linux-kernel - Re: [PATCH v4 16/20] KVM: arm64: GICv4.1: Allow SGIs to switch between HW and SW interrupts

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Message-ID: <6798eb13-a7e9-2a92-91b2-9b657962ea79@huawei.com>
Date:   Thu, 20 Feb 2020 11:55:24 +0800
From:   Zenghui Yu <yuzenghui@...wei.com>
To:     Marc Zyngier <maz@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <kvmarm@...ts.cs.columbia.edu>, <kvm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Jason Cooper <jason@...edaemon.net>,
        Robert Richter <rrichter@...vell.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        Eric Auger <eric.auger@...hat.com>,
        "James Morse" <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>
Subject: Re: [PATCH v4 16/20] KVM: arm64: GICv4.1: Allow SGIs to switch
 between HW and SW interrupts

Hi Marc,

On 2020/2/14 22:57, Marc Zyngier wrote:
> In order to let a guest buy in the new, active-less SGIs, we
> need to be able to switch between the two modes.
> 
> Handle this by stopping all guest activity, transfer the state
> from one mode to the other, and resume the guest.
> 
> Signed-off-by: Marc Zyngier <maz@...nel.org>

[...]

> diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
> index 1bc09b523486..2c9fc13e2c59 100644
> --- a/virt/kvm/arm/vgic/vgic-v3.c
> +++ b/virt/kvm/arm/vgic/vgic-v3.c
> @@ -540,6 +540,8 @@ int vgic_v3_map_resources(struct kvm *kvm)
>   		goto out;
>   	}
>   
> +	if (kvm_vgic_global_state.has_gicv4_1)
> +		vgic_v4_configure_vsgis(kvm);
>   	dist->ready = true;
>   
>   out:

Is there any reason to invoke vgic_v4_configure_vsgis() here?
This is called on the first VCPU run, through kvm_vgic_map_resources().
Shouldn't the vSGI configuration only driven by a GICD_CTLR.nASSGIreq
writing (from guest, or from userspace maybe)?


Thanks,
Zenghui