On Wed, Aug 24, 2016 at 05:24:16PM +0200, Ard Biesheuvel wrote: > Currently, memory regions are only recorded in the memblock memory table > if they have the EFI_MEMORY_WB memory type attribute set. In case the > region is of a reserved type, it is also marked as MEMBLOCK_NOMAP, which > will leave it out of the linear mapping. > > However, memory regions may legally have the EFI_MEMORY_WT or EFI_MEMORY_WC > attributes set, and the EFI_MEMORY_WB cleared, in which case the region in > question is obviously backed by normal memory, but is not recorded in the > memblock memory table at all. Since it would be useful to be able to > identify any UEFI reported memory region using memblock_is_memory(), it > makes sense to add all memory to the memblock memory table, and simply mark > it as MEMBLOCK_NOMAP if it lacks the EFI_MEMORY_WB attribute. > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > --- > > Note that this will also result in regions with EFI_MEMORY_WB cleared to > be listed in /proc/iomem as 'System RAM', which may be incorrect. However, > we already display this incorrect behavior for runtime services code/data > regions, so this should be fixed in a separate patch, of which an example > has been proposed here: > https://www.spinics.net/lists/arm-kernel/msg525369.html > > drivers/firmware/efi/arm-init.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c > index c49d50e68aee..678672d332f8 100644 > --- a/drivers/firmware/efi/arm-init.c > +++ b/drivers/firmware/efi/arm-init.c > @@ -28,7 +28,7 @@ u64 efi_system_table; > > static int __init is_normal_ram(efi_memory_desc_t *md) > { > - if (md->attribute & EFI_MEMORY_WB) > + if (md->attribute & (EFI_MEMORY_WB|EFI_MEMORY_WT|EFI_MEMORY_WC)) The code change makes a lot of sense, but this makes the call sites a bit confusing. It would make sense to rename this function. Would supports_unaligned() be too silly? That's basically what the above makes it mean. / Leif > return 1; > return 0; > } > @@ -163,7 +163,13 @@ static __init int is_reserve_region(efi_memory_desc_t *md) > case EFI_BOOT_SERVICES_DATA: > case EFI_CONVENTIONAL_MEMORY: > case EFI_PERSISTENT_MEMORY: > - return 0; > + /* > + * According to the spec, these regions are no longer reserved > + * after calling ExitBootServices(). However, we can only use > + * them as System RAM if they can be mapped writeback cacheable. > + * Otherwise, treat them as reserved. > + */ > + return (md->type & EFI_MEMORY_WB) == 0; > default: > break; > } > -- > 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
