On Tue, Oct 23, 2012 at 5:07 PM, Jan Kiszka <jan.kis...@siemens.com> wrote: > On 2012-10-23 07:52, liu ping fan wrote: >> On Mon, Oct 22, 2012 at 6:40 PM, Avi Kivity <a...@redhat.com> wrote: >>> On 10/22/2012 11:23 AM, Liu Ping Fan wrote: >>>> The broken device state is caused by releasing local lock before acquiring >>>> big lock. To fix this issue, we have two choice: >>>> 1.use busy flag to protect the state >>>> The drawback is that we will introduce independent busy flag for each >>>> independent device's logic unit. >>>> 2.reload the device's state >>>> The drawback is if the call chain is too deep, the action to reload >>>> will >>>> touch each layer. Also the reloading means to recaculate the >>>> intermediate >>>> result based on device's regs. >>>> >>>> This patch adopt the solution 1 to fix the issue. >>> >>> Doesn't the nested mmio patch detect this? >>> >> It will only record and fix the issue on one thread. But guest can >> touch the emulated device on muti-threads. > > Sorry, what does that mean? A second VCPU accessing the device will > simply be ignored when it races with another VCPU? Specifically > Yes, just ignored. For device which support many logic in parallel, it should use independent busy flag for each logic
Regards, pingfan > + if (s->busy) { > + return; > > and > > + uint64_t ret = 0; > + > + if (s->busy) { > + return ret; > > is worrying me. > > Jan > > -- > Siemens AG, Corporate Technology, CT RTC ITP SDP-DE > Corporate Competence Center Embedded Linux