Re: Will QEMU Support ARMv8.9-A Permission Indirection & Overlay Extensions?

[Peter Maydell]

On Wed, 13 Mar 2024 at 15:46, Xia Zhou <zhouxia_icsr@zju.edu.cn> wrote:
> Does QEMU-ARM have any plan to support the new permission indirection & 
> overlay extensions of ARMv8.9-A [1]? These features involve FEAT_S1PIE, 
> FEAT_S1POE, FEAT_S2PIE, and FEAT_S2POE. ARM64 Linux has patches for these 
> features [2] [3].

It's likely that we'll support them eventually, but we
usually lag behind the bleeding edge of the architecture
somewhat. I don't know if anybody has any concrete plan to
work on this specific feature.

(This feature is a bit awkward for QEMU because the indirection
isn't permitted to be cached in a TLB, and QEMU's core TCG design
is pretty heavily designed around permissions always being in the
TLB. I don't know if there's a nice way for us to implement it or
if we'd have to flush the TLB every time the guest changed the
overlay permissions...)

-- PMM