On 7/29/21 8:14 AM, Philippe Mathieu-Daudé wrote: > On 7/29/21 2:46 AM, Richard Henderson wrote: >> This began with Peter wanting a cpu_ldst.h interface that can handle >> alignment info for Arm M-profile system mode, which will also compile >> for user-only without ifdefs. This is patch 32. >> >> Once I had that interface, I thought I might as well enforce the >> requested alignment in user-only. There are plenty of cases where >> we ought to have been doing that for quite a while. This took rather >> more work than I imagined to start. >> >> So far only x86 host has been fully converted to handle unaligned >> operations in user-only mode. I'll get to the others later. But >> the added testcase is fairly broad, and caught lots of bugs and/or >> missing code between target/ and linux-user/. >> >> Notes: >> * For target/i386 we have no way to signal SIGBUS from user-only. >> In theory we could go through do_unaligned_access in system mode, >> via #AC. But we don't even implement that control in tcg, probably >> because no one ever sets it. The cmpxchg16b insn requires alignment, >> but raises #GP, which maps to SIGSEGV. >> >> * For target/s390x we have no way to signal SIGBUS from user-only. >> The atomic operations raise PGM_SPECIFICATION, which the linux >> kernel maps to SIGILL. >> >> * I think target/hexagon should be setting TARGET_ALIGNED_ONLY=y. >> In the meantime, all memory accesses are allowed to be unaligned. > > Now I better understand what you tried to explain me last with > TCGCPUOps. Since Claudio was also involved, Cc'ing him (not asking > for a review, just in case he wants to follow up). >
Thanks, what I understand from glancing through the thread is that at the time we made handling of unaligned access a sysmmu-only TCGCPUOps, while this series corrects that and implements unaligned accesses for user-only, so seems good to me. Ciao, Claudio
