On 3/28/2024 1:39 AM, Volodymyr Babchuk wrote:
It appears that hardware does not like cacheable accesses to this
region. Trying to access this shared memory region as Normal Memory
leads to secure interrupt which causes an endless loop somewhere in
Trust Zone.
Linux does not write into cmd-db region. This region is write protected
by XPU. Making this region uncached magically solves the XPU write fault
issue.
Can you please include above details?
The only reason it is working right now is because Qualcomm Hypervisor
maps the same region as Non-Cacheable memory in Stage 2 translation
tables. The issue manifests if we want to use another hypervisor (like
Xen or KVM), which does not know anything about those specific
mappings. This patch fixes the issue by mapping the shared memory as
Write-Through. This removes dependency on correct mappings in Stage 2
tables.
Using MEMREMAP_WC also resolves for qcm6490, see below comment.
I tested this on SA8155P with Xen.
Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
---
drivers/soc/qcom/cmd-db.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/soc/qcom/cmd-db.c b/drivers/soc/qcom/cmd-db.c
index a5fd68411bed5..dd5ababdb476c 100644
--- a/drivers/soc/qcom/cmd-db.c
+++ b/drivers/soc/qcom/cmd-db.c
@@ -324,7 +324,7 @@ static int cmd_db_dev_probe(struct platform_device *pdev)
return -EINVAL;
}
- cmd_db_header = memremap(rmem->base, rmem->size, MEMREMAP_WB);
+ cmd_db_header = memremap(rmem->base, rmem->size, MEMREMAP_WT);
In downstream, we have below which resolved similar issue on qcm6490.
cmd_db_header = memremap(rmem->base, rmem->size, MEMREMAP_WC);
Downstream SA8155P also have MEMREMAP_WC. Can you please give it a try
on your device?
Thanks,
Maulik
