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? Laszlo -- 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
