[PATCH v24 5/9] arm64: kdump: add kdump support

[Dave Young]

On 08/24/16 at 11:25am, James Morse wrote:
> Hi Dave,
> 
> On 24/08/16 09:04, Dave Young wrote:
> > Looking the arm-init.c, I suspect it missed the some efi ranges as
> > reserved ranges like runtime code and runtime data etc. But I might be
> > wrong.
> 
> This had me confused for too... I think I get it, my understanding is:
> 
James, thanks for your clarification. 
> 
> > static __init int is_reserve_region(efi_memory_desc_t *md)
> > {
> >         switch (md->type) {
> >         case EFI_LOADER_CODE:
> >         case EFI_LOADER_DATA:
> >         case EFI_BOOT_SERVICES_CODE:
> >         case EFI_BOOT_SERVICES_DATA:
> >         case EFI_CONVENTIONAL_MEMORY:
> >         case EFI_PERSISTENT_MEMORY:
> >                 return 0;
> 
> return false - this is the list of region-types to never reserve, regardless of
> memory attributes.
> 
> 
> >         default:
> >                 break;
> >         }
> >         return is_normal_ram(md);
> 
> If its not in the 'never reserve' list above, then we check if the region is
> 'normal' ram. If it is then it will end up in memblock.memory so we return true,
> causing it to be marked nomap too.
> 
> reserve_regions() in that same file calls is_normal_ram() directly before adding
> all regions with the WB attribute to memblock.memory via
> early_init_dt_add_memory_arch().
> 
> A runtime region with the WB attribute will be caught by is_reserve_region(),
> and is_normal_ram(), so it ends up in memblock.memory and memblock.nomap.

Hmm, It is not straitforward like the do_add_efi_memmap. I got it.

BTW, I believe there is same problem in arm as well as arm64, it also
need mark the runtime ranges as "reserved" /proc/iomem. 

> 
> 
> > }
> > 
> > Let's see the x86 do_add_efi_mem_map, the default case set all other
> > types as reserved. Shouldn't this be same in all arches though there's
> > no e820 in arm(64)?
> 
> > static void __init do_add_efi_memmap(void)
> > {
> > 
> > [snip]
> >                 switch (md->type) {
> >                 case EFI_LOADER_CODE:
> >                 case EFI_LOADER_DATA:
> >                 case EFI_BOOT_SERVICES_CODE:
> >                 case EFI_BOOT_SERVICES_DATA:
> >                 case EFI_CONVENTIONAL_MEMORY:
> >                         if (md->attribute & EFI_MEMORY_WB)
> >                                 e820_type = E820_RAM;
> 
> In this case reserve_regions() will add the memory to memblock.memory because it
> has the WB attribute, and not reserve it.
> 
> 
> >                         else
> >                                 e820_type = E820_RESERVED;
> 
> Without the WB attribute, these regions are in neither memblock.memory nor
> memblock.nomap.
> 
> 
> >                         break;
> > [snip]
> >                 default:
> >                         /*
> >                          * EFI_RESERVED_TYPE EFI_RUNTIME_SERVICES_CODE
> >                          * EFI_RUNTIME_SERVICES_DATA
> >                          * EFI_MEMORY_MAPPED_IO
> >                          * EFI_MEMORY_MAPPED_IO_PORT_SPACE EFI_PAL_CODE
> >                          */
> >                         e820_type = E820_RESERVED;
> >                         break;
> 
> If any other regions has the WB attribute, it will be added to memblock.memory
> and memblock.nomap. If it doesn't, it will appear in neither.
> 
> 
> >                 }
> > [snip]
> > }
> 
> Does this help at all?
> 

Yes, thanks a lot!
Dave

> 
> Thanks,
> 
> James