Hi Yifan,

The feature is unfortunately only supported in gem5 by the GICv3 implementation.
Could you try to run your software stack with GICv3 instead?

Kind Regards

Giacomo

From: Yifan Tan <tanyi...@sjtu.edu.cn>
Date: Saturday, 16 July 2022 at 12:17
To: gem5-users@gem5.org <gem5-users@gem5.org>
Subject: [gem5-users] GEM5 Arm VGIC does not support 'HW' List Register feature

Hi all,

I tried running a KVM guest on Arm GEM5 Linux, but GEM5 panicked at 
https://gem5.googlesource.com/public/gem5/+/refs/heads/stable/src/dev/arm/vgic.cc#126.

The comment above this `panic` said KVM does not use auto-EOI of HW interrupts 
via real GIC.

However, in later Linux version, function `kvm_vgic_map_phys_irq` would set the 
HW bit to 1, as in 
https://gem5.googlesource.com/arm/linux/+/refs/heads/gem5/v4.14/virt/kvm/arm/vgic/vgic.c#406.

I've tested gem5/v4.3, which is the oldest version branch of repo arm/linux in 
gem5 source. In 
https://gem5.googlesource.com/arm/linux/+/refs/heads/gem5/v4.3/virt/kvm/arm/vgic.c#1778,
 the code does not explicitly set HW to 1, but the virtual irq is also mapped 
to physical irq, and the GEM5 would panic at the same place.

Does this mean I could only boot host Linux of very old version without 
`kvm_vgic_map_phys_irq`? I wonder that, without the support of 
`kvm_vgic_map_phys_irq`, the performance would suffer. The EOI of virtual irq 
would bring about an additional VM exit.

Thanks!

Yifan Tan
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