KVM: arm64: Skip instruction after emulating write to TCR_EL1

Whelp, this is embarrassing. Since commit 082fdfd13841 ("KVM: arm64:
Prevent guests from enabling HA/HD on Ampere1") KVM traps writes to
TCR_EL1 on AmpereOne to work around an erratum in the unadvertised
HAFDBS implementation, preventing the guest from enabling the feature.
Unfortunately, I failed virtualization 101 when working on that change,
and forgot to advance PC after instruction emulation.

Do the right thing and skip the MSR instruction after emulating the
write.

Fixes: 082fdfd13841 ("KVM: arm64: Prevent guests from enabling HA/HD on Ampere1")
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230728000824.3848025-1-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 4bddb85..34f222a 100644 (file)
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -457,6 +457,7 @@ static bool handle_ampere1_tcr(struct kvm_vcpu *vcpu)
         */
        val &= ~(TCR_HD | TCR_HA);
        write_sysreg_el1(val, SYS_TCR);
+       __kvm_skip_instr(vcpu);
        return true;
 }