Re: [PATCH 0/4] KVM: arm64: vgic: Locking fixes

[Oliver Upton <oliver.upton@linux.dev>]

On Thu, May 18, 2023 at 11:09:14AM +0100, Jean-Philippe Brucker wrote:
> Another fun locking puzzle, between the new config_lock and srcu.
> Patch 1 attempts to fix it, and the other patches fix simpler issues.
> 
> I got these lockdep reports while running KVM QEMU on a TCG QEMU, but it
> can also be triggered by running the vgic_irq kselftest on TCG QEMU.
> Now, with the fix and lockdep enabled, vgic_irq hangs but I believe it's
> an unrelated weirdness: if I introduce a separate lockdep warning for
> some made up locks, then the test passes again. So I'm sending this out
> now for discussion, and will investigate that one later.
> 
> I run the host with:
> 
> qemu-system-aarch64 -M virt,virtualization=true,gic-version=3 -m 2G -smp 8 -cpu max -append 'console=hvc0 root=/dev/vda rw' -kernel Image -nodefaults -chardev stdio,mux=on,id=virtiocon0,signal=off -device virtio-serial-device -device virtconsole,chardev=virtiocon0 -mon chardev=virtiocon0,mode=readline -device virtio-blk-device,drive=hd0 -drive format=raw,if=none,file=virt_root.bin,id=hd0 -nographic
> 
> Jean-Philippe Brucker (4):
>   KVM: arm64: vgic: Fix a circular locking issue
>   KVM: arm64: vgic: Wrap vgic_its_create() with config_lock
>   KVM: arm64: vgic: Fix locking comment
>   KVM: arm64: vgic: Fix a comment

Damn! Thought I had this sorted.

Thanks for taking a crack at this. I've looked it over a couple times,
and overall looks good.

For the series:

Reviewed-by: Oliver Upton <oliver.upton@linux.dev>

Once I get some free cycles this afternoon/evening I'll take the patches
for a spin.

-- 
Thanks,
Oliver

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