On Mon, Jan 10, 2022 at 3:57 PM Jim Mattson <jmattson@xxxxxxxxxx> wrote: > > On Mon, Jan 10, 2022 at 3:07 PM Raghavendra Rao Ananta > <rananta@xxxxxxxxxx> wrote: > > > > On Fri, Jan 7, 2022 at 4:05 PM Jim Mattson <jmattson@xxxxxxxxxx> wrote: > > > > > > On Fri, Jan 7, 2022 at 3:43 PM Raghavendra Rao Ananta > > > <rananta@xxxxxxxxxx> wrote: > > > > > > > > Hi Reiji, > > > > > > > > On Thu, Jan 6, 2022 at 10:07 PM Reiji Watanabe <reijiw@xxxxxxxxxx> wrote: > > > > > > > > > > Hi Raghu, > > > > > > > > > > On Tue, Jan 4, 2022 at 11:49 AM Raghavendra Rao Ananta > > > > > <rananta@xxxxxxxxxx> wrote: > > > > > > > > > > > > Capture the start of the KVM VM, which is basically the > > > > > > start of any vCPU run. This state of the VM is helpful > > > > > > in the upcoming patches to prevent user-space from > > > > > > configuring certain VM features after the VM has started > > > > > > running. > > > > > > What about live migration, where the VM has already technically been > > > started before the first call to KVM_RUN? > > > > My understanding is that a new 'struct kvm' is created on the target > > machine and this flag should be reset, which would allow the VMM to > > restore the firmware registers. However, we would be running KVM_RUN > > for the first time on the target machine, thus setting the flag. > > So, you are right; It's more of a resume operation from the guest's > > point of view. I guess the name of the variable is what's confusing > > here. > > I was actually thinking that live migration gives userspace an easy > way to circumvent your restriction. You said, "This state of the VM is > helpful in the upcoming patches to prevent user-space from configuring > certain VM features after the VM has started running." However, if you > don't ensure that these VM features are configured the same way on the > target machine as they were on the source machine, you have not > actually accomplished your stated goal. > Isn't that up to the VMM to save/restore and validate the registers across migrations? Perhaps I have to re-word my intentions for the patch- userspace should be able to configure the registers before issuing the first KVM_RUN. Thanks, Raghavendra > > Thanks, > > Raghavendra
