git: 5a08fbb315e8 - stable/13 - arm64: disable the EL2 MMU before dropping to EL1

The branch stable/13 has been updated by kevans:

URL: https://cgit.FreeBSD.org/src/commit/?id=5a08fbb315e82a08022e205e2c2ea4f4d0857f9e

commit 5a08fbb315e82a08022e205e2c2ea4f4d0857f9e
Author:     Kyle Evans <kevans@FreeBSD.org>
AuthorDate: 2022-05-13 03:03:32 +0000
Commit:     Kyle Evans <kevans@FreeBSD.org>
CommitDate: 2022-09-18 06:26:39 +0000

    arm64: disable the EL2 MMU before dropping to EL1
    
    An earlier stage may have set HCR_EL2.E2H, the clearing of which may
    break address translation.  We don't need the EL2 MMU at this point, so
    we can avoid re-enabling it for now and just drop to EL1 as usual.
    
    Suggested by:   andrew
    Reviewed by:    andrew
    
    (cherry picked from commit 51adf913e8815bdc928cb72dd378c596b8b15336)
---
 sys/arm64/arm64/locore.S | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/sys/arm64/arm64/locore.S b/sys/arm64/arm64/locore.S
index 9aeb83008a15..94c8f8b87403 100644
--- a/sys/arm64/arm64/locore.S
+++ b/sys/arm64/arm64/locore.S
@@ -237,6 +237,16 @@ LENTRY(drop_to_el1)
 	b.eq	1f
 	ret
 1:
+	/*
+	 * Disable the MMU. If the HCR_EL2.E2H field is set we will clear it
+	 * which may break address translation.
+	 */
+	dsb	sy
+	mrs	x2, sctlr_el2
+	bic	x2, x2, SCTLR_M
+	msr	sctlr_el2, x2
+	isb
+
 	/* Configure the Hypervisor */
 	mov	x2, #(HCR_RW)
 	msr	hcr_el2, x2