On Sunday 24 January 2016 02:54 AM, Paul Mackerras wrote: > On Sat, Jan 23, 2016 at 06:23:35PM +0530, Aravinda Prasad wrote: >> >> >> On Saturday 23 January 2016 03:58 PM, Paul Mackerras wrote: >>> On Wed, Jan 13, 2016 at 12:38:09PM +0530, Aravinda Prasad wrote: >>>> Enhance KVM to cause a guest exit with KVM_EXIT_NMI >>>> exit reasons upon a machine check exception (MCE) in >>>> the guest address space if the KVM_CAP_PPC_FWNMI >>>> capability is enabled (instead of delivering 0x200 >>>> interrupt to guest). This enables QEMU to build error >>>> log and deliver machine check exception to guest via >>>> guest registered machine check handler. >>>> >>>> This approach simplifies the delivering of machine >>>> check exception to guest OS compared to the earlier >>>> approach of KVM directly invoking 0x200 guest interrupt >>>> vector. In the earlier approach QEMU was enhanced to >>>> patch the 0x200 interrupt vector during boot. The >>>> patched code at 0x200 issued a private hcall to pass >>>> the control to QEMU to build the error log. >>>> >>>> This design/approach is based on the feedback for the >>>> QEMU patches to handle machine check exception. Details >>>> of earlier approach of handling machine check exception >>>> in QEMU and related discussions can be found at: >>> >>> [snip] >>> >>>> --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S >>>> +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S >>>> @@ -133,21 +133,18 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S) >>>> stb r0, HSTATE_HWTHREAD_REQ(r13) >>>> >>>> /* >>>> - * For external and machine check interrupts, we need >>>> - * to call the Linux handler to process the interrupt. >>>> - * We do that by jumping to absolute address 0x500 for >>>> - * external interrupts, or the machine_check_fwnmi label >>>> - * for machine checks (since firmware might have patched >>>> - * the vector area at 0x200). The [h]rfid at the end of the >>>> - * handler will return to the book3s_hv_interrupts.S code. >>>> - * For other interrupts we do the rfid to get back >>>> - * to the book3s_hv_interrupts.S code here. >>>> + * For external interrupts we need to call the Linux >>>> + * handler to process the interrupt. We do that by jumping >>>> + * to absolute address 0x500 for external interrupts. >>>> + * The [h]rfid at the end of the handler will return to >>>> + * the book3s_hv_interrupts.S code. For other interrupts >>>> + * we do the rfid to get back to the book3s_hv_interrupts.S >>>> + * code here. >>>> */ >>>> ld r8, 112+PPC_LR_STKOFF(r1) >>>> addi r1, r1, 112 >>>> ld r7, HSTATE_HOST_MSR(r13) >>>> >>>> - cmpwi cr1, r12, BOOK3S_INTERRUPT_MACHINE_CHECK >>>> cmpwi r12, BOOK3S_INTERRUPT_EXTERNAL >>>> beq 11f >>>> cmpwi r12, BOOK3S_INTERRUPT_H_DOORBELL >>>> @@ -162,7 +159,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S) >>>> mtmsrd r6, 1 /* Clear RI in MSR */ >>>> mtsrr0 r8 >>>> mtsrr1 r7 >>>> - beq cr1, 13f /* machine check */ >>>> RFI >>>> >>>> /* On POWER7, we have external interrupts set to use HSRR0/1 */ >>>> @@ -170,8 +166,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S) >>>> mtspr SPRN_HSRR1, r7 >>>> ba 0x500 >>>> >>>> -13: b machine_check_fwnmi >>>> - >>> >>> So, what you're disabling here is the host-side handling of the >>> machine check after completing the guest->host switch. This has >>> nothing to do with how the machine check gets communicated to the >>> guest. >>> >>> Now, part of the host-side machine check handling has already >>> happened, but I thought there was more that was done in host kernel >>> virtual mode. If this change really is needed then I would want an >>> ack from Mahesh that this is correct, and it will need to be explained >>> in detail in the patch description. >> >> If we don't do that we will end up running into >> panic() in opal_machine_check() if UE belonged to guest. >> >> Details in this link: >> http://marc.info/?l=kvm-ppc&m=144730552720044&w=2 > > Well maybe the panic call needs to be changed. But the way you have > it, we *never* get to opal_machine_check for any machine check > interrupt, and I have a hard time believing that is correct.
If I am not wrong, earlier, even without this patch we never get to opal_machine_check() from this place for the machine check happening inside the guest (irrespective of whether the machine check is recovered or not). Because, we jump to fast_interrupt_c_return() from machine_check_realmode without causing the guest to exit. With this patch I call mc_cont from machine_check_realmode and want the guest to exit with NMI exit code. However, we don't want to call opal_machine_check(), because if we call opal_machine_check() we don't end up with NMI exit for the guest. Regards, Aravinda > > Paul. > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/linuxppc-dev > -- Regards, Aravinda _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
