From: Paolo Bonzini <pbonzini@redhat.com>
To: "Zhong, Yang" <yang.zhong@intel.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Cc: Stefan Hajnoczi <stefanha@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [Qemu-devel] The WCE issue in guest when i enable WCE in Qemu side.
Date: Tue, 23 Jul 2019 17:32:12 +0200 [thread overview]
Message-ID: <93e3762a-d906-6d6b-9a5f-7497af188f94@redhat.com> (raw)
In-Reply-To: <7A85DF989CAE8F42902CF7B31A7D94A1487D6D13@shsmsx102.ccr.corp.intel.com>
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
next prev parent reply other threads:[~2019-07-23 15:32 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-23 12:17 [Qemu-devel] The WCE issue in guest when i enable WCE in Qemu side Zhong, Yang
2019-07-23 15:32 ` Paolo Bonzini [this message]
2019-07-24 6:55 ` Yang Zhong
2019-07-24 8:57 ` Paolo Bonzini
2019-07-24 12:47 ` Yang Zhong
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