On Thu, Jul 30, 2020 at 1:19 PM Heinrich Schuchardt <xypron.g...@gmx.de> wrote: > > Am 30. Juli 2020 22:11:39 MESZ schrieb Heinrich Schuchardt > <xypron.g...@gmx.de>: > >Am 30. Juli 2020 20:31:47 MESZ schrieb Atish Patra > ><ati...@atishpatra.org>: > >>On Thu, Jul 30, 2020 at 4:04 AM Heinrich Schuchardt > >><xypron.g...@gmx.de> wrote: > >>> > >>> On 30.07.20 12:16, Sean Anderson wrote: > >>> > On 7/30/20 6:03 AM, Heinrich Schuchardt wrote: > >>> >> Dear Sean, > >>> >> > >>> >> when trying to run grubriscv64.efi from the > >>> >> trini/u-boot-gitlab-ci-runner:bionic-20200526-18Jun2020 Docker > >>image on > >>> >> a MAIXDUINO the relocations are not naturally aligned: > >>> >> > >>> >> lib/efi_loader/efi_image_loader.c(133) efi_loader_relocate(): > >>> >> > >>> >> efi_reloc 000000008030a000, offset 0x101e, type 10 > >>> >> > >>> >> Here we are trying to change an u64 at 0x8030B01E: > >>> >> > >>> >> uint64_t *x64 = efi_reloc + offset; > >>> >> *x64 += (uint64_t)delta; > >>> >> > >>> >> This leads to an exception in function efi_loader_relocate(): > >>> >> > >>> >> Unhandled exception: Load address misaligned > >>> >> EPC: 00000000805a95ac RA: 00000000805a953a TVAL: > >>000000008030b01e > >>> >> EPC: 000000008001c5ac RA: 000000008001c53a reloc > >>> >> > >>> >> The GRUB image is available here: > >>> >> > >>> >> > >>https://gist.github.com/xypron/522a91962248e9c3888d8554cb61ad2c/raw/b959661626b38a738673a9efb2f398b2fabd5c77/grubriscv64.efi > >>> >> > >>> >> On QEMU the GRUB image is executed without problems: > >>> >> > >>> >> https://gitlab.denx.de/u-boot/custodians/u-boot-efi/-/jobs/132919 > >>> >> > >>> >> The UEFI specification requires for the ARM platform that > >>unaligned > >>> >> support is enabled. This is why we have implemented function > >>> >> allow_unaligned(). > >>> >> > >>> >> On RISC-V we have not yet implemented allow_unaligned() yet. Is > >>there a > >>> >> way to switch RISCV64 CPUs especially the Kendryte K210 into a > >>mode > >>> >> supporting unaligned access? > >>> > > >>> > AFAIK RISC-V has no requirement that un-aligned loads/stores > >>complete. I > >>> > believe the recommended solution is to install a trap handler > >which > >>> > completes the un-aligned load through a series of aligned loads > >and > >>then > >>> > returns back to the application. For an example of such an > >>> > implementation, check out arch/riscv/kernel/traps_misaligned.c in > >>Linux. > >>> > This may be too complex for U-Boot, so perhaps you can simply > >>disallow > >>> > unaligned accesses? > >>> > > >>> > --Sean > >>> > > >>> > >>> Working around the problem inside U-Boot is easy (just some memcpy() > >>> calls) but the GRUB image itself also makes unaligned accesses: > >>> > >>> Unhandled exception: Load address misaligned > >>> EPC: 000000008030b004 RA: 00000000805a4eca TVAL: 000000008030b02e > >>> EPC: 000000007fd7e004 RA: 0000000080017eca reloc > >>> > >>> UEFI image [0x000000008030a000:0x0000000080433fff] pc=0x1004 > >>> > >>> This is what I found in "RISC-V Unprivileged ISA V20191213" > >>> > >>> "Loads and stores where the effective address is not > >>naturally > >>> aligned to the referenced datatype (i.e., on a four-byte boundary > >for > >>> 32-bit accesses, and a two-byte boundary for 16-bit accesses) have > >>> behavior dependent on the EEI. An EEI may guarantee that misaligned > >>> loads and stores are fully supported, and so the software running > >>inside > >>> the execution environment will never experience a contained or fatal > >>> address-misaligned trap." > >>> > >>> @Leif > >>> Should GRUB be built with -mstrict-align for RISC-V? > >>> > >> > >>That shouldn't be necessary. Any real board with an MMU that can boot > >>Linux needs > >>a SBI provider such as OpenSBI. OpenSBI already implements a > >misaligned > >>handler. > >> > >>Are we planning to support EFI booting for NoMMU platforms ? As per my > >>understanding > >>runtime services need to be mapped through kernel page tables. > >> > > > >My interest is to have an affordable hardware platform where I can test > >U-Boot's UEFI sub-system on RISC-V. > >
Yeah. For U-Boot UEFI subsystem verification kendryte is a good choice. But we shouldn't try to boot Linux via grub on that platform :) > >With 6 MiB usable RAM. (2 MiB reserved for AI) we probably won't get > >further than running GRUB. > > > >Can OpenSBI be built for the Kendryte K210 SoC? What is the size of > >OpenSBI? > Usually, OpenSBI firmware size is around ~100 KB. > Yes: > https://github.com/riscv/opensbi/tree/master/platform/kendryte/k210 > > So we should try if we can run U-Boot with OpenSBI on the platform. > > > > >Best regards > > > >Heinrich > > > >>> @Ard > >>> How about the EFI part of the Linux kernel? > >>> > >>> Best regards > >>> > >>> Heinrich > -- Regards, Atish _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel
