On 2013-02-23 23:21, Jan Kiszka wrote: > On 2013-02-23 22:57, Jan Kiszka wrote: >> On 2013-02-23 22:45, Nadav Har'El wrote: >>> On Sat, Feb 23, 2013, Jan Kiszka wrote about "[PATCH] KVM: nVMX: Replace kvm_set_cr0 with vmx_set_cr0 in load_vmcs12_host_state": >>>> - kvm_set_cr0(vcpu, vmcs12->host_cr0); >>>> + vmx_set_cr0(vcpu, vmcs12->host_cr0); >>> >>> I don't remember now why I did this (and I'm not looking at the code), >>> but this you'll need to really test carefully, including >>> shadow-on-shadow mode (ept=0 in L0), to verify you're not missing any >>> important side-effect of kvm_set_cr0. >>> >>> Also, if I remember correctly, during nVMX's review, Avi Kivity asked >>> in several places that when I called vmx_set_cr0, I should instead call >>> kvm_set_cr0(), because it does some extra stuff and does some extra >>> checks. Hmm, see, see this: >>> http://markmail.org/message/hhidqyhbo2mrgxxc >>> >>> where Avi asked for the reverse patch you're attempting now. >> >> At least, kvm_set_cr0 can't be used as it assumes an otherwise >> consistent guest state and an explicitly initiated transition - which is >> naturally not the case while emulating a vmexit. >> >> However, there are some side effects that need a closer look, likely >> also in other places where vmx_set_cr0 is used directly. E.g. >> load_pdptrs. The lack of calling them on host->guest switch may explain >> the PAE issues you once saw with your nEPT implementation. >> >> OK, more work... > > Checked again, and the patch should be fine: load_pdptrs is executed by > kvm_set_cr3 later in this functions (same for prepare_vmcs02, so no > problem for PAE here), kvm_mmu_reset_context is even run explicitly and > clearing the async-pf queue makes no sense when leaving the guest (the > guest can't use it unless L1 is broken and passes this through). > However, we should clear the queue when leaving the host - separate patch. Thought about the async-pf thing again: It rather looks to me like the host does not have to worry about it at all. It's L1's job to either disable async-pf before entering L2 or trap PFs and handle paravirtual reasons before they hit L2. I don't see that KVM already does this, but I don't think that matters at this point. Jan
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