On Fri, Sep 08, 2023, Anish Moorthy wrote: > The relevant __gfn_to_pfn_memslot() calls in __kvm_faultin_pfn() > already use MEMSLOT_ACCESS_NONATOMIC_MAY_UPGRADE. --verbose > Signed-off-by: Anish Moorthy <amoorthy@xxxxxxxxxx> > --- > Documentation/virt/kvm/api.rst | 2 +- > arch/x86/kvm/Kconfig | 1 + > 2 files changed, 2 insertions(+), 1 deletion(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index c2eaacb6dc63..a74d721a18f6 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -7788,7 +7788,7 @@ error/annotated fault. > 7.35 KVM_CAP_USERFAULT_ON_MISSING > --------------------------------- > > -:Architectures: None > +:Architectures: x86 > :Returns: Informational only, -EINVAL on direct KVM_ENABLE_CAP. > > The presence of this capability indicates that userspace may set the > diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig > index ed90f148140d..11d956f17a9d 100644 > --- a/arch/x86/kvm/Kconfig > +++ b/arch/x86/kvm/Kconfig > @@ -49,6 +49,7 @@ config KVM > select INTERVAL_TREE > select HAVE_KVM_PM_NOTIFIER if PM > select KVM_GENERIC_HARDWARE_ENABLING > + select HAVE_KVM_USERFAULT_ON_MISSING Hmm, I vote to squash this patch with KVM: x86: Annotate -EFAULTs from kvm_handle_error_pfn() or rather, squash that code into this patch. Ditto for the ARM patches. Since we're making KVM_EXIT_MEMORY_FAULT informational-only for flows that KVM isn't committing to supporting, I think it makes sense to enable the arch specific paths that *need* to return KVM_EXIT_MEMORY_FAULT at the same time as the feature that adds the requirement. E.g. without HAVE_KVM_USERFAULT_ON_MISSING support, per the contract we are creating, it would be totally fine for KVM to not use KVM_EXIT_MEMORY_FAULT for the page fault paths. And that obviously has to be the case since KVM_CAP_MEMORY_FAULT_INFO is introduced before the arch code is enabled. But as of this path, KVM *must* return KVM_EXIT_MEMORY_FAULT, so we should make it impossible to do a straight revert of that dependency. That should also help with the changelogs, e.g. it'll give you a prompt for why only kvm_handle_error_pfn() is getting treatment.
