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QEMU tracks whether a vcpu is halted using CPUState::halted. E.g., after initialization or reset, halted is 0 for the BSP (vcpu 0) and 1 for the APs (vcpu 1, 2, ...). A halted vcpu should not be handed to the hypervisor to run (e.g. hax_vcpu_run()). Under HAXM, Android Emulator sometimes boots into a "vcpu shutdown request" error while executing in SeaBIOS, with the HAXM driver logging a guest triple fault in vcpu 1, 2, ... at RIP 0x3. That is ultimately because the HAX accelerator asks HAXM to run those APs when they are still in the halted state. Normally, the vcpu thread for an AP will start by looping in qemu_wait_io_event(), until the BSP kicks it via a pair of IPIs (INIT followed by SIPI). But because the HAX accelerator does not honor cpu->halted, it allows the AP vcpu thread to proceed to hax_vcpu_run() as soon as it receives any kick, even if the kick does not come from the BSP. It turns out that emulator has a worker thread which periodically kicks every vcpu thread (possibly to collect CPU usage data), and if one of these kicks comes before those by the BSP, the AP will start execution from the wrong RIP, resulting in the aforementioned SMP boot failure. The solution is inspired by the KVM accelerator (credit to Chuanxiao Dong <chuanxiao.dong@intel.com> for the pointer): 1. Get rid of questionable logic that unconditionally resets cpu->halted before hax_vcpu_run(). Instead, only reset it at the right moments (there are only a few "unhalt" events). 2. Add a check for cpu->halted before hax_vcpu_run(). Note that although the non-Unrestricted Guest (!ug_platform) code path also forcibly resets cpu->halted, it is left untouched, because only the UG code path supports SMP guests. The patch is first merged to android emulator with Change-Id: I9c5752cc737fd305d7eace1768ea12a07309d716 Cc: Yu Ning <yu.ning@intel.com> Cc: Chuanxiao Dong <chuanxiao.dong@intel.com> Signed-off-by: Colin Xu <colin.xu@intel.com> Message-Id: <20190610021939.13669-1-colin.xu@intel.com> |
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| .. | ||
| hvf | ||
| arch_dump.c | ||
| arch_memory_mapping.c | ||
| bpt_helper.c | ||
| cc_helper_template.h | ||
| cc_helper.c | ||
| cpu-param.h | ||
| cpu-qom.h | ||
| cpu.c | ||
| cpu.h | ||
| excp_helper.c | ||
| fpu_helper.c | ||
| gdbstub.c | ||
| hax-all.c | ||
| hax-i386.h | ||
| hax-interface.h | ||
| hax-mem.c | ||
| hax-posix.c | ||
| hax-posix.h | ||
| hax-windows.c | ||
| hax-windows.h | ||
| helper.c | ||
| helper.h | ||
| hyperv-proto.h | ||
| hyperv-stub.c | ||
| hyperv.c | ||
| hyperv.h | ||
| int_helper.c | ||
| kvm_i386.h | ||
| kvm-stub.c | ||
| kvm.c | ||
| machine.c | ||
| Makefile.objs | ||
| mem_helper.c | ||
| misc_helper.c | ||
| monitor.c | ||
| mpx_helper.c | ||
| ops_sse_header.h | ||
| ops_sse.h | ||
| seg_helper.c | ||
| sev_i386.h | ||
| sev-stub.c | ||
| sev.c | ||
| shift_helper_template.h | ||
| smm_helper.c | ||
| svm_helper.c | ||
| svm.h | ||
| TODO | ||
| trace-events | ||
| translate.c | ||
| whp-dispatch.h | ||
| whpx-all.c | ||
| xsave_helper.c | ||