_vmx_posted_intr_processing )
    {
        alloc_direct_apic_vector(&posted_intr_vector, 
pi_notification_interrupt);
        if ( iommu_intpost )
            alloc_direct_apic_vector(&pi_wakeup_vector, pi_wakeup_interrupt);

        vmx_function_table.deliver_posted_intr = vmx_deliver_posted_intr;
        vmx_function_table.sync_pir_to_irr     = vmx_sync_pir_to_irr;
        vmx_function_table.test_pir            = vmx_test_pir;
    }

i.e. the hook is present only when posted interrupts are
available in general. I.e. also with just CPU-side posted
interrupts, yes, which gets confirmed by your "apicv=0"
test. Yet with just CPU-side posted interrupts I'm
struggling again to understand your original problem
description, and the need to fiddle with IOMMU side code.

Jan

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel