lkml.org 
[lkml]   [2024]   [Mar]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH] soc: qcom: cmd-db: map shared memory as WT, not WB
From


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@epam.com>
> ---
> 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

\
 
 \ /
  Last update: 2024-05-27 16:13    [W:0.133 / U:0.236 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site