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RE: [PATCH v4 4/4] x86/iommu: pass full IO-APIC RTE for remapping table update
- To: Pau Monné, Roger <roger.pau@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
- Date: Tue, 1 Aug 2023 02:58:32 +0000
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- Cc: Pau Monné, Roger <roger.pau@xxxxxxxxxx>, "Beulich, Jan" <JBeulich@xxxxxxxx>, "andrew.cooper3@xxxxxxxxxx" <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Paul Durrant <paul@xxxxxxx>
- Delivery-date: Tue, 01 Aug 2023 02:59:01 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Thread-index: AQHZwToNmh8G0I7e7EOZhmA6b/SBHq/UxZCw
- Thread-topic: [PATCH v4 4/4] x86/iommu: pass full IO-APIC RTE for remapping table update
> From: Roger Pau Monne <roger.pau@xxxxxxxxxx>
> Sent: Friday, July 28, 2023 5:57 PM
>
> So that the remapping entry can be updated atomically when possible.
>
> Doing such update atomically will avoid Xen having to mask the IO-APIC
> pin prior to performing any interrupt movements (ie: changing the
> destination and vector fields), as the interrupt remapping entry is
> always consistent.
>
> This also simplifies some of the logic on both VT-d and AMD-Vi
> implementations, as having the full RTE available instead of half of
> it avoids to possibly read and update the missing other half from
> hardware.
>
> While there remove the explicit zeroing of new_ire fields in
> ioapic_rte_to_remap_entry() and initialize the variable at definition
> so all fields are zeroed. Note fields could be also initialized with
> final values at definition, but I found that likely too much to be
> done at this time.
>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
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