On Wed, 2021-02-17 at 18:37 +0100, Paolo Bonzini wrote: > On 17/02/21 18:29, Sean Christopherson wrote: > > All that being said, I'm pretty we can eliminate setting > > inject_page_fault dynamically. I think that would yield more > > maintainable code. Following these flows is a nightmare. The change > > itself will be scarier, but I'm pretty sure the end result will be a lot > > cleaner. I agree with that. > > I had a similar reaction, though my proposal was different. > > The only thing we're changing in complete_mmu_init is the page fault > callback for init_kvm_softmmu, so couldn't that be the callback directly > (i.e. something like context->inject_page_fault = > kvm_x86_ops.inject_softmmu_page_fault)? And then adding is_guest_mode > to the conditional that is already in vmx_inject_page_fault_nested and > svm_inject_page_fault_nested. I was thinking about this a well, I tried to make an as simple as possible solution that doesn't make things worse. > > That said, I'm also rusty on _why_ this code is needed. Why isn't it > enough to inject the exception normally, and let > nested_vmx_check_exception decide whether to inject a vmexit to L1 or an > exception into L2? > > Also, bonus question which should have been in the 5/7 changelog: are > there kvm-unit-tests testcases that fail with npt=0, and if not could we > write one? [Answer: the mode_switch testcase fails, but I haven't > checked why]. I agree with all of this. I'll see why this code is needed (it is needed, since I once removed it accidentaly on VMX, and it broke nesting with ept=0, in exact the same way as it was broken on AMD). I''l debug this a bit to see if I can make it work as you suggest. Best regards, Maxim Levitsky > > > Paolo >
