linux-kernel - Re: [PATCH] LoongArch: KVM: Fully clear some registers when VM reboot

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Message-ID: <CAAhV-H51WRgk8Bs5dsF1LrgdaqL7dk9ioy7H79voZKapov9U2g@mail.gmail.com>
Date: Thu, 24 Apr 2025 14:53:12 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Bibo Mao <maobibo@...ngson.cn>
Cc: Tianrui Zhao <zhaotianrui@...ngson.cn>, WANG Xuerui <kernel@...0n.name>, kvm@...r.kernel.org, 
	loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] LoongArch: KVM: Fully clear some registers when VM reboot

Hi, Bibo,

On Thu, Apr 24, 2025 at 2:38 PM Bibo Mao <maobibo@...ngson.cn> wrote:
>
> Some registers such as LOONGARCH_CSR_ESTAT and LOONGARCH_CSR_GINTC
> are partly cleared with function _kvm_set_csr(). This comes from hardware
I cannot find the _kvm_set_csr() function, maybe it's a typo?
And the tile can be "LoongArch: KVM: Fully clear some CSRs when VM reboot"

Huacai

> specification, some bits are read only in VM mode, and however it can be
> written in host mode. So it is partly cleared in VM mode, and can be fully
> cleared in host mode.
>
> These read only bits show pending interrupt or exception status. When VM
> reset, the read-only bits should be cleared, otherwise vCPU will receive
> unknown interrupts in boot stage.
>
> Here registers LOONGARCH_CSR_ESTAT/LOONGARCH_CSR_GINTC are fully cleared
> in ioctl KVM_REG_LOONGARCH_VCPU_RESET vCPU reset path.
>
> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
> ---
>  arch/loongarch/kvm/vcpu.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
> index 8e427b379661..80b2316d6f58 100644
> --- a/arch/loongarch/kvm/vcpu.c
> +++ b/arch/loongarch/kvm/vcpu.c
> @@ -902,6 +902,14 @@ static int kvm_set_one_reg(struct kvm_vcpu *vcpu,
>                         vcpu->arch.st.guest_addr = 0;
>                         memset(&vcpu->arch.irq_pending, 0, sizeof(vcpu->arch.irq_pending));
>                         memset(&vcpu->arch.irq_clear, 0, sizeof(vcpu->arch.irq_clear));
> +
> +                       /*
> +                        * When vCPU reset, clear the ESTAT and GINTC registers
> +                        * And the other CSR registers are cleared with function
> +                        * _kvm_set_csr().
> +                        */
> +                       kvm_write_sw_gcsr(vcpu->arch.csr, LOONGARCH_CSR_GINTC, 0);
> +                       kvm_write_sw_gcsr(vcpu->arch.csr, LOONGARCH_CSR_ESTAT, 0);
>                         break;
>                 default:
>                         ret = -EINVAL;
>
> base-commit: 9d7a0577c9db35c4cc52db90bc415ea248446472
> --
> 2.39.3
>
>