On 01/29/2016 08:52 AM, Razvan Cojocaru wrote: > On 01/28/2016 11:47 PM, Tamas K Lengyel wrote: >> >> >> On Thu, Jan 28, 2016 at 2:05 PM, Razvan Cojocaru >> <rcojoc...@bitdefender.com <mailto:rcojoc...@bitdefender.com>> wrote: >> >> On 01/28/2016 10:09 PM, Tamas K Lengyel wrote: >> > On Thu, Jan 28, 2016 at 6:52 AM, Razvan Cojocaru >> > <rcojoc...@bitdefender.com <mailto:rcojoc...@bitdefender.com> >> <mailto:rcojoc...@bitdefender.com >> <mailto:rcojoc...@bitdefender.com>>> wrote: >> > >> > This patch pauses the domain for all writes through the 'ad' >> > pointer in monitor_domctl(), defers a domain_unpause() call until >> > after the CRs are updated for the MONITOR_EVENT_WRITE_CTRLREG >> > case, and makes sure that the domain is paused for both vm_event >> > enable and disable cases in vm_event_domctl(). >> > Thanks go to Andrew Cooper for his review and suggestions. >> > >> > >> > For vm_event_enable the domain is already paused by libxc before the >> > domctl is issued. I don't see a problem in doing another pause in Xen, >> > but given we have XSA-99, just doing this pause in Xen would not be >> > enough. So is it really necessary/fixes anything? >> >> This isn't about XSA-99, the problem here is related to my previous >> patch "x86 vm_event: reset monitor in vm_event_cleanup_domain()". While >> that improves matters and greatly reduces the chances of crashes due to >> hvm_msr_write_intercept() or hvm_set_crX() dereferencing a NULL >> v->arch.vm_event that's assumed to be OK, when the corresponding >> v->domain->arch.monitor is non-zero, the foolproof way is to make sure >> that functions such as vm_event_cleanup_domain() are always being called >> only while the domain has been paused. So there should be a >> domain_pause() call somewhere on the call path before that. >> >> >> Sure, but that's the disable case. I was only wondering about the enable >> case where the domain is already paused. > > Yes, for the disable case it is functionally redundant.
Sorry, I obviously meant "for the enable case". _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
