Re: [Xen-devel] [PATCH for-4.13 v2 2/2] x86/ioapic: fix clear_IO_APIC_pin write of raw entries

[Jan Beulich <jbeulich@xxxxxxxx>]

On 10.11.2019 10:25, Roger Pau Monne wrote:
> clear_IO_APIC_pin can be called after the iommu has been enabled, and
> using raw reads and writes to modify IO-APIC entries that have been
> setup to use interrupt remapping can lead to issues as some of the
> fields have different meaning when the IO-APIC entry is setup to point
> to an interrupt remapping table entry.
> 
> The following ASSERT in AMD IOMMU code triggers afterwards as a result
> of the raw changes to IO-APIC entries performed by clear_IO_APIC_pin.
> 
> (XEN) [   10.082154] ENABLING IO-APIC IRQs
> (XEN) [   10.087789]  -> Using new ACK method
> (XEN) [   10.093738] Assertion 'get_rte_index(rte) == offset' failed at 
> iommu_intr.c:328
> 
> Fix this by making sure that modifications to entries are performed in
> non raw mode.

... when fields are affected which may either have changed meaning
with interrupt remapping, or which may need mirroring into IRTEs.

> Reported-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

With the above addition (or something substantially similar)
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Of course the adjustment is easy enough to do while committing.

Jan

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