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Re: [PATCH] x86/APIC: Remove x2APIC pure cluster mode
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Matthew Barnes <matthew.barnes@xxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 24 Sep 2024 17:27:39 +0200
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- Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx, Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>, Community Manager <community.manager@xxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>
- Delivery-date: Tue, 24 Sep 2024 15:27:47 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 24.09.2024 17:10, Roger Pau Monné wrote:
> On Mon, Sep 23, 2024 at 03:35:59PM +0100, Matthew Barnes wrote:
>> With the introduction of mixed x2APIC mode (using cluster addressing for
>> IPIs and physical for external interrupts) the use of pure cluster mode
>> doesn't have any benefit.
>>
>> Remove the mode itself, leaving only the code required for logical
>> addressing when sending IPIs.
>>
>> Implements: https://gitlab.com/xen-project/xen/-/issues/189
>
> There's at least one extra bit which I would also like to see removed,
> either in this patch, or as following patch.
>
> In struct arch_irq_desc we have 3 cpumasks: cpu_mask, old_cpu_mask and
> pending_mask. After dropping cluster mode for external interrupts,
> those fields could become integers AFACT, as now interrupts can only
> target a single CPU opposed to a logical CPU set.
Yeah, that very much wants to be a separate change.
Jan
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