Sean Christopherson <[email protected]> writes: > On Fri, Jun 05, 2020 at 01:59:05PM +0200, Vitaly Kuznetsov wrote: >> Introduce vmx_handle_memory_failure() as an interim solution. > > Heh, "interim". I'll take the over on that :-D. >
We just need a crazy but real use-case to start acting :-) >> Note, nested_vmx_get_vmptr() now has three possible outcomes: OK, PF, >> KVM_EXIT_INTERNAL_ERROR and callers need to know if userspace exit is >> needed (for KVM_EXIT_INTERNAL_ERROR) in case of failure. We don't seem >> to have a good enum describing this tristate, just add "int *ret" to >> nested_vmx_get_vmptr() interface to pass the information. On a loosely related note, while writing this patch I was struggling with our exit handlers calling convention (that the return value is '1' - return to the guest, '0' - return to userspace successfully, '< 0' - return to userspace with an error). This is intertwined with normal int/bool functions and make it hard to read. At the very minimum we can introduce an enum for 0/1 return values from exit handlers. Or, maybe, we can introduce KVM_REQ_USERSPACE_EXIT/KVM_REQ_INTERNAL_ERROR/.. and make all the exit handlers normal functions returning 0/error? >> >> Reported-by: [email protected] >> Suggested-by: Sean Christopherson <[email protected]> >> Signed-off-by: Vitaly Kuznetsov <[email protected]> >> --- > > ... > >> +/* >> + * Handles kvm_read/write_guest_virt*() result and either injects #PF or >> returns >> + * KVM_EXIT_INTERNAL_ERROR for cases not currently handled by KVM. Return >> value >> + * indicates whether exit to userspace is needed. >> + */ >> +int vmx_handle_memory_failure(struct kvm_vcpu *vcpu, int r, >> + struct x86_exception *e) >> +{ >> + if (r == X86EMUL_PROPAGATE_FAULT) { >> + kvm_inject_emulated_page_fault(vcpu, e); >> + return 1; >> + } >> + >> + /* >> + * In case kvm_read/write_guest_virt*() failed with X86EMUL_IO_NEEDED >> + * while handling a VMX instruction KVM could've handled the request > > A nit similar to your observation on the shortlog, this isn't limited to VMX > instructions. > Yea, it all started with nested_vmx_get_vmptr() then Paolo discovered vmwrite/vmread/vmptrst/invept/invvpid and then I discovered invpcid but forgot to update the comment ... >> + * correctly by exiting to userspace and performing I/O but there >> + * doesn't seem to be a real use-case behind such requests, just return >> + * KVM_EXIT_INTERNAL_ERROR for now. >> + */ >> + vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; >> + vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION; >> + vcpu->run->internal.ndata = 0; >> + >> + return 0; >> +} > -- Vitaly
