Re: [PATCH v4 0/9] KVM: arm64: Initial host support for the Apple M1

[Alexandru Elisei <alexandru.elisei@arm.com>]

Hi Marc,

On 6/1/21 11:39 AM, Marc Zyngier wrote:
> This is a new version of the series previously posted at [3], reworking
> the vGIC and timer code to cope with the M1 braindead^Wamusing nature.
>
> Hardly any change this time around, mostly rebased on top of upstream
> now that the dependencies have made it in.
>
> Tested with multiple concurrent VMs running from an initramfs.
>
> Until someone shouts loudly now, I'll take this into 5.14 (and in
> -next from tomorrow).

I am not familiar with irqdomains or with the irqchip infrastructure, so I can't
really comment on patch #8.

I tried testing this with a GICv3 by modifying the driver to set
no_hw_deactivation and no_maint_irq_mask:

diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c
index 340c51d87677..d0c6f808d7f4 100644
--- a/arch/arm64/kvm/vgic/vgic-init.c
+++ b/arch/arm64/kvm/vgic/vgic-init.c
@@ -565,8 +565,10 @@ int kvm_vgic_hyp_init(void)
        if (ret)
                return ret;
 
+       /*
        if (!has_mask)
                return 0;
+               */
 
        ret = request_percpu_irq(kvm_vgic_global_state.maint_irq,
                                 vgic_maintenance_handler,
diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index 453fc425eede..9ce4dee20655 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -1850,6 +1850,12 @@ static void __init gic_of_setup_kvm_info(struct device_node
*node)
        if (!ret)
                gic_v3_kvm_info.vcpu = r;
 
+       gic_v3_kvm_info.no_hw_deactivation = true;
+       gic_v3_kvm_info.no_maint_irq_mask = true;
+
+       vgic_set_kvm_info(&gic_v3_kvm_info);
+       return;
+
        gic_v3_kvm_info.has_v4 = gic_data.rdists.has_vlpis;
        gic_v3_kvm_info.has_v4_1 = gic_data.rdists.has_rvpeid;
        vgic_set_kvm_info(&gic_v3_kvm_info);

Kept the maintenance irq ID so the IRQ gets enabled at the Redistributor level. I
don't know if I managed to break something with those changes, but when testing on
the model and on a rockpro64 (with the patches cherry-picked on top of v5.13-rc7)
I kept seeing rcu stalls. I assume I did something wrong.

Thanks,

Alex

>
> * From v3 [3]:
>   - Rebased on 5.13-rc4 to match the kvmarm/next base
>   - Moved stuff from patch #7 to its logical spot in patch #8
>   - Changed the include/linux/irqchip/arm-vgic-info.h guard
>   - Collected RBs from Alex, with thanks
>
> * From v2 [2]:
>   - Rebased on 5.13-rc1
>   - Fixed a couple of nits in the GIC registration code
>
> * From v1 [1]:
>   - Rebased on Hector's v4 posting[0]
>   - Dropped a couple of patches that have been merged in the above series
>   - Fixed irq_ack callback on the timer path
>
> [0] https://lore.kernel.org/r/20210402090542.131194-1-marcan@marcan.st
> [1] https://lore.kernel.org/r/20210316174617.173033-1-maz@kernel.org
> [2] https://lore.kernel.org/r/20210403112931.1043452-1-maz@kernel.org
> [3] https://lore.kernel.org/r/20210510134824.1910399-1-maz@kernel.org
>
> Marc Zyngier (9):
>   irqchip/gic: Split vGIC probing information from the GIC code
>   KVM: arm64: Handle physical FIQ as an IRQ while running a guest
>   KVM: arm64: vgic: Be tolerant to the lack of maintenance interrupt
>     masking
>   KVM: arm64: vgic: Let an interrupt controller advertise lack of HW
>     deactivation
>   KVM: arm64: vgic: move irq->get_input_level into an ops structure
>   KVM: arm64: vgic: Implement SW-driven deactivation
>   KVM: arm64: timer: Refactor IRQ configuration
>   KVM: arm64: timer: Add support for SW-based deactivation
>   irqchip/apple-aic: Advertise some level of vGICv3 compatibility
>
>  arch/arm64/kvm/arch_timer.c            | 162 +++++++++++++++++++++----
>  arch/arm64/kvm/hyp/hyp-entry.S         |   6 +-
>  arch/arm64/kvm/vgic/vgic-init.c        |  36 +++++-
>  arch/arm64/kvm/vgic/vgic-v2.c          |  19 ++-
>  arch/arm64/kvm/vgic/vgic-v3.c          |  19 ++-
>  arch/arm64/kvm/vgic/vgic.c             |  14 +--
>  drivers/irqchip/irq-apple-aic.c        |   9 ++
>  drivers/irqchip/irq-gic-common.c       |  13 --
>  drivers/irqchip/irq-gic-common.h       |   2 -
>  drivers/irqchip/irq-gic-v3.c           |   6 +-
>  drivers/irqchip/irq-gic.c              |   6 +-
>  include/kvm/arm_vgic.h                 |  41 +++++--
>  include/linux/irqchip/arm-gic-common.h |  25 +---
>  include/linux/irqchip/arm-vgic-info.h  |  45 +++++++
>  14 files changed, 299 insertions(+), 104 deletions(-)
>  create mode 100644 include/linux/irqchip/arm-vgic-info.h
>