On 04.10.21 12:54, Roman Skakun wrote:
Hi Roman
From: Roman Skakun <[email protected]>
Xen is not exposing any IOMMU properties to Dom0.
So Dom0 assumes that all it's devices are not protected by IOMMU.
To make Dom0 aware of IOMMU-protected devices, we need to mark
them somehow. With this approach Dom0 Linux kernel will be able
to selectively disable swiotlb-xen fops for them which will remove
unnecessary buffer bounces.
This patch adds mechanism to describe IOMMU-protected devices by
adding `xen,behind-iommu` property to relevant device nodes in
Dom0 device tree.
I think that new property should be documented probably at
docs/misc/arm/device-tree/...
Signed-off-by: Roman Skakun <[email protected]>
---
xen/arch/arm/domain_build.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 69fff7fc29..99e2c42b6c 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -580,6 +580,13 @@ static int __init write_properties(struct domain *d,
struct kernel_info *kinfo,
return res;
}
+ if ( iommu_node && is_iommu_enabled(d) && dt_device_is_protected(node) )
+ {
+ res = fdt_property(kinfo->fdt, "xen,behind-iommu", NULL, 0);
+ if ( res )
+ return res;
+ }
+
/*
* Override the property "status" to disable the device when it's
* marked for passthrough.
--
Regards,
Oleksandr Tyshchenko
