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Re: [PATCH] x86/HVM: don't mark evtchn upcall vector as pending when vLAPIC is disabled
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 21 Nov 2022 13:06:38 +0100
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Paul Durrant <paul@xxxxxxx>
- Delivery-date: Mon, 21 Nov 2022 12:06:48 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 21.11.2022 09:33, Jan Beulich wrote:
> On 18.11.2022 15:26, Roger Pau Monné wrote:
>> Maybe best to add an ASSERT in vlapic_set_irq() to be sure the lapic is
>> enabled, as other callers already check this before trying to inject?
>
> Perhaps, yes (once we've fixed paths where the check is presently
> missing).
Actually - no, such an ASSERT() would then be racy against the vLAPIC
being disabled elsewhere at this very moment. It would at best be valid
when done on the vCPU in question. The SDM also provides for this: "The
reception of any interrupt or transmission of any IPIs that are in
progress when the local APIC is disabled are completed before the local
APIC enters the software-disabled state." We don't follow this to the
letter, but you get the point.
Jan
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