2017-11-09 19:05 GMT+08:00 Paolo Bonzini <pbonzini@xxxxxxxxxx>: > On 09/11/2017 11:47, Wanpeng Li wrote: >> 2017-11-09 18:40 GMT+08:00 Paolo Bonzini <pbonzini@xxxxxxxxxx>: >>> On 09/11/2017 01:37, Wanpeng Li wrote: >>>> 2017-11-09 5:47 GMT+08:00 Jim Mattson <jmattson@xxxxxxxxxx>: >>>>> I realize now that there are actually many other problems with >>>>> deferring some control field checks to the hardware VM-entry of >>>>> vmcs02. When there is an invalid control field, the vCPU should just >>>>> fall through to the next instruction, without any state modifiation >>>>> other than the ALU flags and the VM-instruction error field of the >>>>> current VMCS. However, in preparation for the hardware VM-entry of >>>>> vmcs02, we have already changed quite a bit of the vCPU state: the >>>>> MSRs on the VM-entry MSR-load list, DR7, IA32_DEBUGCTL, the entire >>>>> FLAGS register, etc. All of these changes should be undone, and we're >>>>> not prepared to do that. (For instance, what was the old DR7 value >>>>> that needs to be restored?) >>>> I didn't observe real issue currently, and I hope this patchset can >>>> catch the upcoming merge window. Then we can dig more into your >>>> concern. >>> >>> Can any of you write a simple testcase for just one bug (e.g. DR7)? >> >> Jim you can have a try for your concern, I have already tried tons of >> stress testing and didn't observe any issue. > > You need to craft a testcase for kvm-unit-tests. No stress testing will > find an issue. > > Your patch is fine, but Jim is saying that we cannot really skip the > check for invalid control fields. It's a more general issue that can be > fixed by adding explicit checks in KVM. Fair enough. I will find time to do this recently. I guess Radim can apply the whole patchset today. :) Regards, Wanpeng Li
