linux-kernel - Re: [PATCH v12 16/31] LoongArch: KVM: Implement update VM id function

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Date:   Tue, 6 Jun 2023 09:13:16 +0800
From:   "bibo, mao" <maobibo@...ngson.cn>
To:     Tianrui Zhao <zhaotianrui@...ngson.cn>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Huacai Chen <chenhuacai@...nel.org>,
        WANG Xuerui <kernel@...0n.name>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        loongarch@...ts.linux.dev, Jens Axboe <axboe@...nel.dk>,
        Mark Brown <broonie@...nel.org>,
        Alex Deucher <alexander.deucher@....com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Xi Ruoyao <xry111@...111.site>
Subject: Re: [PATCH v12 16/31] LoongArch: KVM: Implement update VM id function

Reviewed-by: Bibo, Mao <maobibo@...ngson.cn>

在 2023/5/30 09:52, Tianrui Zhao 写道:
> Implement kvm check vmid and update vmid, the vmid should be checked before
> vcpu enter guest.
> 
> Signed-off-by: Tianrui Zhao <zhaotianrui@...ngson.cn>
> ---
>  arch/loongarch/kvm/vmid.c | 64 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 64 insertions(+)
>  create mode 100644 arch/loongarch/kvm/vmid.c
> 
> diff --git a/arch/loongarch/kvm/vmid.c b/arch/loongarch/kvm/vmid.c
> new file mode 100644
> index 000000000000..6fef81b28a48
> --- /dev/null
> +++ b/arch/loongarch/kvm/vmid.c
> @@ -0,0 +1,64 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2020-2023 Loongson Technology Corporation Limited
> + */
> +
> +#include <linux/kvm_host.h>
> +#include "trace.h"
> +
> +static void _kvm_update_vpid(struct kvm_vcpu *vcpu, int cpu)
> +{
> +	struct kvm_context *context;
> +	unsigned long vpid;
> +
> +	context = per_cpu_ptr(vcpu->kvm->arch.vmcs, cpu);
> +	vpid = context->vpid_cache + 1;
> +	if (!(vpid & vpid_mask)) {
> +		/* finish round of 64 bit loop */
> +		if (unlikely(!vpid))
> +			vpid = vpid_mask + 1;
> +
> +		/* vpid 0 reserved for root */
> +		++vpid;
> +
> +		/* start new vpid cycle */
> +		kvm_flush_tlb_all();
> +	}
> +
> +	context->vpid_cache = vpid;
> +	vcpu->arch.vpid = vpid;
> +}
> +
> +void _kvm_check_vmid(struct kvm_vcpu *vcpu, int cpu)
> +{
> +	struct kvm_context *context;
> +	bool migrated;
> +	unsigned long ver, old, vpid;
> +
> +	/*
> +	 * Are we entering guest context on a different CPU to last time?
> +	 * If so, the vCPU's guest TLB state on this CPU may be stale.
> +	 */
> +	context = per_cpu_ptr(vcpu->kvm->arch.vmcs, cpu);
> +	migrated = (vcpu->arch.last_exec_cpu != cpu);
> +	vcpu->arch.last_exec_cpu = cpu;
> +
> +	/*
> +	 * Check if our vpid is of an older version
> +	 *
> +	 * We also discard the stored vpid if we've executed on
> +	 * another CPU, as the guest mappings may have changed without
> +	 * hypervisor knowledge.
> +	 */
> +	ver = vcpu->arch.vpid & ~vpid_mask;
> +	old = context->vpid_cache  & ~vpid_mask;
> +	if (migrated || (ver != old)) {
> +		_kvm_update_vpid(vcpu, cpu);
> +		trace_kvm_vpid_change(vcpu, vcpu->arch.vpid);
> +	}
> +
> +	/* Restore GSTAT(0x50).vpid */
> +	vpid = (vcpu->arch.vpid & vpid_mask)
> +		<< CSR_GSTAT_GID_SHIFT;
> +	change_csr_gstat(vpid_mask << CSR_GSTAT_GID_SHIFT, vpid);
> +}