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. 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. -- 2.27.0
