On 12/05/19 17:50, Ard Biesheuvel wrote: > On Thu, 5 Dec 2019 at 16:27, Philippe Mathieu-Daudé <phi...@redhat.com> wrote: >> >> On 12/5/19 5:13 PM, Laszlo Ersek wrote: >>> Hi Phil, >>> >>> (+Ard) >>> >>> On 12/04/19 23:12, Philippe Mathieu-Daudé wrote: >>>> Centos 7.7 only provides cross GCC 4.8.5, but the script forces >>>> us to use GCC5. Since the same machinery is valid to check the >>>> GCC version, remove the $emulation_target check. >>>> >>>> $ cat /etc/redhat-release >>>> CentOS Linux release 7.7.1908 (Core) >>>> >>>> $ aarch64-linux-gnu-gcc -v 2>&1 | tail -1 >>>> gcc version 4.8.5 20150623 (Red Hat 4.8.5-16) (GCC) >>> >>> this patch is not correct, in my opinion. ARM / AARCH64 support in edk2 >>> requires GCC5 as a minimum. It was never tested with an earlier >>> toolchain, to my understanding. Not on my part, anyway. >>> >>> To be more precise: when I tested cross-gcc toolchains earlier than >>> that, the ArmVirtQemu builds always failed. Minimally, those toolchains >>> didn't recognize some of the AARCH64 system registers. >>> >>> If CentOS 7.7 does not provide a suitable (>=GCC5) toolchain, then we >>> can't build ArmVirtQemu binaries on CentOS 7.7, in my opinion. >>> >>> Personally, on my RHEL7 laptop, over time I've used the following >>> toolchains, to satisfy the GCC5 requirement of ArmVirtQemu (which >>> requirement I took as experimental evidence): >>> >>> - Initially (last quarter of 2014), I used binary distributions -- >>> tarballs -- of cross-binutils and cross-gcc, from Linaro. >>> >>> - Later (last quarter of 2016), I rebuilt some SRPMs that were at the >>> time Fedora-only for RHEL7. Namely: >>> >>> - cross-binutils-2.27-3.fc24 >>> https://koji.fedoraproject.org/koji/buildinfo?buildID=801348 >>> >>> - gcc-6.1.1-2.fc24 >>> https://koji.fedoraproject.org/koji/buildinfo?buildID=761767 >>> >>> - Most recently, I've been using cross-binutils updated from EPEL7: >>> >>> - cross-binutils-2.27-9.el7.1 >>> https://koji.fedoraproject.org/koji/buildinfo?buildID=918474 >>> >>> To my knowledge, there is still no suitable cross-compiler available on >>> RHEL7, from any trustworthy RPM repository. So, to this day, I use >>> gcc-6.1.1-2 for cross-building ArmVirtQemu, on my RHEL7 laptop. >>> >>> Again: I believe it does not matter if the gcc-4.8.5-based >>> cross-compiler in CentOS 7 "happens" to work. That's a compiler that I >>> have never tested with, or vetted for, upstream ArmVirtQemu. >>> >>> Now, I realize that in edk2, we have stuff like >>> >>> GCC48_AARCH64_CC_FLAGS >>> >>> in "BaseTools/Conf/tools_def.template" -- coming from commit >>> 7a9dbf2c94d1 ("BaseTools/Conf/tools_def.template: drop ARM/AARCH support >>> from GCC46/GCC47", 2019-01-08). That doesn't change the fact that I've >>> never built or tested ArmVirtQemu with such a compiler. And so this >>> patch makes me quite uncomfortable. >>> >>> If that rules out CentOS 7 as a QEMU project build / CI platform for the >>> bundled ArmVirtQemu binaries, then we need a more recent platform >>> (perhaps CentOS 8, not sure). >> >> Unfortunately CentOS 8 is not available as a Docker image, which is a >> convenient way to build EDK2 in a CI. >> >>> I think it's also educational to check the origin of the code that your >>> patch proposes to remove. Most recently it was moved around from a >>> different place, in QEMU commit 65a109ab4b1a ('roms: lift >>> "edk2-funcs.sh" from "tests/uefi-test-tools/build.sh"', 2019-04-17). >>> >>> In that commit, for some reason I didn't keep the original code comments >>> (perhaps it would have been too difficult or messy to preserve the >>> comments sanely with the restructured / factored-out code). But, they >>> went like this (originally from commit 77db55fc8155, >>> "tests/uefi-test-tools: add build scripts", 2019-02-21): >>> >>> # Expose cross_prefix (which is possibly empty) to the edk2 tools. While at >>> it, >>> # determine the suitable edk2 toolchain as well. >>> # - For ARM and AARCH64, edk2 only offers the GCC5 toolchain tag, which >>> covers >>> # the gcc-5+ releases. >>> # - For IA32 and X64, edk2 offers the GCC44 through GCC49 toolchain tags, in >>> # addition to GCC5. Unfortunately, the mapping between the toolchain tags >>> and >>> # the actual gcc releases isn't entirely trivial. Run "git-blame" on >>> # "OvmfPkg/build.sh" in edk2 for more information. >>> # And, because the above is too simple, we have to assign cross_prefix to an >>> # edk2 build variable that is specific to both the toolchain tag and the >>> target >>> # architecture. >>> >>> So... unless Ard feels it is really totally safe to retro-actively rely >>> on the gcc-4.8.5-based compiler in CentOS 7, I'd rather we picked a more >>> recent build platform (OS) instead. For example, we build ArmVirtQemu on >>> RHEL8 regularly, so that's a reality-based "plus" for CentOS 8. >>> >>> >>> Independently of all of the above, the OVMF toolchain selection logic >>> that this patch proposes to reuse with ArmVirtQemu, is *really* >>> x86-specific. Please run "git blame" on "OvmfPkg/build.sh" in upstream >>> edk2, to see where the various branches come from (as the comments in >>> this shell script suggest as well). There had been mess like commit >>> 656ac0c7d8ea ('Revert "OvmfPkg/build.sh: select the GCC49 toolchain >>> settings for gcc-7.*"', 2017-08-25). >> >> Thanks for all the pointers, very educative indeed :) >> >> I'll see other setups I can use with GCC5+ available. >> >> I still have to figure if there are free tier CI with less limitations >> than Travis/Shippable/GitLab, so we can keep the full EDK2 build output log. >> > > My CI job for ArmVirtQemu/EDK2 build tested GCC48 and GCC49 until very > recently, and I never experienced any issues when running those > images, although it's been much longer that I actually tried that. So > I wouldn't recommend against it, and if we do identify any issues, we > should either deprecate GCC48 (for ArmVirtQemu or for AArch64 > altogether) or fix them. >
OK, thank you, I'm fully satisfied with this addition. :) Phil, in this case I think we can indeed replace the hard-coded "GCC5" with a bit of dynamic detection. Two remarks: - Please CC Ard on v2, so he can ACK. I'd like that. :) - Again, we shouldn't blindly reapply the x86 (OVMF) quirk(s). I mean mainly the special casing of "6.[0-2].*" to GCC49, which comes from upstream edk2 commit 432f1d83f77a ("OvmfPkg/build.sh: Use GCC49 toolchains with GCC 6.[0-2]", 2016-12-06). ... or is that GCC bug target-independent in fact? I can't really tell; the upstream GCC bug <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70955> is ISA-specific (x86-64), and so are function calling conventions. I'd suggest *not* applying the quirk for ArmVirtQemu, initially. Thanks Laszlo