Re: [PATCH 2/3] PCI: hv: unmap MSI interrupt on the nested root partition teardown path

[sashiko-bot@kernel.org]

> From: Wei Liu <wei.liu@kernel.org>
> 
> On a nested root partition the vPCI MSI/MSI-X interrupts of vmbus
> devices (e.g. the MANA NIC) are mapped in the hypervisor with a
> MAP_DEVICE_INTERRUPT hypercall.  This is done from hv_arch_irq_unmask()
> -> hv_map_msi_interrupt() because the nested hypervisor performs the
> interrupt remapping and a RETARGET_INTERRUPT is not usable there.
> 
> The mapping was never removed: hv_arch_irq_unmask() called
> hv_map_msi_interrupt(data, NULL), so the returned hv_interrupt_entry was
> discarded, and hv_msi_free() tears the interrupt down with a vmbus
> PCI_DELETE_INTERRUPT message (hv_int_desc_free()) without issuing
> UNMAP_DEVICE_INTERRUPT.
> 
> This has led to MSHV rejecting already-mapped (vp, vector) pair from
> being used. When this happens during early boot, the system hangs.
> 
> Keep the hypervisor mapping in sync with the kernel's interrupt
> lifecycle.
> 
> The mapping is only created on x86 (hv_arch_irq_unmask() is a stub on
> arm64), so the unmap hypercall is guarded accordingly.
> 
> Signed-off-by: Wei Liu <wei.liu@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

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