arm64: Allow sticky E2H when entering EL1

For CPUs that have the unfortunate mis-feature to be stuck in
VHE mode, we perform a funny dance where we completely shortcut
the normal boot process to enable VHE and run the kernel at EL2,
and only then start booting the kernel.

Not only this is pretty ugly, but it means that the EL2 finalisation
occurs before we have processed the sysreg override.

Instead, start executing the kernel as if it was an EL1 guest and
rely on the normal EL2 finalisation to go back to EL2.
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220630160500.1536744-4-maz@kernel.orgSigned-off-by: Will Deacon <will@kernel.org>

arch/arm64/kernel/head.S

@@ -511,6 +511,8 @@ SYM_INNER_LABEL(init_el2, SYM_L_LOCAL)
 	msr	vbar_el2, x0
 	isb
 
+	mov_q	x1, INIT_SCTLR_EL1_MMU_OFF
+
 	/*
 	 * Fruity CPUs seem to have HCR_EL2.E2H set to RES1,
 	 * making it impossible to start in nVHE mode. Is that
@@ -520,35 +522,19 @@ SYM_INNER_LABEL(init_el2, SYM_L_LOCAL)
 	and	x0, x0, #HCR_E2H
 	cbz	x0, 1f
 
-	/* Switching to VHE requires a sane SCTLR_EL1 as a start */
-	mov_q	x0, INIT_SCTLR_EL1_MMU_OFF
-	msr_s	SYS_SCTLR_EL12, x0
-
-	/*
-	 * Force an eret into a helper "function", and let it return
-	 * to our original caller... This makes sure that we have
-	 * initialised the basic PSTATE state.
-	 */
-	mov	x0, #INIT_PSTATE_EL2
-	msr	spsr_el1, x0
-	adr	x0, __cpu_stick_to_vhe
-	msr	elr_el1, x0
-	eret
+	/* Set a sane SCTLR_EL1, the VHE way */
+	msr_s	SYS_SCTLR_EL12, x1
+	mov	x2, #BOOT_CPU_FLAG_E2H
+	b	2f
 
 1:
-	mov_q	x0, INIT_SCTLR_EL1_MMU_OFF
-	msr	sctlr_el1, x0
-
+	msr	sctlr_el1, x1
+	mov	x2, xzr
+2:
 	msr	elr_el2, lr
 	mov	w0, #BOOT_CPU_MODE_EL2
+	orr	x0, x0, x2
 	eret
-
-__cpu_stick_to_vhe:
-	mov	x0, #HVC_FINALISE_EL2
-	hvc	#0
-	mov	x0, #BOOT_CPU_MODE_EL2
-	orr	x0, x0, #BOOT_CPU_FLAG_E2H
-	ret
 SYM_FUNC_END(init_kernel_el)
 
 /*