Messages in this thread | | | Date | Thu, 28 Mar 2024 17:31:04 +0530 | Subject | Re: [PATCH] soc: qcom: cmd-db: map shared memory as WT, not WB | From | "Maulik Shah (mkshah)" <> |
| |
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
| |