On Thu, Sep 30, 2021 at 2:23 PM François Ozog <francois.o...@linaro.org> wrote:
> > > Le jeu. 30 sept. 2021 à 07:12, Bin Meng <bmeng...@gmail.com> a écrit : > >> Hi Heinrich, >> >> On Thu, Sep 9, 2021 at 7:16 PM Heinrich Schuchardt <xypron.g...@gmx.de> >> wrote: >> > >> > Hello Simon, >> > >> > The EBBR specification requires that the UEFI SystemReset() runtime >> > service is available to the operating system. >> > >> > Up to now this has been implemented by overriding function >> > efi_reset_system() which is marked as __efi_runtime. >> > >> > Both ARM and RISC-V support generic interfaces for reset. PSCI for ARM >> > and the System Reset Extension for SBI on RISC-V. This has kept the >> > number of implementations low. The only exceptions are: >> > >> > * arch/arm/cpu/armv8/fsl-layerscape/cpu.c >> > * arch/arm/mach-bcm283x/reset.c for the Raspberry PIs >> > * arch/sandbox/cpu/start.c >> > >> > Bin has suggested in >> > https://lists.denx.de/pipermail/u-boot/2021-September/459865.html to >> use >> > reset drivers based on the driver model. >> > >> > Currently after ExitBootServices() the driver model does not exist >> anymore. >> > >> > When evaluating Bin's suggestion one has to keep in mind that after >> > invoking ExitBootServices() most operating systems call >> > SetVirtualAddressMap(). Due to the change of the address map all >> > pointers used by U-Boot afterwards must be updated to match the new >> > memory map. >> > >> >> Yeah, this was discussed 3 years ago: >> >> https://u-boot.denx.narkive.com/mA8xIbLk/efi-loader-runtime-services-implementation-broken >> >> > The impression that Ilias and I have is that keeping the driver model >> > alive after SetVirtualAddressMap() would incur: >> > >> > * a high development effort >> > * a significant code size increase >> > * an enlarged attack surface >> > >> > For RISC-V it has been clarified in the platform specification that the >> > SBI must implement the system reset extension. For ARMv8 using TF-A and >> > PSCI is what ARM suggests. >> > >> > So for these architectures we do not expect a growth in the number of >> > drivers needed. >> > >> > Ilias and my favorite would be keeping the design as is. >> > >> > What is your view on this? >> >> Is U-Boot's UEFI loader implementation supposed to be the recommended >> UEFI firmware on ARM and RISC-V on a production / deployment system? > > For Arm: yes, that is SystemReady spec. > How about EDK II? Is EDK II supposed to be used in the server environment where UEFI + ACPI is the way to go? Does any board that ships EDK II with UEFI + DTB? Can we safely assume that U-Boot's UEFI loader is the reference implementation for UEFI + DTB on Arm? > >> Do we expect bootefi to boot a kernel with CONFIG_EFI_STUB, or do we >> expect to load grub.efi which chain-loads a kernel without >> CONFIG_EFI_STUB? > > all paths should be possible , and the shim.efi is to be supported too. > With UEFI, I always see that UEFI is kept down to OS for SecureBoot. In > other words I don’t see grub.efi booting a non config_efi_stub. > >> What do distributions normally do? > > At least Red Hat made it clear at multiple Linaro Connect that they want > standards, and SystemReady is one that makes the life of embedded distros > easy. > Distros boot shim.efi, grub.efi, Linux.efi to benefit from UEFi SecureBoot. > >> What's our >> position when compared to EDK II? > > the typical distro boot flow is not the most efficient and drags concept > dating where the Microsoft certs had to be part of the picture. A direct > U-Boot Linux.efi is my preferred; avoids yet another OS in the boot path > (grub), avoids convoluted platform cert management (shim) and just enhance > security and boot time. Note: Since kernel 5.10, initrd can be measured > (with TPM) when loaded by efi-stub. > Regards, Bin
