Re: [PATCH v6] KVM: x86: Add x2APIC "features" to control EOI broadcast suppression

[David Woodhouse]

On Wed, 2026-01-28 at 05:17 +0000, Khushit Shah wrote:
> 
> How about we make an explicit _ENABLE_ bit for split IRQCHIP?
> When/if in-kernel IRQCHIP starts supporting I/O APIC 0x20, we
> can add a separate bit for that in the CAP. 
> 
> This way:
> - The flag name (KVM_X2APIC_SPLIT_ENABLE_SEOIB) is self-documenting.
> - We always advertise it in KVM_CHECK_EXTENSION.
> - Enabling requires split IRQCHIP to be configured first.
> - Mutex protects against races with KVM_CAP_SPLIT_IRQCHIP.

Ick. The more we iterate on this, the more convinced I am that we
should just enable it for I/O APIC at the same time. Userspace has to
explicitly opt in to the combination of kernel I/O APIC and SEOIB
anyway.

So I'll just bow out of the conversation; do whatever you think best.

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