linux-kernel - Re: [PATCH 0/3] KVM: VMX: Allow to disable ioport intercept per-VM by userspace

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Date:   Sat, 12 May 2018 09:03:02 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Tim Shearer <tshearer@...aoptical.com>,
        Liran Alon <liran.alon@...cle.com>
Subject: Re: [PATCH 0/3] KVM: VMX: Allow to disable ioport intercept per-VM by userspace

2018-05-11 23:40 GMT+08:00 Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>:
> 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@...cle.com>

Yeah, both you and Liran give the original idea. :) Tim and Liran, any
review for the patchset?

Regards,
Wanpeng Li