[RFC PATCH v2 10/18] arm64: head: record the MMU state at primary entry

[Ard Biesheuvel]

Prepare for being able to deal with primary entry with the MMU and
caches enabled, by recording whether or not we entered with the MMU on
in register x22.

While at it, add disable_mmu_workaround macro invocations to
init_kernel_el, as its manipulation of SCTLR_ELx may come down to
disabling of the MMU after subsequent patches.

Signed-off-by: Ard Biesheuvel <ardb at kernel.org>
---
 arch/arm64/kernel/head.S | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index f3b096daf1c5..44e2e39046a9 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -83,9 +83,11 @@
 	 *
 	 *  Register   Scope                      Purpose
 	 *  x21        primary_entry() .. start_kernel()        FDT pointer passed at boot in x0
+	 *  x22        primary_entry() .. start_kernel()        whether we entered with the MMU on
 	 *  x23        __primary_switch() .. relocate_kernel()  physical misalignment/KASLR offset
 	 */
 SYM_CODE_START(primary_entry)
+	bl	record_mmu_state
 	bl	preserve_boot_args
 	bl	init_kernel_el			// w0=cpu_boot_mode
 	bl	set_cpu_boot_mode_flag
@@ -101,6 +103,17 @@ SYM_CODE_START(primary_entry)
 	b	__primary_switch
 SYM_CODE_END(primary_entry)
 
+SYM_CODE_START_LOCAL(record_mmu_state)
+	mrs	x22, CurrentEL
+	cmp	x22, #CurrentEL_EL2
+	mrs	x22, sctlr_el1
+	b.ne	0f
+	mrs	x22, sctlr_el2
+0:	tst	x22, #SCTLR_ELx_M
+	cset	w22, ne
+	ret
+SYM_CODE_END(record_mmu_state)
+
 /*
  * Preserve the arguments passed by the bootloader in x0 .. x3
  */
@@ -485,6 +498,7 @@ SYM_FUNC_START(init_kernel_el)
 
 SYM_INNER_LABEL(init_el1, SYM_L_LOCAL)
 	mov_q	x0, INIT_SCTLR_EL1_MMU_OFF
+	pre_disable_mmu_workaround
 	msr	sctlr_el1, x0
 	isb
 	mov_q	x0, INIT_PSTATE_EL1
@@ -516,6 +530,7 @@ SYM_INNER_LABEL(init_el2, SYM_L_LOCAL)
 
 	/* Switching to VHE requires a sane SCTLR_EL1 as a start */
 	mov_q	x0, INIT_SCTLR_EL1_MMU_OFF
+	pre_disable_mmu_workaround
 	msr_s	SYS_SCTLR_EL12, x0
 
 	/*
@@ -531,6 +546,7 @@ SYM_INNER_LABEL(init_el2, SYM_L_LOCAL)
 
 1:
 	mov_q	x0, INIT_SCTLR_EL1_MMU_OFF
+	pre_disable_mmu_workaround
 	msr	sctlr_el1, x0
 
 	msr	elr_el2, lr
-- 
2.30.2