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From:   Peter Oskolkov <posk@google.com>
Date:   Thu, 21 Apr 2022 11:02:09 -0700
Message-ID: <CAPNVh5cQ6HhVqfuM7rhyK5RH6YYczkjAAgMwn7qHt8cbJneG_g@mail.gmail.com>
Subject: Re: [PATCH] KVM: x86: add HC_VMM_CUSTOM hypercall
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, kvm@vger.kernel.org,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H . Peter Anvin" <hpa@zytor.com>, linux-kernel@vger.kernel.org,
        Paul Turner <pjt@google.com>, Peter Oskolkov <posk@posk.io>
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On Thu, Apr 21, 2022 at 10:14 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 4/21/22 18:51, Peter Oskolkov wrote:
> > Allow kvm-based VMMs to request KVM to pass a custom vmcall
> > from the guest to the VMM in the host.
> >
> > Quite often, operating systems research projects and/or specialized
> > paravirtualized workloads would benefit from a extra-low-overhead,
> > extra-low-latency guest-host communication channel.
>
> You can use a memory page and an I/O port.  It should be as fast as a
> hypercall.  You can even change it to use ioeventfd if an asynchronous
> channel is enough, and then it's going to be less than 1 us latency.

Thank you for the suggestion. Let me try that.

Thanks,
Peter

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