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



On Fri, 9 Aug 2019, Volodymyr Babchuk wrote:
> 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.

I'll rename it to handle_prop_pfdt: the important message to convey is
that it is a function to handle the properties of the partial device
tree.


> > +{
> > +    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?

I'll remove it


> > +        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

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