On Mon, Sep 16, 2013 at 06:25:22PM +0200, Laszlo Ersek wrote: > On 09/16/13 17:57, Josh Triplett wrote: > > >> The edk2 commit that flipped the memory type underneath the image data > >> from EfiReservedMemoryType to EfiBootServicesData is: > >> > >> https://github.com/tianocore/edk2/commit/4c58575e > >> > >> I think this commit is wrong. It's fine for OSPM to release the image > >> data at some point, but not right after ExitBootServices(), because > >> referencing pointers in ACPI tables survive strictly longer. > >> > >> ... Actually, the commit does follow the ACPI spec 5.0: > >> > >> 5.2.22.4 Image Address > >> > >> The Image Address contains the location in memory where an > >> in-memory copy of the boot image can be found. The image should be > >> stored in EfiBootServicesData, allowing the system to reclaim > >> the memory when the image is no longer needed. > >> > >> The ACPI spec 5.0 should recommend EfiACPIReclaimMemory here IMO. (I > >> take the current wording ("should be stored") as a recommendation only.) > > > > I agree that UEFI *should* store the BGRT in EfiACPIReclaimMemory, but > > in practice the UEFI firmware I've seen with a BGRT does follow that > > recommendation and store it in EfiBootServicesData. So, even if the > > recommendation in the spec changed, the kernel would still have to > > accomodate both possibilities. > > Just for the theoretical debate: > > The edk2 commit linked above is 5 days old. All UEFI firmware in the > wild (on released hardware) should be using EfiReservedMemoryType (the > pre-patch memory type), which is even stricter. > > EfiReservedMemoryType can never be released & repurposed, so it should > make no difference for crash kernel allocation, shouldn't it? > > - call efi_free_boot_services() -- doesn't touch the image data (which > is in RAM of EfiReservedMemoryType), > - reserve crash kernel, > - access BGRT via ACPI. > > BGRT had appeared in edk2 with > > https://github.com/tianocore/edk2/commit/0284e90c > > and EfiReservedMemoryType used to be the allocation type until commit > 4c58575e. > > Or are you alluding to UEFI firmware that's not based on TianoCore? I'm saying, in practice, that the systems I tested BGRT support on and submitted patches for stored the BGRT's image in EfiBootServicesData. - Josh Triplett -- 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
