On Fri, Jun 06, 2025 at 06:15:19AM -0700, Sean Christopherson wrote: > On Fri, Jun 06, 2025, Peter Zijlstra wrote: > > On Thu, Jun 05, 2025 at 10:19:41AM -0700, Josh Poimboeuf wrote: > > > diff --git a/arch/x86/entry/entry_64_fred.S b/arch/x86/entry/entry_64_fred.S > > > index 29c5c32c16c3..5d1eef193b79 100644 > > > --- a/arch/x86/entry/entry_64_fred.S > > > +++ b/arch/x86/entry/entry_64_fred.S > > > @@ -112,11 +112,12 @@ SYM_FUNC_START(asm_fred_entry_from_kvm) > > > push %rax /* Return RIP */ > > > push $0 /* Error code, 0 for IRQ/NMI */ > > > > > > - PUSH_AND_CLEAR_REGS clear_bp=0 unwind_hint=0 > > > + PUSH_AND_CLEAR_REGS clear_callee=0 unwind_hint=0 > > > movq %rsp, %rdi /* %rdi -> pt_regs */ > > > call __fred_entry_from_kvm /* Call the C entry point */ > > > - POP_REGS > > > - ERETS > > > + addq $C_PTREGS_SIZE, %rsp > > > + > > > + ALTERNATIVE "mov %rbp, %rsp", __stringify(ERETS), X86_FEATURE_FRED > > > > So... I was wondering.. do we actually ever need the ERETS? > > Yes, to unblock NMIs, because NMIs are blocked on VM-Exit due to NMI. Ah, bah, indeed! Shame.
