Re: [MINI-OS PATCH 06/19] mm: don't add module pages to free memory

[Jürgen Groß <jgross@xxxxxxxx>]

On 08.07.25 23:14, Jason Andryuk wrote:
> On 2025-07-02 04:12, Juergen Gross wrote:
> > When initializing the memory allocator, don't add memory pages of
> > modules and the initial boot info structure to the free memory.
> >
> > This is relevant only when running in PVH mode, as in PV mode only
> > memory above the initial page tables is added to free memory, and the
> > module and start_info pages are below the page tables.
> >
> > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> >
> > +/* Reserved memory ranges not added to free memory. */
> > +#define MAX_RSV_RANGES  1
> > +static struct {
> > +    unsigned long start;
> > +    unsigned long size;
> > +} reserved_range[MAX_RSV_RANGES];
> > +
> > +void check_memory_range(unsigned long *from, unsigned long *to)
> > +{
> > +    unsigned int m;
> > +    struct hvm_modlist_entry *mod;
> > +
> > +    for ( m = 0; m < MAX_RSV_RANGES && reserved_range[m].size; m++ )
> > +        check_memory_range_conflict(from, to, reserved_range[m].start,
> > +                                    reserved_range[m].size);
> reserved_range[] isn't updated, so this is dead code.  I guess that is fine for 
> now.
I thought so, yes. It felt more natural to add it in this patch.

> > +
> > +    mod = (struct hvm_modlist_entry *)(unsigned long)
> > +          hvm_start_info_ptr->modlist_paddr;
> > +    for ( m = 0; m < hvm_start_info_ptr->nr_modules; m++ )
> > +        check_memory_range_conflict(from, to, mod[m].paddr, mod[m].size);
> > +}
> > +
> >   static const struct {
> > @@ -888,6 +964,10 @@ void arch_init_mm(unsigned long* start_pfn_p, unsigned 
> > long* max_pfn_p)
> >       if ( max_pfn >= MAX_MEM_SIZE / PAGE_SIZE )
> >           max_pfn = MAX_MEM_SIZE / PAGE_SIZE - 1;
> > +#ifndef CONFIG_PARAVIRT
> > +    pvh_reserve_start_info(&start_pfn);
> > +#endif
> Maybe this ifdef can be removed and arch_mm_preinit() can call 
> pvh_reserve_start_info() and update first_free_pfn (which is assigned to 
> start_pfn)?
Yes, that should be possible.

Thanks for the idea, I'll modify the patch.


Juergen

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