On Mon, 19 May 2025, Oleksii Moisieiev wrote:
> From: Grygorii Strashko <grygorii_stras...@epam.com>
>
> Add chained handling of assigned DT devices to support access-controller
> functionality through SCI framework, so DT device assign request can be
> passed to FW for processing and enabling VM access to requested device
> (for example, device power management through FW interface like SCMI).
>
> The SCI access-controller DT device processing is chained after IOMMU
> processing and expected to be executed for any DT device regardless of its
> protection by IOMMU (or if IOMMU is disabled).
>
> This allows to pass not only IOMMU protected DT device through
> xl.cfg:"dtdev" property for processing:
>
> dtdev = [
> "/soc/video@e6ef0000", <- IOMMU protected device
> "/soc/i2c@e6508000", <- not IOMMU protected device
> ]
>
> The change is done in two parts:
> 1) update iommu_do_dt_domctl() to check for dt_device_is_protected() and
> not fail if DT device is not protected by IOMMU
> 2) add chained call to sci_do_domctl() in do_domctl()
>
> Signed-off-by: Grygorii Strashko <grygorii_stras...@epam.com>
> Signed-off-by: Oleksii Moisieiev <oleksii_moisie...@epam.com>
> ---
>
>
>
> xen/arch/arm/firmware/sci.c | 37 +++++++++++++++++++++++++
> xen/arch/arm/include/asm/firmware/sci.h | 14 ++++++++++
> xen/common/domctl.c | 19 +++++++++++++
> xen/drivers/passthrough/device_tree.c | 6 ++++
> 4 files changed, 76 insertions(+)
>
> diff --git a/xen/arch/arm/firmware/sci.c b/xen/arch/arm/firmware/sci.c
> index e1522e10e2..8efd541c4f 100644
> --- a/xen/arch/arm/firmware/sci.c
> +++ b/xen/arch/arm/firmware/sci.c
> @@ -126,6 +126,43 @@ int sci_assign_dt_device(struct domain *d, struct
> dt_device_node *dev)
> return 0;
> }
>
> +int sci_do_domctl(struct xen_domctl *domctl, struct domain *d,
> + XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
> +{
> + struct dt_device_node *dev;
> + int ret = 0;
> +
> + switch ( domctl->cmd )
> + {
> + case XEN_DOMCTL_assign_device:
> + ret = -EOPNOTSUPP;
Are you sure -EOPNOTSUPP is the right error code for the 3 checks below?
> + if ( domctl->u.assign_device.dev != XEN_DOMCTL_DEV_DT )
> + break;
this one
> + if ( !cur_mediator )
> + break;
this one
> + if ( !cur_mediator->assign_dt_device )
> + break;
and also this one? It seems more like an -EINVAL as the caller used a
wrong parameter?
> + ret = dt_find_node_by_gpath(domctl->u.assign_device.u.dt.path,
> + domctl->u.assign_device.u.dt.size, &dev);
> + if ( ret )
> + return ret;
> +
> + ret = sci_assign_dt_device(d, dev);
> + if ( ret )
> + break;
> +
> + break;
> + default:
> + /* do not fail here as call is chained with iommu handling */
It looks like this should be an error
> + break;
> + }
> +
> + return ret;
> +}
> +
> static int __init sci_init(void)
> {
> struct dt_device_node *np;
> diff --git a/xen/arch/arm/include/asm/firmware/sci.h
> b/xen/arch/arm/include/asm/firmware/sci.h
> index 71fb54852e..b8d1bc8a62 100644
> --- a/xen/arch/arm/include/asm/firmware/sci.h
> +++ b/xen/arch/arm/include/asm/firmware/sci.h
> @@ -146,6 +146,14 @@ int sci_dt_finalize(struct domain *d, void *fdt);
> * control" functionality.
> */
> int sci_assign_dt_device(struct domain *d, struct dt_device_node *dev);
> +
> +/*
> + * SCI domctl handler
> + *
> + * Only XEN_DOMCTL_assign_device is handled for now.
> + */
> +int sci_do_domctl(struct xen_domctl *domctl, struct domain *d,
> + XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl);
> #else
>
> static inline bool sci_domain_is_enabled(struct domain *d)
> @@ -195,6 +203,12 @@ static inline int sci_assign_dt_device(struct domain *d,
> return 0;
> }
>
> +static inline int sci_do_domctl(struct xen_domctl *domctl, struct domain *d,
> + XEN_GUEST_HANDLE_PARAM(xen_domctl_t)
> u_domctl)
> +{
> + return 0;
> +}
> +
> #endif /* CONFIG_ARM_SCI */
>
> #endif /* __ASM_ARM_SCI_H */
> diff --git a/xen/common/domctl.c b/xen/common/domctl.c
> index 05abb581a0..a74ee92067 100644
> --- a/xen/common/domctl.c
> +++ b/xen/common/domctl.c
> @@ -27,6 +27,7 @@
> #include <xen/vm_event.h>
> #include <xen/monitor.h>
> #include <asm/current.h>
> +#include <asm/firmware/sci.h>
> #include <asm/irq.h>
> #include <asm/page.h>
> #include <asm/p2m.h>
> @@ -851,6 +852,24 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t)
> u_domctl)
> case XEN_DOMCTL_deassign_device:
> case XEN_DOMCTL_get_device_group:
> ret = iommu_do_domctl(op, d, u_domctl);
> +
> + if ( !ret || ret == -EOPNOTSUPP )
It is better to invert the check:
if ( ret < 0 && ret != -EOPNOTSUPP )
return ret;
> + {
> + int ret1;
> + /*
> + * Add chained handling of assigned DT devices to support
> + * access-controller functionality through SCI framework, so
> + * DT device assign request can be passed to FW for processing
> and
> + * enabling VM access to requested device.
> + * The access-controller DT device processing is chained after
> IOMMU
> + * processing and expected to be executed for any DT device
> + * regardless if DT device is protected by IOMMU or not (or IOMMU
> + * is disabled).
> + */
> + ret1 = sci_do_domctl(op, d, u_domctl);
> + if ( ret1 != -EOPNOTSUPP )
> + ret = ret1;
> + }
> break;
>
> case XEN_DOMCTL_get_paging_mempool_size:
> diff --git a/xen/drivers/passthrough/device_tree.c
> b/xen/drivers/passthrough/device_tree.c
> index 075fb25a37..2624767e51 100644
> --- a/xen/drivers/passthrough/device_tree.c
> +++ b/xen/drivers/passthrough/device_tree.c
> @@ -318,6 +318,12 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, struct
> domain *d,
> break;
> }
>
> + if ( !dt_device_is_protected(dev) )
> + {
> + ret = 0;
> + break;
> + }
I am concerned about this: previously we would call
iommu_assign_dt_device and the same check at the beginning of
iommu_assign_dt_device would return -EINVAL. Now it is a success.
I am not sure this is appropriate. I wonder if instead we should:
- remove this chunk from the patch
- change the return error for !dt_device_is_protected at the top of
iommu_assign_dt_device from -EINVAL to -EOPNOTSUPP
- this would fall into the same ret != -EOPNOTSUPP check after
iommu_do_domctl
> ret = iommu_assign_dt_device(d, dev);
>
> if ( ret )
> --
> 2.34.1
>
