On Sat, Dec 11, 2021 at 10:01 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > On 12/11/21 01:11, Paolo Bonzini wrote: > > Yeah, vmx_prepare_switch_to_guest() doesn't update HOST_CR3 if no > > preemption happens from one call of vcpu_enter_guest() to the next > > (preemption would cause a call to kvm_arch_vcpu_put and from there to > > vmx_prepare_switch_to_host, which clears vmx->guest_state_loaded). > > > > During that time an MM switch is bumping the PCID; I would have expected > > any such flush to require a preemption (in order to reach e.g. > > switch_mm_irqs_off), but that must be wrong. In the splat below in fact > > you can see that the values are 0x60674f2005 (RAX) and 0x60674f2006 (RCX > > and CR3). > > As Jiangshan said, the PCID is bumped while L2 runs, and is stale when > switching back to the vmcs01. That indeed is compatible with a > preemption. There should definitely be a comment in > vmx_prepare_switch_to_guest() that points to vmx_sync_vmcs_host_state(). > I think it would be better to rename vmx_set_host_fs_gs() to vmx_set_vmcs_host_state() and it also handles for HOST_CR3. And both vmx_prepare_switch_to_guest() and vmx_sync_vmcs_host_state() will call vmx_set_vmcs_host_state(). Thanks Lai
