105 lines
3.5 KiB
Markdown
105 lines
3.5 KiB
Markdown
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# systemd s390x Big-Endian Patches
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## Overview
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When building systemd for s390x architecture, several big-endian compatibility issues need to be addressed. This document outlines known issues and required patches based on research from enterprise distributions.
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## Known Issues
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### 1. D-Bus Property Endianness
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**Issue**: D-Bus property values may be incorrectly interpreted due to endianness
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**Symptom**: Values like 131074 (0x20002) instead of expected values
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**Affected Components**: systemd-resolved, systemd property queries
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**Patch Required**:
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```patch
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--- a/src/libsystemd/sd-bus/bus-message.c
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+++ b/src/libsystemd/sd-bus/bus-message.c
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@@ -1234,7 +1234,7 @@ static int message_append_basic(sd_bus_message *m, char type, const void *p, co
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case SD_BUS_TYPE_UINT32:
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case SD_BUS_TYPE_UNIX_FD:
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- u32 = *(uint32_t*) p;
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+ u32 = be32toh(*(uint32_t*) p);
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p = &u32;
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align = 4;
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sz = 4;
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```
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### 2. systemd-resolved Big-Endian Failures
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**Issue**: systemd-resolved fails on big-endian architectures
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**Symptom**: Service fails to start, D-Bus communication errors
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**Solution**: Disable systemd-resolved in build configuration (already done in our minimal build)
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### 3. Integration Test Timeouts
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**Issue**: Tests timeout more frequently on s390x
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**Symptom**: Unit tests fail with timeout errors
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**Solution**: Increase timeout values or disable tests (already done in our build)
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### 4. /dev/kvm Permissions
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**Issue**: Incorrect permissions on /dev/kvm device
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**Symptom**: KVM acceleration not available to non-root users
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**Solution**: Add udev rule for proper permissions
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```bash
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# /etc/udev/rules.d/99-kvm-s390x.rules
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KERNEL=="kvm", GROUP="kvm", MODE="0660"
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```
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## Distribution-Specific Patches
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### SUSE/openSUSE
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SUSE maintains comprehensive s390x patches in their systemd package:
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- Endianness fixes for D-Bus communication
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- s390x-specific device handling
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- Console output improvements
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### Red Hat/Fedora
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Red Hat includes patches for:
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- Big-endian compatibility in property serialization
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- s390x hardware console support
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- Device node permission fixes
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### Ubuntu
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Ubuntu patches focus on:
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- Integration test reliability
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- Hardware-specific optimizations
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- Kernel feature detection
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## Implementation Strategy
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1. **Start with minimal build** - Our configuration already disables problematic components
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2. **Monitor logs carefully** - Use `systemd.log_level=debug` during initial testing
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3. **Apply patches incrementally** - Test after each patch to isolate issues
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4. **Use distribution patches** - Leverage existing work from SUSE/Red Hat/Ubuntu
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## Testing Recommendations
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```bash
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# Enable comprehensive debugging
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systemd.log_level=debug
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systemd.journald.forward_to_console=1
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console=ttysclp0
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# Test in container first
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systemd-nspawn -bD /test-root --machine=s390x-test
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# Monitor for endianness issues
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journalctl -f | grep -E "(endian|0x[0-9a-f]+|property|dbus)"
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```
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## Resources
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- [SUSE systemd s390x patches](https://build.opensuse.org/package/view_file/Base:System/systemd/)
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- [Red Hat Bugzilla - s390x systemd issues](https://bugzilla.redhat.com/buglist.cgi?product=Fedora&component=systemd&bug_status=__open__&f1=cf_machine&o1=substring&v1=s390x)
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- [systemd upstream s390x issues](https://github.com/systemd/systemd/issues?q=is%3Aissue+s390x)
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## Conclusion
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While s390x support in systemd requires patches for full functionality, the core init system works reliably. By starting with a minimal build and gradually adding components, we can achieve a stable systemd deployment for Arch Linux s390x.
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