Re: [PATCH v2 0/2] KVM: VMX: Clean up IRQ/NMI handling

From: Paolo Bonzini
Date: Tue Sep 22 2020 - 09:38:57 EST

On 15/09/20 21:15, Sean Christopherson wrote:
> Clean up KVM's handling of IRQ and NMI exits to move the invocation of the
> IRQ handler to a standalone assembly routine, and to then consolidate the
> NMI handling to use the same indirect call approach instead of using INTn.
> The IRQ cleanup was suggested by Josh Poimboeuf in the context of a false
> postive objtool warning[*]. I believe Josh intended to use UNWIND hints
> instead of trickery to avoid objtool complaints. I opted for trickery in
> the form of a redundant, but explicit, restoration of RSP after the hidden
> IRET. AFAICT, there are no existing UNWIND hints that would let objtool
> know that the stack is magically being restored, and adding a new hint to
> save a single MOV <reg>, <reg> instruction seemed like overkill.
> The NMI consolidation was loosely suggested by Andi Kleen. Andi's actual
> suggestion was to export and directly call the NMI handler, but that's a
> more involved change (unless I'm misunderstanding the wants of the NMI
> handler), whereas piggybacking the IRQ code is simple and seems like a
> worthwhile intermediate step.
> Sean Christopherson (2):
> KVM: VMX: Move IRQ invocation to assembly subroutine
> KVM: VMX: Invoke NMI handler via indirect call instead of INTn
> arch/x86/kvm/vmx/vmenter.S | 34 +++++++++++++++++++++
> arch/x86/kvm/vmx/vmx.c | 61 +++++++++++---------------------------
> 2 files changed, 51 insertions(+), 44 deletions(-)

Queued, thanks.