From: Paolo Bonzini <pbonzini@redhat.com>
To: Anastassios Nanos <ananos@nubificus.co.uk>,
Marc Zyngier <maz@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Wanpeng Li <wanpengli@tencent.com>,
kvm@vger.kernel.org, Catalin Marinas <catalin.marinas@arm.com>,
Joerg Roedel <joro@8bytes.org>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Sean Christopherson <sean.j.christopherson@intel.com>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Borislav Petkov <bp@alien8.de>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Will Deacon <will@kernel.org>,
kvmarm@lists.cs.columbia.edu, Jim Mattson <jmattson@google.com>
Subject: Re: [PATCH 0/2] Expose KVM API to Linux Kernel
Date: Mon, 18 May 2020 13:18:23 +0200 [thread overview]
Message-ID: <760e0927-d3a7-a8c6-b769-55f43a65e095@redhat.com> (raw)
In-Reply-To: <CALRTab90UyMq2hMxCdCmC3GwPWFn2tK_uKMYQP2YBRcHwzkEUQ@mail.gmail.com>
On 18/05/20 10:45, Anastassios Nanos wrote:
> Being in the kernel saves us from doing unneccessary mode switches.
> Of course there are optimizations for handling I/O on QEMU/KVM VMs
> (virtio/vhost), but essentially what happens is removing mode-switches (and
> exits) for I/O operations -- is there a good reason not to address that
> directly? a guest running in the kernel exits because of an I/O request,
> which gets processed and forwarded directly to the relevant subsystem *in*
> the kernel (net/block etc.).
In high-performance configurations, most of the time virtio devices are
processed in another thread that polls on the virtio rings. In this
setup, the rings are configured to not cause a vmexit at all; this has
much smaller latency than even a lightweight (kernel-only) vmexit,
basically corresponding to writing an L1 cache line back to L2.
Paolo
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next prev parent reply other threads:[~2020-05-18 11:18 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-18 6:58 [PATCH 0/2] Expose KVM API to Linux Kernel Anastassios Nanos
2020-05-18 6:58 ` [PATCH 1/2] KVMM: export needed symbols Anastassios Nanos
2020-05-18 7:41 ` Marc Zyngier
2020-05-18 7:01 ` [PATCH 2/2] KVMM: Memory and interface related changes Anastassios Nanos
2020-05-18 6:59 ` Anastassios Nanos
2020-05-18 9:13 ` kbuild test robot
2020-05-18 9:28 ` kbuild test robot
2020-05-18 10:16 ` kbuild test robot
2020-05-18 7:50 ` [PATCH 0/2] Expose KVM API to Linux Kernel Marc Zyngier
[not found] ` <CALRTab90UyMq2hMxCdCmC3GwPWFn2tK_uKMYQP2YBRcHwzkEUQ@mail.gmail.com>
2020-05-18 11:18 ` Paolo Bonzini [this message]
2020-05-18 11:34 ` Maxim Levitsky
2020-05-18 11:51 ` Paolo Bonzini
2020-05-18 12:12 ` Maxim Levitsky
2020-05-18 20:45 ` Andy Lutomirski
2020-05-18 8:42 ` Thomas Gleixner
[not found] ` <CALRTab-mEYtRG4zQbSGoAri+jg8xNL-imODv=MWE330Hkt_t+Q@mail.gmail.com>
2020-05-18 9:18 ` Vitaly Kuznetsov
2020-05-18 9:38 ` Thomas Gleixner
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