[PATCH] kvm: arm/arm64 : fix vm's hanging at startup time

On 16/11/18 00:23, peng.hao2 at zte.com.cn wrote:

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Hi,

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When virtual machine starts, hang up.

I take it you mean the *guest* hangs? Because it doesn't get a timer
interrupt?

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The kernel version of guest
is 4.16. Host support vgic_v3.

Your host kernel is something recent, I guess?

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It was mainly due to the incorrect vgic_irq's(intid=27) group value
during injection interruption. when kvm_vgic_vcpu_init is called,
dist is not initialized at this time. Unable to get vgic V3 or V2
correctly, so group is not set.

Mmh, that shouldn't happen with (v)GICv3. Do you use QEMU (which
version?) or some other userland tool?

QEMU emulator version 3.0.50 .

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group is setted to 1 when vgic_mmio_write_group is invoked at some
time.
when irq->group=0 (intid=27), No ICH_LR_GROUP flag was set and
interrupt injection failed.

Signed-off-by: Peng Hao <redacted>
---
  virt/kvm/arm/vgic/vgic-v3.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
index 9c0dd23..d101000 100644
--- a/virt/kvm/arm/vgic/vgic-v3.c
+++ b/virt/kvm/arm/vgic/vgic-v3.c

@@ -198,7 +198,7 @@ void vgic_v3_populate_lr(struct kvm_vcpu *vcpu,

struct vgic_irq *irq, int lr) if (vgic_irq_is_mapped_level(irq) &&
(val & ICH_LR_PENDING_BIT)) irq->line_level = false;

-    if (irq->group)
+    if (model == KVM_DEV_TYPE_ARM_VGIC_V3)

This is not the right fix, not only because it basically reverts the
GICv3 part of 87322099052 (KVM: arm/arm64: vgic: Signal IRQs using
their configured group).

Can you try to work out why kvm_vgic_vcpu_init() is apparently called
before dist->vgic_model is set, also what value it has?
If I understand the code correctly, that shouldn't happen for a GICv3.

Even if the value of  group is correctly assigned in kvm_vgic_vcpu_init, the group is then written 0 through vgic_mmio_write_group.
  If the interrupt comes at this time, the interrupt injection fails.

Does that mean that the guest is configuring its interrupts as Group0? 
That sounds wrong, Linux should configure all it's interrupts as 
non-secure group1.

-- 
Julien Thierry