Am 01.12.2012 12:26, schrieb Peter Maydell: > On 30 November 2012 21:38, Eduardo Habkost <ehabk...@redhat.com> wrote: >> cpu_reset() is not that well-defined, otherwise we wouldn't have this on >> linux-user: >> >> #if defined(TARGET_I386) || defined(TARGET_SPARC) || defined(TARGET_PPC) >> cpu_reset(ENV_GET_CPU(env)); >> #endif >> >> (I have no idea why we have that #ifdef). > > I think this is because the different targets disagree about whether > the CPU should be reset on initial construction or whether it needs > a specific reset call. (The current setup with #ifdefs is among other > things a historical effect as a result of various refactorings in > the past; you can trace the git history if you're interested.)
Peter and me had long IRC discussions about how to fix this in the past: * On my qom-cpu-copy branch I have a patch queued that drops the #ifdef above, accepting that CPUs may get reset twice then. => Dispels doubt for target authors; doubts about correctness though. * PMM suggested to move cpu_clone_regs() from target-*/cpu.h to *-user/. => Would lead to duplication between linux-user and bsd-user; ABI? * PMM suggested to replace cpu_copy() with ABI-specific code in *-user/. Unfortunately I don't quite remember the details of how... ;) The x86 APIC refactorings that Iguardo have done do bring us very close to sane cpu_reset() semantics (ignoring the two hands full of hard/soft/... reset variants that ppc and other architectures feature). Declaring cpu_reset() inferior to reset handlers due to the linux-user mess is going into the wrong direction - some targets seem to ignore reset or fork/clone completely at the moment, so the state we see cannot be considered fully correct. In particular the above reset is being performed *after* cpu_copy() memcpy()'ed random memory contents (which for some targets may contain pointers), undoing the copying in large parts. Therefore, when all targets reset as part of cpu_init() (or by moving the cpu_reset() call into early cpu_copy()?) we could get rid of it in do_fork() and of its weird conditions. Andreas -- SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg
