linux-kernel - Re: [PATCH v3 11/19] RISC-V: KVM: Implement VMID allocator

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Message-ID: <21bdde39-8d33-6aae-e729-476ce11406a3@redhat.com>
Date:   Mon, 5 Aug 2019 18:03:00 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Anup Patel <Anup.Patel@....com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Radim K <rkrcmar@...hat.com>
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Atish Patra <Atish.Patra@....com>,
        Alistair Francis <Alistair.Francis@....com>,
        Damien Le Moal <Damien.LeMoal@....com>,
        Christoph Hellwig <hch@...radead.org>,
        Anup Patel <anup@...infault.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 11/19] RISC-V: KVM: Implement VMID allocator

On 05/08/19 15:43, Anup Patel wrote:
> +	spin_lock(&vmid_lock);
> +
> +	/*
> +	 * We need to re-check the vmid_version here to ensure that if
> +	 * another vcpu already allocated a valid vmid for this vm.
> +	 */
> +	if (!kvm_riscv_stage2_vmid_ver_changed(vmid)) {
> +		spin_unlock(&vmid_lock);
> +		return;
> +	}
> +
> +	/* First user of a new VMID version? */
> +	if (unlikely(vmid_next == 0)) {
> +		WRITE_ONCE(vmid_version, READ_ONCE(vmid_version) + 1);
> +		vmid_next = 1;
> +
> +		/*
> +		 * On SMP, we know no other CPUs can use this CPU's or
> +		 * each other's VMID after forced exit returns since the
> +		 * vmid_lock blocks them from re-entry to the guest.
> +		 */
> +		spin_unlock(&vmid_lock);
> +		kvm_flush_remote_tlbs(vcpu->kvm);
> +		spin_lock(&vmid_lock);

This comment is not true anymore, so this "if" should become a "while".

Paolo