On Fri, 2024-08-02 at 07:55 -0700, Sean Christopherson wrote:

On Fri, Aug 02, 2024, David Woodhouse wrote:

quoted

On Thu, 2024-08-01 at 20:54 +0200, Thomas Gleixner wrote:

quoted

On Thu, Aug 01 2024 at 16:14, Michael Kelley wrote:

quoted

I don't have a convenient way to test my sequence on KVM.

But still fails in KVM

By KVM you mean the in-kernel one that we want to kill because everyone
should be using userspace IRQ chips these days?

What exactly do you want to kill?  In-kernel local APIC obviously needs to stay
for APICv/AVIC.

The legacy PIT, PIC and I/O APIC.

And IMO, encouraging userspace I/O APIC emulation is a net negative for KVM and
the community as a whole, as the number of VMMs in use these days results in a
decent amount of duplicated work in userspace VMMs, especially when accounting
for hardware and software quirks.

I don't particularly care, but I thought the general trend was towards
split irqchip mode, with the local APIC in-kernel but i8259 PIC and I/O
APIC (and the i8254 PIT, which was the topic of this discussion) being
done in userspace.

Especially if you want to support guests with APIC IDs > 255 :)