arm64: KVM: VHE: reset PSTATE.PAN on entry to EL2

SCTLR_EL2.SPAN bit controls what happens with the PSTATE.PAN bit on an
exception. However, this bit has no effect on the PSTATE.PAN when
HCR_EL2.E2H or HCR_EL2.TGE is unset. Thus when VHE is used and
exception taken from a guest PSTATE.PAN bit left unchanged and we
continue with a value guest has set.

To address that always reset PSTATE.PAN on entry from EL1.

Fixes: 1f364c8 ("arm64: VHE: Add support for running Linux in EL2 mode")

Signed-off-by: Vladimir Murzin <[email protected]>
Reviewed-by: James Morse <[email protected]>
Acked-by: Marc Zyngier <[email protected]>
Cc: <[email protected]> # v4.6+
Signed-off-by: Christoffer Dall <[email protected]>

Author: murzinv

arch/arm64/kvm/hyp/entry.S

@@ -96,6 +96,8 @@ ENTRY(__guest_exit)
 
 	add	x1, x1, #VCPU_CONTEXT
 
+	ALTERNATIVE(nop, SET_PSTATE_PAN(1), ARM64_HAS_PAN, CONFIG_ARM64_PAN)
+
 	// Store the guest regs x2 and x3
 	stp	x2, x3,   [x1, #CPU_XREG_OFFSET(2)]