Re: [Xen-devel] [PATCH v3 2/6] xen/arm: copy dtb fragment to guest dtb

[Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>]

Hi Stefano,

Stefano Stabellini writes:

> Read the dtb fragment corresponding to a passthrough device from memory
> at the location referred to by the "multiboot,dtb" compatible node.
>
> Copy the fragment to the guest dtb.
>
> Add a dtb_bootmodule field to struct kernel_info to find the dtb
> fragment for a guest.
>
> Some of the code below is taken from tools/libxl/libxl_arm.c. Note that
> it is OK to take LGPL 2.1 code and including it into a GPLv2 code base.
> The result is GPLv2 code.
>
> Signed-off-by: Stefano Stabellini <stefanos@xxxxxxxxxx>
>
> ----
> Changes in v3:
> - switch to using device_tree_for_each_node for the copy
>
> Changes in v2:
> - add a note about the code coming from libxl in the commit message
> - copy /aliases
> - code style
> ---
>  xen/arch/arm/domain_build.c  | 103 +++++++++++++++++++++++++++++++++++
>  xen/include/asm-arm/kernel.h |   2 +-
>  2 files changed, 104 insertions(+), 1 deletion(-)
>
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index 00ddb3b05d..70bcdc449d 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -14,6 +14,7 @@
>  #include <xen/guest_access.h>
>  #include <xen/iocap.h>
>  #include <xen/acpi.h>
> +#include <xen/vmap.h>
>  #include <xen/warning.h>
>  #include <acpi/actables.h>
>  #include <asm/device.h>
> @@ -1706,6 +1707,102 @@ static int __init make_vpl011_uart_node(const struct 
> domain *d, void *fdt)
>  }
>  #endif
>
> +static int __init handle_properties(struct domain *d, void *fdt, const void 
> *pfdt, int nodeoff,
> +                                    u32 address_cells, u32 size_cells)
nitpicking: "handle_properties" is somewhat non-descriptive in context
of this file. From this name it is hard to tell that this function
copies properties of FDT node.

> +{
> +    int propoff, nameoff, r;
> +    const struct fdt_property *prop;
> +
> +    for ( propoff = fdt_first_property_offset(pfdt, nodeoff);
> +          propoff >= 0;
> +          propoff = fdt_next_property_offset(pfdt, propoff) )
> +    {
> +
Do you really need this empty line?

> +        if ( !(prop = fdt_get_property_by_offset(pfdt, propoff, NULL)) )
> +            return -FDT_ERR_INTERNAL;
> +
> +        nameoff = fdt32_to_cpu(prop->nameoff);
> +        r = fdt_property(fdt, fdt_string(pfdt, nameoff),
> +                         prop->data, fdt32_to_cpu(prop->len));
> +        if ( r )
> +            return r;
> +    }
> +
> +    /* FDT_ERR_NOTFOUND => There is no more properties for this node */
> +    return ( propoff != -FDT_ERR_NOTFOUND ) ? propoff : 0;
> +}
> +
> +static int __init scan_pt_node(const void *pfdt,
> +                               int nodeoff, const char *name, int depth,
> +                               u32 address_cells, u32 size_cells,
> +                               void *data)
> +{
> +    int rc;
> +    int i, num;
> +    struct kernel_info *kinfo = data;
> +    void *fdt = kinfo->fdt;
> +    int depth_next = depth;
> +    int node_next;
> +
> +    /* no need to parse initial node */
> +    if ( !depth )
> +        return 0;
> +
> +    rc = fdt_begin_node(fdt, fdt_get_name(pfdt, nodeoff, NULL));
> +    if ( rc )
> +        return rc;
> +
> +    rc = handle_properties(kinfo->d, fdt, pfdt, nodeoff,
> +                           address_cells, size_cells);
> +    if ( rc )
> +        return rc;
> +
> +    node_next = fdt_next_node(pfdt, nodeoff, &depth_next);
> +
> +    /*
> +     * If the next node is a sibling, then we need to call
> +     * fdt_end_node once. If the next node is one level up, we need to
> +     * call it twice: once for us and the second time for our parent.
> +     * Both these two conditions are expressed together by depth -
> +     * depth_next + 1.
> +     *
> +     * If we reached the end of the device tree fragment, then it is
> +     * easy: we need to call fdt_end_node once for every level of depth
> +     * to close all open nodes.
> +     */
> +    if ( depth_next < 0 )
> +        num = depth;
> +    else
> +        num = depth - depth_next + 1;
> +
> +    for ( i = 0; i < num; i++ )
> +    {
> +        rc = fdt_end_node(fdt);
> +        if ( rc )
> +            return rc;
> +    }
> +
> +    return 0;
> +}
> +
> +static int __init domain_handle_dtb_bootmodule(struct domain *d,
> +                                               struct kernel_info *kinfo)
> +{
> +    void *pfdt;
> +    int res;
> +
> +    pfdt = ioremap_cache(kinfo->dtb_bootmodule->start,
> +            kinfo->dtb_bootmodule->size);
> +    if ( pfdt == NULL )
> +        return -EFAULT;
> +
> +    res = device_tree_for_each_node(pfdt, scan_pt_node, kinfo);
> +
> +    iounmap(pfdt);
> +
> +    return res;
> +}
> +
>  /*
>   * The max size for DT is 2MB. However, the generated DT is small, 4KB
>   * are enough for now, but we might have to increase it in the future.
> @@ -1777,6 +1874,12 @@ static int __init prepare_dtb_domU(struct domain *d, 
> struct kernel_info *kinfo)
>              goto err;
>      }
>
> +    if ( kinfo->dtb_bootmodule ) {
> +        ret = domain_handle_dtb_bootmodule(d, kinfo);
> +        if ( ret )
> +            return ret;
> +    }
> +
>      ret = fdt_end_node(kinfo->fdt);
>      if ( ret < 0 )
>          goto err;
> diff --git a/xen/include/asm-arm/kernel.h b/xen/include/asm-arm/kernel.h
> index 33f3e72b11..720dec4071 100644
> --- a/xen/include/asm-arm/kernel.h
> +++ b/xen/include/asm-arm/kernel.h
> @@ -28,7 +28,7 @@ struct kernel_info {
>      paddr_t gnttab_size;
>
>      /* boot blob load addresses */
> -    const struct bootmodule *kernel_bootmodule, *initrd_bootmodule;
> +    const struct bootmodule *kernel_bootmodule, *initrd_bootmodule, 
> *dtb_bootmodule;
>      const char* cmdline;
>      paddr_t dtb_paddr;
>      paddr_t initrd_paddr;


--
Volodymyr Babchuk at EPAM
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel