[PATCH v2] armv8: Fix transfer list passing with KVM

[Ilias Apalodimas]

When loading U-Boot in a low memory address, the adpr instruction
to preserve saved_args[] end up within the memory space of QEMUs
mapped pflashes. As a result the following store pair instructions
lead to a crash since instructions that modify more than one registers
can't trap into KVM.

This problem can be solved with loading U-Boot with -kernel
and defining a different text base address. But when running with
-bios we always start from 0x0. So let's postpone the calculation
of saved_args[] post relocation, where we will have an address that
doesn't collide with the QEMU flashes.

Acked-by: Raymond Mao <raymondmaoca at gmail.com>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
---
Changes since v1:
- Move comments to the appropriate place
- Add missing ifdefs when calculating the bloblist placement

 arch/arm/cpu/armv8/start.S | 9 ++++-----
 arch/arm/lib/crt0_64.S     | 7 +++++++
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/arch/arm/cpu/armv8/start.S b/arch/arm/cpu/armv8/start.S
index 40c342e97e9b..c9ca93bcc904 100644
--- a/arch/arm/cpu/armv8/start.S
+++ b/arch/arm/cpu/armv8/start.S
@@ -386,11 +386,10 @@ ENDPROC(c_runtime_cpu_setup)
 
 WEAK(save_boot_params)
 #if (IS_ENABLED(CONFIG_BLOBLIST))
-	/* Calculate the PC-relative address of saved_args */
-	adrp	x9, saved_args
-	add	x9, x9, :lo12:saved_args
-	stp 	x0, x1, [x9]
-	stp 	x2, x3, [x9, #16]
+	mov     x0, x19
+	mov     x1, x20
+	mov     x2, x21
+	mov     x3, x22
 #endif
 	b	save_boot_params_ret	/* back to my caller */
 ENDPROC(save_boot_params)
diff --git a/arch/arm/lib/crt0_64.S b/arch/arm/lib/crt0_64.S
index 3e7627aa389b..588d89687206 100644
--- a/arch/arm/lib/crt0_64.S
+++ b/arch/arm/lib/crt0_64.S
@@ -132,6 +132,13 @@ ENTRY(_main)
 	b	relocate_code
 
 relocation_return:
+#if (IS_ENABLED(CONFIG_BLOBLIST))
+	/* Calculate the PC-relative address of saved_args */
+	adrp    x9, saved_args
+	add     x9, x9, :lo12:saved_args
+	stp     x19, x20, [x9]
+	stp     x21, x22, [x9, #16]
+#endif
 
 /*
  * Set up final (full) environment
-- 
2.51.0