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Date:   Fri, 11 May 2018 11:40:19 -0400
From:   Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To:     Wanpeng Li <kernellwp@gmail.com>
Cc:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        Paolo Bonzini <pbonzini@redhat.com>,
        Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Tim Shearer <tshearer@advaoptical.com>,
        Liran Alon <liran.alon@oracle.com>
Subject: Re: [PATCH 0/3] KVM: VMX: Allow to disable ioport intercept per-VM
 by userspace
Message-ID: <20180511154019.GG27459@char.us.oracle.com>
References: <1523943962-25415-1-git-send-email-wanpengli@tencent.com>
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On Mon, Apr 16, 2018 at 10:45:59PM -0700, Wanpeng Li wrote:
> Tim Shearer reported that "There is a guest which is running a packet
> forwarding app based on the DPDK (dpdk.org). The packet receive routine
> writes to 0xc070 using glibc's "outw_p" function which does an additional
> write to I/O port 0x80. It does this write for every packet that's
> received, causing a flood of KVM userspace context switches". He uses
> mpstat to observe a CPU performing L2 packet forwarding on a pinned
> guest vCPU, the guest time is 95 percent when allowing I/O port 0x80
> bypass, however, it is 65.78 percent when I/O port 0x80 bypss is
> disabled.
> 
> This patchset introduces per-VM I/O permission bitmaps, the userspace
> can disable the ioport intercept when they are more concern the
> performance than the security.

Could you kindly also add:

Suggested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Thank you.