linux-kernel - Re: [PATCH v2 08/29] LoongArch: KVM: Implement vcpu handle exit interface

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Date:   Mon, 20 Feb 2023 18:46:38 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Tianrui Zhao <zhaotianrui@...ngson.cn>
Cc:     Huacai Chen <chenhuacai@...nel.org>,
        WANG Xuerui <kernel@...0n.name>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        Mark Brown <broonie@...nel.org>,
        Alex Deucher <alexander.deucher@....com>,
        Oliver Upton <oliver.upton@...ux.dev>, maobibo@...ngson.cn
Subject: Re: [PATCH v2 08/29] LoongArch: KVM: Implement vcpu handle exit
 interface

On 2/20/23 07:57, Tianrui Zhao wrote:
> +	if (ret == RESUME_GUEST)
> +		kvm_acquire_timer(vcpu);
> +
> +	if (!(ret & RESUME_HOST)) {
> +		_kvm_deliver_intr(vcpu);
> +		/* Only check for signals if not already exiting to userspace */
> +		if (signal_pending(current)) {
> +			run->exit_reason = KVM_EXIT_INTR;
> +			ret = (-EINTR << 2) | RESUME_HOST;
> +			++vcpu->stat.signal_exits;
> +			trace_kvm_exit(vcpu, KVM_TRACE_EXIT_SIGNAL);
> +		}
> +	}
> +
> +	if (ret == RESUME_GUEST) {
> +		trace_kvm_reenter(vcpu);
> +
> +		/*
> +		 * Make sure the read of VCPU requests in vcpu_reenter()
> +		 * callback is not reordered ahead of the write to vcpu->mode,
> +		 * or we could miss a TLB flush request while the requester sees
> +		 * the VCPU as outside of guest mode and not needing an IPI.
> +		 */
> +		smp_store_mb(vcpu->mode, IN_GUEST_MODE);
> +
> +		cpu = smp_processor_id();
> +		_kvm_check_requests(vcpu, cpu);
> +		_kvm_check_vmid(vcpu, cpu);
> +		vcpu->arch.host_eentry = csr_read64(LOONGARCH_CSR_EENTRY);
> +
> +		/*
> +		 * If FPU are enabled (i.e. the guest's FPU context
> +		 * is live), restore FCSR0.
> +		 */
> +		if (_kvm_guest_has_fpu(&vcpu->arch) &&
> +			read_csr_euen() & (CSR_EUEN_FPEN)) {
> +			kvm_restore_fcsr(&vcpu->arch.fpu);
> +		}
> +	}

Please avoid copying code from arch/mips/kvm since it's already pretty ugly.