Messages in this thread | | | Date | Thu, 4 Apr 2024 09:45:27 -0700 | Subject | Re: [PATCH 01/16] KVM: x86/mmu: Exit to userspace with -EFAULT if private fault hits emulation | From | Sean Christopherson <> |
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On Fri, Mar 08, 2024, Yan Zhao wrote: > On Tue, Feb 27, 2024 at 06:41:32PM -0800, Sean Christopherson wrote: > > @@ -320,6 +328,11 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, > > else > > r = vcpu->arch.mmu->page_fault(vcpu, &fault); > > > > + if (r == RET_PF_EMULATE && fault.is_private) { > Should we just check VM type + RET_PF_EMULATE, and abort?
No, the goal here is purely to ensure that emulation is never triggered for private memory. Guarding against attempting emulation for a VM type that doesn't support emulation at all is something different.
And more concretely, as of this commit, all VM types that support private memory (i.e. SW_PROTECTED_VM) support emulation, just not for private memory.
> If r is RET_PF_EMULATE, and fault is caused by accesing a shared address, > the emulation code could still meet error if guest page table pages are in > private memory, right?
Yes, which is why I squeezed in a documentation update for v6.8 to make it super clear that SW_PROTECTED_VM is a development vehicle, i.e. that trying to use it to run a real VM is all but guaranteed to cause explosions.
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