[PATCH] KVM: arm64: Fix hvhe and broken CNTVOFF_EL2

[Fuad Tabba]

Hi Mostafa,

On Thu, 6 Aug 2026 at 16:01, Mostafa Saleh <smostafa at google.com> wrote:
...
>  void __kvm_timer_set_cntvoff(u64 cntvoff)
>  {
> @@ -63,7 +64,7 @@ void __timer_enable_traps(struct kvm_vcpu *vcpu)
>          * Trap the virtual counter/timer if we have a broken cntvoff
>          * implementation.
>          */
> -       if (has_broken_cntvoff())
> +       if (has_broken_cntvoff() && hyp_timer_get_offset(vcpu_vtimer(vcpu)))
>                 set |= CNTHCTL_EL1TVT | CNTHCTL_EL1TVCT;

nit: the comment above could note the trap is now gated on a non-zero
virtual offset, to match timer_set_traps() on the VHE side (well...
maybe you don't want to _completely_ match _that_ comment, but you get
my drift ;)) .

Tested on QEMU with a forced has_broken_cntvoff(), then booted a
protected guest: without the patch it hits the UNDEF, with it the
guest boots.

Reviewed-by: Fuad Tabba <fuad.tabba at linux.dev>
Tested-by: Fuad Tabba < fuad.tabba at linux.dev>

Cheers,
/fuad


>
>         sysreg_clear_set(cnthctl_el2, clr, set);
> --
> 2.55.0.654.g21b8a5bc05-goog
>