Re: [PATCH 06/15] x86/hyperlaunch: introduce the domain builder

[Jan Beulich <jbeulich@xxxxxxxx>]

On 23.11.2024 19:20, Daniel P. Smith wrote:
> Introduce the domain builder which is capable of consuming a device tree as 
> the
> first boot module. If it finds a device tree as the first boot module, it will
> set its type to BOOTMOD_FDT. This change only detects the boot module and
> continues to boot with slight change to the boot convention that the dom0
> kernel is no longer first boot module but is the second.
> 
> No functional change intended.
> 
> Signed-off-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
> ---
>  xen/arch/x86/Makefile                    |  2 +
>  xen/arch/x86/domain_builder/Makefile     |  3 ++
>  xen/arch/x86/domain_builder/core.c       | 55 ++++++++++++++++++++++++
>  xen/arch/x86/domain_builder/fdt.c        | 38 ++++++++++++++++
>  xen/arch/x86/domain_builder/fdt.h        | 21 +++++++++
>  xen/arch/x86/include/asm/bootinfo.h      |  3 ++
>  xen/arch/x86/include/asm/domainbuilder.h |  8 ++++
>  xen/arch/x86/setup.c                     | 18 +++++---
>  8 files changed, 142 insertions(+), 6 deletions(-)
>  create mode 100644 xen/arch/x86/domain_builder/Makefile
>  create mode 100644 xen/arch/x86/domain_builder/core.c
>  create mode 100644 xen/arch/x86/domain_builder/fdt.c
>  create mode 100644 xen/arch/x86/domain_builder/fdt.h

As I'm sure I indicated before: Dashes instead of underscores please in new
files' names.

>  create mode 100644 xen/arch/x86/include/asm/domainbuilder.h

Why is there no separator in this file's name?

Similar question as on an earlier patch: Why is all of this x86-specific, when
a goal was generalization?

> --- /dev/null
> +++ b/xen/arch/x86/domain_builder/core.c
> @@ -0,0 +1,55 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2024, Apertus Solutions, LLC
> + */
> +#include <xen/err.h>
> +#include <xen/init.h>
> +#include <xen/kconfig.h>
> +#include <xen/lib.h>
> +
> +#include <asm/bootinfo.h>
> +
> +#include "fdt.h"
> +
> +void __init builder_init(struct boot_info *bi)
> +{
> +    if ( IS_ENABLED(CONFIG_DOMAIN_BUILDER) )
> +    {
> +        int ret;
> +
> +        switch ( ret = has_hyperlaunch_fdt(bi) )
> +        {
> +        case 0:
> +            printk("Hyperlaunch device tree detected\n");
> +            bi->hyperlaunch_enabled = true;
> +            bi->mods[0].type = BOOTMOD_FDT;
> +            break;
> +        case -EINVAL:
> +            printk("Hyperlaunch device tree was not detected\n");
> +            bi->hyperlaunch_enabled = false;
> +            break;
> +        case -ENOENT:
> +            fallthrough;

No need for this.

> +        case -ENODATA:
> +            printk("Device tree found, but not hyperlaunch (%d)\n", ret);
> +            bi->hyperlaunch_enabled = false;
> +            bi->mods[0].type = BOOTMOD_FDT;
> +            break;
> +        default:
> +            printk("Unknown error (%d) occured checking for hyperlaunch 
> device tree\n",
> +                   ret);
> +            bi->hyperlaunch_enabled = false;
> +        }

Nit: Misra demands "break" at the end of default as well.

Blank lines between non-fallthrough blocks would also be nice.

> +

Nit: Excess blank line.

> --- /dev/null
> +++ b/xen/arch/x86/domain_builder/fdt.c
> @@ -0,0 +1,38 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2024, Apertus Solutions, LLC
> + */
> +#include <xen/err.h>
> +#include <xen/init.h>
> +#include <xen/lib.h>
> +#include <xen/libfdt/libfdt.h>
> +#include <xen/rangeset.h> /* required for asm/setup.h */
> +
> +#include <asm/bootinfo.h>
> +#include <asm/page.h>
> +#include <asm/setup.h>
> +
> +#include "fdt.h"
> +
> +int __init has_hyperlaunch_fdt(struct boot_info *bi)
> +{
> +    int ret = 0;
> +    void *fdt = bootstrap_map_bm(&bi->mods[HYPERLAUNCH_MODULE_IDX]);

const void *?

> @@ -1277,9 +1278,12 @@ void asmlinkage __init noreturn __start_xen(void)
>                 bi->nr_modules);
>      }
>  
> -    /* Dom0 kernel is always first */
> -    bi->mods[0].type = BOOTMOD_KERNEL;
> -    bi->domains[0].kernel = &bi->mods[0];
> +    builder_init(bi);
> +
> +    /* Find first unknown boot module to use as Dom0 kernel */
> +    i = first_boot_module_index(bi, BOOTMOD_UNKNOWN);
> +    bi->mods[i].type = BOOTMOD_KERNEL;
> +    bi->domains[0].kernel = &bi->mods[i];

Better latch the result here into a separate local variable, for use ...

> @@ -1466,8 +1470,9 @@ void asmlinkage __init noreturn __start_xen(void)
>          xen->size  = __2M_rwdata_end - _stext;
>      }
>  
> -    bi->mods[0].headroom =
> -        bzimage_headroom(bootstrap_map_bm(&bi->mods[0]), bi->mods[0].size);
> +    i = first_boot_module_index(bi, BOOTMOD_KERNEL);
> +    bi->mods[i].headroom =
> +        bzimage_headroom(bootstrap_map_bm(&bi->mods[i]), bi->mods[i].size);
>      bootstrap_unmap();
>  
>  #ifndef highmem_start
> @@ -1591,7 +1596,8 @@ void asmlinkage __init noreturn __start_xen(void)
>  #endif
>      }
>  
> -    if ( bi->mods[0].headroom && !bi->mods[0].relocated )
> +    i = first_boot_module_index(bi, BOOTMOD_KERNEL);
> +    if ( bi->mods[i].headroom && !bi->mods[0].relocated )
>          panic("Not enough memory to relocate the dom0 kernel image\n");
>      for ( i = 0; i < bi->nr_modules; ++i )
>      {

... in these two places?

Jan