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

["Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>]

On 12/12/24 06:06, Jan Beulich wrote:
> On 11.12.2024 13:36, Daniel P. Smith wrote:
> > On 12/2/24 05:10, Jan Beulich wrote:
> > > 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?
> > Name was getting a bit long, but can add separator if desired.
> Well, my desire is for the subdir and the header names to match up.
> Personally I think that neater to achieve when both have a dash in the
> middle.
Sure.

> > > > --- /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.
> > I thought MISRA called for explicit fallthrough?
> Only when there are statements between two case labels. Which ...
>
> > > > +        case -ENODATA:
> ... isn't the case here.
Rgr, have already dropped it.

> > > > @@ -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?
> > I don't know if a local variable is need. I assume your suggestion is to
> > drop the first_boot_module_index() call,
> The latter two of the three, yes.
>
> > but thinking about it, not sure
> > why I kept the walk. A direct use of bi->domains[0].kernel could be used
> > without the intermediate variable while removing the call.
> If that's possible, the even better.
Yep, while it did make the lines a little longer, I was able to use the 
boot_domain reference.
v/r,
dps