[RFC PATCH 15/31] efi_memory: add an event handler to update memory map

[Sughosh Ganu]

On Mon, 10 Jun 2024 at 17:40, Ilias Apalodimas
<ilias.apalodimas at linaro.org> wrote:
>
> On Fri, 7 Jun 2024 at 21:54, Sughosh Ganu <sughosh.ganu at linaro.org> wrote:
> >
> > There are events that would be used to notify other interested modules
> > of any changes in available and occupied memory. This would happen
> > when a module allocates or reserves memory, or frees up memory. These
> > changes in memory map should be notified to other interested modules
> > so that the allocated memory does not get overwritten. Add an event
> > handler in the EFI memory module to update the EFI memory map
> > accordingly when such changes happen. As a consequence, any subsequent
> > memory request would honour the updated memory map and only available
> > memory would be allocated from.
>
> So the question here, is why do we need a notifier chain overall?
> Can't we change the EFI subsystem and allocate memory with lmb now?
> And any special functions we have in EFI (e.g allocate aligned memory)
> can migrate to lmb()

Like we discussed offline, that was my initial attempt -- to use the
LMB allocation API's from inside the EFI allocate pages module. But I
was facing a lot of corner case issues, primarily in keeping the two
memory maps the same. Which is why I moved to the current
implementation of notifying other modules, and that too only for the
addresses in the RAM region.

-sughosh

>
> Cheers
> /Ilias
> >
> > Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
> > ---
> >  lib/efi_loader/efi_memory.c | 70 ++++++++++++++++++++++++++++++-------
> >  1 file changed, 58 insertions(+), 12 deletions(-)
> >
> > diff --git a/lib/efi_loader/efi_memory.c b/lib/efi_loader/efi_memory.c
> > index 435e580fb3..93244161b0 100644
> > --- a/lib/efi_loader/efi_memory.c
> > +++ b/lib/efi_loader/efi_memory.c
> > @@ -73,6 +73,10 @@ struct efi_pool_allocation {
> >  #if CONFIG_IS_ENABLED(MEM_MAP_UPDATE_NOTIFY)
> >  extern bool is_addr_in_ram(uintptr_t addr);
> >
> > +static efi_status_t __efi_add_memory_map_pg(u64 start, u64 pages,
> > +                                           int memory_type,
> > +                                           bool overlap_only_ram);
> > +
> >  static void efi_map_update_notify(u64 addr, u64 size, u8 op)
> >  {
> >         struct event_efi_mem_map_update efi_map = {0};
> > @@ -84,6 +88,34 @@ static void efi_map_update_notify(u64 addr, u64 size, u8 op)
> >         if (is_addr_in_ram((uintptr_t)addr))
> >                 event_notify(EVT_EFI_MEM_MAP_UPDATE, &efi_map, sizeof(efi_map));
> >  }
> > +
> > +static int lmb_mem_map_update_sync(void *ctx, struct event *event)
> > +{
> > +       u8 op;
> > +       u64 addr;
> > +       u64 pages;
> > +       efi_status_t status;
> > +       struct event_lmb_map_update *lmb_map = &event->data.lmb_map;
> > +
> > +       addr = (uintptr_t)map_sysmem(lmb_map->base, 0);
> > +       pages = efi_size_in_pages(lmb_map->size + (addr & EFI_PAGE_MASK));
> > +       op = lmb_map->op;
> > +       addr &= ~EFI_PAGE_MASK;
> > +
> > +       if (op != MAP_OP_RESERVE && op != MAP_OP_FREE) {
> > +               log_debug("Invalid map update op received (%d)\n", op);
> > +               return -1;
> > +       }
> > +
> > +       status = __efi_add_memory_map_pg(addr, pages,
> > +                                        op == MAP_OP_FREE ?
> > +                                        EFI_CONVENTIONAL_MEMORY :
> > +                                        EFI_BOOT_SERVICES_DATA,
> > +                                        true);
> > +
> > +       return status == EFI_SUCCESS ? 0 : -1;
> > +}
> > +EVENT_SPY_FULL(EVT_LMB_MAP_UPDATE, lmb_mem_map_update_sync);
> >  #endif /* MEM_MAP_UPDATE_NOTIFY */
> >
> >  /**
> > @@ -275,18 +307,9 @@ static s64 efi_mem_carve_out(struct efi_mem_list *map,
> >         return EFI_CARVE_LOOP_AGAIN;
> >  }
> >
> > -/**
> > - * efi_add_memory_map_pg() - add pages to the memory map
> > - *
> > - * @start:             start address, must be a multiple of EFI_PAGE_SIZE
> > - * @pages:             number of pages to add
> > - * @memory_type:       type of memory added
> > - * @overlap_only_ram:  region may only overlap RAM
> > - * Return:             status code
> > - */
> > -static efi_status_t efi_add_memory_map_pg(u64 start, u64 pages,
> > -                                         int memory_type,
> > -                                         bool overlap_only_ram)
> > +static efi_status_t __efi_add_memory_map_pg(u64 start, u64 pages,
> > +                                           int memory_type,
> > +                                           bool overlap_only_ram)
> >  {
> >         struct list_head *lhandle;
> >         struct efi_mem_list *newlist;
> > @@ -395,6 +418,29 @@ static efi_status_t efi_add_memory_map_pg(u64 start, u64 pages,
> >                 }
> >         }
> >
> > +       return EFI_SUCCESS;
> > +}
> > +
> > +/**
> > + * efi_add_memory_map_pg() - add pages to the memory map
> > + *
> > + * @start:             start address, must be a multiple of EFI_PAGE_SIZE
> > + * @pages:             number of pages to add
> > + * @memory_type:       type of memory added
> > + * @overlap_only_ram:  region may only overlap RAM
> > + * Return:             status code
> > + */
> > +static efi_status_t efi_add_memory_map_pg(u64 start, u64 pages,
> > +                                         int memory_type,
> > +                                         bool overlap_only_ram)
> > +{
> > +       efi_status_t status;
> > +
> > +       status = __efi_add_memory_map_pg(start, pages, memory_type,
> > +                                        overlap_only_ram);
> > +       if (status != EFI_SUCCESS)
> > +               return status;
> > +
> >         if (CONFIG_IS_ENABLED(MEM_MAP_UPDATE_NOTIFY))
> >                 efi_map_update_notify(start, pages << EFI_PAGE_SHIFT,
> >                                       memory_type == EFI_CONVENTIONAL_MEMORY ?
> > --
> > 2.34.1
> >