Re: [Xen-devel] [PATCH v12 3/7] VT-d: Introduce new fields in msi_desc to track binding with guest interrupt

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Gao, Chao
> Sent: Thursday, April 6, 2017 8:30 AM
> 
> msi_msg_to_remap_entry() is buggy when the live IRTE is in posted format. It
> wrongly inherits the 'im' field meaning the IRTE is in posted format but
> updates all the other fields to remapping format.
> 
> There are also two situations that lead to the above issue. One is some
> callers
> really want to change the IRTE to remapped format. The other is some callers
> only want to update msi message (e.g. set msi affinity) for they don't aware
> that this msi is binded with a guest interrupt. We should suppress update
> in the second situation. To distinguish them, straightforwardly, we can let
> caller specify which format of IRTE they want update to. It isn't feasible for
> making all callers be aware of the binding with guest interrupt will cause a
> far more complicated change (including the interfaces exposed to IOAPIC and
> MSI). Also some callings happen in interrupt context where we can't acquire
> d->event_lock to read struct hvm_pirq_dpci.
> 
> This patch introduces two new fields in msi_desc to track binding with a
> guest
> interrupt such that msi_msg_to_remap_entry() can get the binding and
> update
> IRTE accordingly. After that change, pi_update_irte() can utilize
> msi_msg_to_remap_entry() to update IRTE to posted format.
> 
> Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
> Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>

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