ARM: virt: simplify __hyp_stub_install epilog

__hyp_stub_install duplicates quite a bit of safe_svcmode_maskall
by forcing the CPU back to SVC. This is unnecessary, as
safe_svcmode_maskall is called just after.

Furthermore, the way we build SPSR_hyp is buggy as we fail to mask
the interrupts, leading to interesting behaviours on TC2 + UEFI.

The fix is to simply remove this code and rely on safe_svcmode_maskall
to do the right thing.

Cc: <stable@vger.kernel.org>
Reviewed-by: NDave Martin <dave.martin@linaro.org>
Reported-by: NHarry Liebel <harry.liebel@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

arch/arm/kernel/hyp-stub.S

@@ -120,7 +120,8 @@ ENTRY(__hyp_stub_install_secondary)
  * Eventually, CPU-specific code might be needed -- assume not for now
  *
  * This code relies on the "eret" instruction to synchronize the
- * various coprocessor accesses.
+ * various coprocessor accesses. This is done when we switch to SVC
+ * (see safe_svcmode_maskall).
  */
 	@ Now install the hypervisor stub:
 	adr	r7, __hyp_stub_vectors
@@ -155,14 +156,7 @@ THUMB(	orr	r7, #(1 << 30)	)	@ HSCTLR.TE
 1:
 #endif
 
-	bic	r7, r4, #MODE_MASK
-	orr	r7, r7, #SVC_MODE
-THUMB(	orr	r7, r7, #PSR_T_BIT	)
-	msr	spsr_cxsf, r7		@ This is SPSR_hyp.
-
-	__MSR_ELR_HYP(14)		@ msr elr_hyp, lr
-	__ERET				@ return, switching to SVC mode
-					@ The boot CPU mode is left in r4.
+	bx	lr			@ The boot CPU mode is left in r4.
 ENDPROC(__hyp_stub_install_secondary)
 
 __hyp_stub_do_trap: