Hi Stefano,
On 26/06/2019 20:02, Stefano Stabellini wrote:
On Mon, 10 Jun 2019, Julien Grall wrote:
At the moment, the fixmap table is only hooked when earlyprintk is used.
This is fine today because in C land, the fixmap is not used by anyone
until the the boot CPU is switching to the runtime page-tables.
In the future, the boot CPU will not switch between page-tables to avoid
TLB conflict. This means the fixmap table will need to be hooked before
any use. For simplicity, setup_fixmap() will now do that job.
Lastly, document the behavior and the main registers usage within the
function.
Signed-off-by: Julien Grall <julien.gr...@arm.com>
---
xen/arch/arm/arm64/head.S | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
index 96e85f8834..4f7fa6769f 100644
--- a/xen/arch/arm/arm64/head.S
+++ b/xen/arch/arm/arm64/head.S
@@ -700,8 +700,17 @@ id_map_removed:
ret
ENDPROC(remove_id_map)
+/*
+ * Map the UART in the fixmap (when earlyprintk is used) and hook the
+ * fixmap table in the page tables.
+ *
+ * The fixmap cannot be mapped in create_page_tables because it may
+ * clash with the ID map.
+ *
+ * Clobbers x0 - x1
I missed this in the last email: it should be x0 - x4?
x0 is not used in the setup_fixmap. So it should be x1 - x4.
Cheers,
--
Julien Grall
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