Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH] kvm: add capability for halt polling
To:     Jon Cargille <jcargill@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>
Cc:     David Matlack <dmatlack@google.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20200417221446.108733-1-jcargill@google.com>
 <87d083td9f.fsf@vitty.brq.redhat.com>
 <CANxmayg3ML5_w=pY3=x7_TLOqawojxYGbqMLrXJn+r0b_gvWgA@mail.gmail.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <02039a7b-01b4-ea5c-bd73-100ea753bf5e@redhat.com>
Date:   Mon, 20 Apr 2020 23:09:47 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.6.0
MIME-Version: 1.0
In-Reply-To: <CANxmayg3ML5_w=pY3=x7_TLOqawojxYGbqMLrXJn+r0b_gvWgA@mail.gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 20/04/20 20:47, Jon Cargille wrote:
>> Is it safe to allow any value from userspace here or would it maybe make
>> sense to only allow [0, global halt_poll_ns]?
> I believe that any value is safe; a very large value effectively disables
> halt-polling, which is equivalent to setting a value of zero to explicitly
> disable it, which is legal.

Doesn't a large value make KVM poll all the time?  But you could do that
just by running "for (;;)" so there's no reason to limit the parameter.

Paolo