Re: [PATCH 14/14] KVM: x86: Add helpers to prepare kvm_run for userspace MMIO exit

[Sean Christopherson]

On Tue, Mar 03, 2026, Rick P Edgecombe wrote:
> On Mon, 2026-03-02 at 18:24 -0800, Sean Christopherson wrote:
> > Ooh, better idea.  Since TDX is the only direct user of
> > __kvm_prepare_emulated_mmio_exit() and it only supports lenths of 1, 2, 4, and 8,
> > kvm_prepare_emulated_mmio_exit() is the only path that actually needs to cap the
> > length.  Then the inner helper can assert a valid length.  Doesn't change anything
> > in practice, but I like the idea of making the caller be aware of the limitation
> > (even if that caller is itself a helper).
> 
> Seems ok and an improvement over the patch. But looking at the other callers,
> there is quite a bit of min(8u, len) logic spread around. Might be worth a wider
> cleanup someday.

LOL, "might".  :-)

Definitely a project for the future though, especially given how subtle and brittle
this all is.