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Re: [Qemu-devel] The WCE issue in guest when i enable WCE in Qemu side.
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From: |
Paolo Bonzini |
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Subject: |
Re: [Qemu-devel] The WCE issue in guest when i enable WCE in Qemu side. |
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Date: |
Tue, 23 Jul 2019 17:32:12 +0200 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 |
On 23/07/19 14:17, Zhong, Yang wrote:
> When I set config-wce=true or false, the below value never change
> root@unicorn ~ # cat /sys/block/vda/cache_type
> write back
> root@unicorn ~ # cat /sys/block/vda/device/features
> 0010 0010 0110 0110 0000 0000 0000 1000 1000 0000 0000 0000 0000 0000 0000
> 0000
> From left to right, bit 11=0, which show there is no WCE feature in
> vhost-user-blk device.
Does your backend expose the feature in the VHOST_GET_FEATURES message?
> I also did one simple patch to add config_wce value into s->blkcfg.wce, but
> the result is same.
config_wce doesn't tell you if you are in writeback or writethrough
mode, it tells you if you can *change* the mode.
If your backend did not expose the feature, try changing that and then
"echo write through > /sys/block/vda/cache_type" should work?
Paolo