From: Peng Hao <peng.hao2@zte.com.cn>
To: pbonzini@redhat.com, rkrcmar@redhat.com
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
zhong.weidong@zte.com.cn, wanpeng.li@hotmail.com,
Peng Hao <peng.hao2@zte.com.cn>
Subject: [PATCH V4 0/2] introduce coalesced pio support
Date: Fri, 31 Aug 2018 00:17:19 +0800 [thread overview]
Message-ID: <1535645841-111837-1-git-send-email-peng.hao2@zte.com.cn> (raw)
Coalesced pio is base on coalesced mmio and can be used for some port
like rtc port, pci-host config port, virtio-pci config port and so on.
Specially in case of rtc as coalesced pio, some versions of windows guest
access rtc frequently because of rtc as system tick. guest access rtc like
this: write register index to 0x70, then write or read data from 0x71.
writing 0x70 port is just as index and do nothing else. So we can use
coalesced pio to handle this scene to reduce VM-EXIT time.
When it starts and closes the virtual machine, it will access pci-host config
port or virtio-pci config port frequently. So setting these port as
coalesced pio can reduce startup and shutdown time. In qemu I just realize
piixfx's pci-host, it is convenient for other pci-host type implementations.
without my patch, get the vm-exit time of accessing rtc 0x70 and piix 0xcf8
using perf tools: (guest OS : windows 7 64bit)
IO Port Access Samples Samples% Time% Min Time Max Time Avg time
0x70:POUT 86 30.99% 74.59% 9us 29us 10.75us (+- 3.41%)
0xcf8:POUT 1119 2.60% 2.12% 2.79us 56.83us 3.41us (+- 2.23%)
with my patch
IO Port Access Samples Samples% Time% Min Time Max Time Avg time
0x70:POUT 106 32.02% 29.47% 0us 10us 1.57us (+- 7.38%)
0xcf8:POUT 1065 1.67% 0.28% 0.41us 65.44us 0.66us (+- 10.55%)
Peng Hao (2):
kvm/x86 : add coalesced pio support
kvm/x86 : add document for coalesced pio
Documentation/virtual/kvm/00-INDEX | 2 ++
Documentation/virtual/kvm/coalesced-pio.txt | 15 ++++++++++++++
include/uapi/linux/kvm.h | 11 +++++++++--
virt/kvm/coalesced_mmio.c | 12 +++++++++---
virt/kvm/kvm_main.c | 2 ++
5 files changed, 37 insertions(+), 5 deletions(-)
create mode 100644 Documentation/virtual/kvm/coalesced-pio.txt
--
1.8.3.1
next reply other threads:[~2018-08-30 16:17 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-30 16:17 Peng Hao [this message]
2018-08-30 16:17 ` [PATCH V4 1/2] kvm/x86 : add coalesced pio support Peng Hao
2018-08-30 16:17 ` [PATCH V4 2/2] kvm/x86 : add document for coalesced pio Peng Hao
2018-10-12 15:27 ` Stefan Hajnoczi
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