On 28.08.14 19:42, Aravinda Prasad wrote: > > > On Thursday 28 August 2014 02:07 PM, Alexander Graf wrote: >> >> >> On 28.08.14 08:38, Aravinda Prasad wrote: >>> >>> >>> On Wednesday 27 August 2014 04:07 PM, Alexander Graf wrote: >>>> >>>> >>>> On 25.08.14 15:45, Aravinda Prasad wrote: >>>>> This patch adds FWNMI support in qemu for powerKVM >>>>> guests by handling the ibm,nmi-register rtas call. >>>>> Whenever OS issues ibm,nmi-register RTAS call, the >>>>> machine check notification address is saved and the >>>>> machine check interrupt vector 0x200 is patched to >>>>> issue a private hcall. >>>>> >>>>> Signed-off-by: Aravinda Prasad <aravi...@linux.vnet.ibm.com> >>>>> --- >>>>> hw/ppc/spapr_rtas.c | 91 >>>>> ++++++++++++++++++++++++++++++++++++++++++++++++ >>>>> include/hw/ppc/spapr.h | 8 ++++ >>>>> 2 files changed, 98 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c >>>>> index 02ddbf9..1135d2b 100644 >>>>> --- a/hw/ppc/spapr_rtas.c >>>>> +++ b/hw/ppc/spapr_rtas.c >>>>> @@ -277,6 +277,91 @@ static void rtas_ibm_set_system_parameter(PowerPCCPU >>>>> *cpu, >>>>> rtas_st(rets, 0, ret); >>>>> } >>>>> >>>>> +static void rtas_ibm_nmi_register(PowerPCCPU *cpu, >>>>> + sPAPREnvironment *spapr, >>>>> + uint32_t token, uint32_t nargs, >>>>> + target_ulong args, >>>>> + uint32_t nret, target_ulong rets) >>>>> +{ >>>>> + int i; >>>>> + uint32_t branch_inst = 0x48000002; >>>>> + target_ulong guest_machine_check_addr; >>>>> + PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu); >>>>> + /* >>>>> + * Trampoline saves r3 in sprg2 and issues private hcall >>>>> + * to request qemu to build error log. QEMU builds the >>>>> + * error log, copies to rtas-blob and returns the address. >>>>> + * The initial 16 bytes in rtas-blob consists of saved srr0 >>>>> + * and srr1 which we restore and pass on the actual error >>>>> + * log address to OS handled mcachine check notification >>>>> + * routine >>>>> + */ >>>>> + uint32_t trampoline[] = { >>>>> + 0x7c7243a6, /* mtspr SPRN_SPRG2,r3 */ >>>>> + 0x38600000, /* li r3,0 */ >>>>> + /* 0xf004 is the KVMPPC_H_REPORT_ERR private HCALL */ >>>>> + 0x6063f004, /* ori r3,r3,f004 */ >>>>> + /* Issue H_CALL */ >>>>> + 0x44000022, /* sc 1 */ >>>> >>>> So up to here we're saving r3 in SPRG2 (how do we know that we can >>>> clobber it?) and call our special hypercall. >>>> >>>> But what does all the cruft below here do? >>> >>> The saved r3 in SPRG2 is consumed in KVMPPC_H_REPORT_ERR hcall, hence we >>> can clobber SPRG2 after hcall returns. I have included a comment in >>> patch 3/5 while building error log. I think better I add one here as well. >>> >>>> >>>>> + 0x7c9243a6, /* mtspr r4 sprg2 */ >>>> >>>> Apart from th fact that your order is wrong, this destroys the value of >>>> r3 that we saved above again. >>> >>> SPRG2 is saved inside hcall and hence we don't need SPRG2 further after >>> KVMPPC_H_REPORT_ERR hcall returns. >>> >>>> >>>>> + 0xe8830000, /* ld r4, 0(r3) */ >>>>> + 0x7c9a03a6, /* mtspr r4, srr0 */ >>>>> + 0xe8830008, /* ld r4, 8(r3) */ >>>>> + 0x7c9b03a6, /* mtspr r4, srr1 */ >>>> >>>> Can't we just set srr0 and srr1 directly? >>> >>> I checked for instructions in ISA which set srr0/1 directly given an >>> address, but could not find any such instructions. >> >> I mean from QEMU :). > > srr0 and srr1, which are properly set when 0x200 is invoked, are > clobbered when we return from KVMPPC_H_REPORT_ERR hcall. I think they > are modified before issuing rfid (I can see them getting clobbered from > QEMU monitor). However when we jump to OS registered machine check > routine srr0 and srr1 should reflect the value they had when 0x200 was > invoked. > > Hence srr0 and srr1 are saved in hcall and restored when we return from > hcall. Also we don't have enough scratch registers available to save > these before invoking hcall from 0x200. > > Or am I missing other ways to do this from QEMU?
If you just do cpu_synchronize_state() and then change env->spr[SPRN_SRR0/1] inside your hypercall handler that should also change the value when you return from the hcall. Alex