On Tue, Jul 30, 2024, Paolo Bonzini wrote: > On 7/27/24 01:51, Sean Christopherson wrote: > > Add a kvm_follow_pfn() wrapper, kvm_lookup_pfn(), to allow looking up a > > gfn=>pfn mapping without the caller getting a reference to any underlying > > page. The API will be used in flows that want to know if a gfn points at > > a valid pfn, but don't actually need to do anything with the pfn. > > Can you rename the function kvm_gfn_has_pfn(), or kvm_gfn_can_be_mapped(), > and make it return a bool? Heh, sure. I initially planned on having it return a bool, but I couldn't figure out a name, mainly because the kernel's pfn_valid() makes things like kvm_gfn_has_valid_pfn() confusing/misleading :-( > (As an aside, I wonder if reexecute_instruction() could just use > kvm_is_error_hva(kvm_vcpu_gfn_to_hva(vcpu, gpa_to_gfn(gpa)) instead of going > all the way to a pfn. But it's ok to be more restrictive). Heh #2, I wondered the same thing. I think it would work? Verifying that there's a usable pfn also protects against retrying an access that hit -EHWPOISON, but I'm prety sure that would require a rare race, and I don't think it could result in the guest being put into an infinite loop.
