On 24.11.2012, at 09:37, Paul Mackerras wrote: > Currently, if a machine check interrupt happens while we are in the > guest, we exit the guest and call the host's machine check handler, > which tends to cause the host to panic. Some machine checks can be > triggered by the guest; for example, if the guest creates two entries > in the SLB that map the same effective address, and then accesses that > effective address, the CPU will take a machine check interrupt. > > To handle this better, when a machine check happens inside the guest, > we call a new function, kvmppc_realmode_machine_check(), while still in > real mode before exiting the guest. On POWER7, it handles the cases > that the guest can trigger, either by flushing and reloading the SLB, > or by flushing the TLB, and then it delivers the machine check interrupt > directly to the guest without going back to the host. On POWER7, the > OPAL firmware patches the machine check interrupt vector so that it > gets control first, and it leaves behind its analysis of the situation > in a structure pointed to by the opal_mc_evt field of the paca. The > kvmppc_realmode_machine_check() function looks at this, and if OPAL > reports that there was no error, or that it has handled the error, we > also go straight back to the guest with a machine check. We have to > deliver a machine check to the guest since the machine check interrupt > might have trashed valid values in SRR0/1. > > If the machine check is one we can't handle in real mode, and one that > OPAL hasn't already handled, or on PPC970, we exit the guest and call > the host's machine check handler. We do this by jumping to the > machine_check_fwnmi label, rather than absolute address 0x200, because > we don't want to re-execute OPAL's handler on POWER7. On PPC970, the > two are equivalent because address 0x200 just contains a branch. > > Then, if the host machine check handler decides that the system can > continue executing, kvmppc_handle_exit() delivers a machine check > interrupt to the guest -- once again to let the guest know that SRR0/1 > have been modified. > > Signed-off-by: Paul Mackerras <paulus@xxxxxxxxx> Thanks for the semantic explanations :). From that POV things are clear and good with me now. That leaves only checkpatch ;) WARNING: please, no space before tabs #142: FILE: arch/powerpc/kvm/book3s_hv_ras.c:21: +#define SRR1_MC_IFETCH_SLBMULTI ^I3^I/* SLB multi-hit */$ WARNING: please, no space before tabs #143: FILE: arch/powerpc/kvm/book3s_hv_ras.c:22: +#define SRR1_MC_IFETCH_SLBPARMULTI ^I4^I/* SLB parity + multi-hit */$ WARNING: min() should probably be min_t(u32, slb->persistent, SLB_MIN_SIZE) #168: FILE: arch/powerpc/kvm/book3s_hv_ras.c:47: + n = min(slb->persistent, (u32) SLB_MIN_SIZE); total: 0 errors, 3 warnings, 357 lines checked Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
