Re: [Qemu-devel] [PATCH v2 4/4] spapr: Introduce FWNMI KVM capability

[Aravinda Prasad <aravinda@linux.vnet.ibm.com>]

On Thursday 17 December 2015 09:32 AM, David Gibson wrote:
> On Wed, Dec 16, 2015 at 11:38:47AM +0530, Aravinda Prasad wrote:
>> Introduce a new KVM capability to control how KVM
>> behaves on machine check exception.
>>
>> Without this capability, KVM redirects machine check
>> exceptions to guest's 0x200 vector if the address in
>> error belongs to guest. With this capability KVM
>> causes a guest exit with NMI exit reason.
>>
>> This is required to avoid problem if a new kernel/KVM
>> is used with an old QEMU. As old QEMU might not
>> understand the new NMI exit type and treat it as a
>> fatal error, even though the guest could have actually
>> handled the error if the exception was delivered to
>> guest's 0x200 interrupt vector.
>>
>> PS: KVM_CAP_PPC_FWNMI is set to 121 as 119 and 120 are
>> used by KVM_CAP_GUEST_DEBUG_HW_BPS and KVM_CAP_GUEST_DEBUG_HW_WPS
>> in KVM code, but still not reflected in QEMU code.
> 
> The commit message seems to be written as if this were the kernel
> patch adding the capability there, rather than the qemu patch using
> it.
> 

I will reword it.

Regards,
Aravinda

>> Signed-off-by: Aravinda Prasad <aravinda@linux.vnet.ibm.com>
>> ---
>>  hw/ppc/spapr_rtas.c       |   17 +++++++++++++++++
>>  linux-headers/linux/kvm.h |    1 +
>>  target-ppc/kvm.c          |    2 ++
>>  3 files changed, 20 insertions(+)
>>
>> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
>> index 17c4672..53319da 100644
>> --- a/hw/ppc/spapr_rtas.c
>> +++ b/hw/ppc/spapr_rtas.c
>> @@ -38,6 +38,8 @@
>>  #include <libfdt.h>
>>  #include "hw/ppc/spapr_drc.h"
>>  
>> +extern int cap_fwnmi;
>> +
>>  /* #define DEBUG_SPAPR */
>>  
>>  #ifdef DEBUG_SPAPR
>> @@ -603,9 +605,24 @@ static void rtas_ibm_nmi_register(PowerPCCPU *cpu,
>>                                    target_ulong args,
>>                                    uint32_t nret, target_ulong rets)
>>  {
>> +    int ret;
>> +    CPUState *cs = CPU(cpu);
>> +
>> +    if (!cap_fwnmi) {
>> +        rtas_st(rets, 0, RTAS_OUT_NOT_SUPPORTED);
>> +        return;
>> +    }
>> +
>>      spapr->mc_in_progress = false;
>>      qemu_cond_init(&spapr->mc_delivery_cond);
>>      spapr->guest_machine_check_addr = rtas_ld(args, 1);
>> +
>> +    ret = kvm_vcpu_enable_cap(cs, KVM_CAP_PPC_FWNMI, 0);
>> +    if (ret < 0) {
>> +        rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
>> +        return;
>> +    }
>> +
>>      rtas_st(rets, 0, RTAS_OUT_SUCCESS);
>>  }
>>  
>> diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
>> index 683f713..2db1fba 100644
>> --- a/linux-headers/linux/kvm.h
>> +++ b/linux-headers/linux/kvm.h
>> @@ -819,6 +819,7 @@ struct kvm_ppc_smmu_info {
>>  #define KVM_CAP_DISABLE_QUIRKS 116
>>  #define KVM_CAP_X86_SMM 117
>>  #define KVM_CAP_MULTI_ADDRESS_SPACE 118
>> +#define KVM_CAP_PPC_FWNMI 121
>>  
>>  #ifdef KVM_CAP_IRQ_ROUTING
>>  
>> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
>> index 2bbb46d..5339c04 100644
>> --- a/target-ppc/kvm.c
>> +++ b/target-ppc/kvm.c
>> @@ -74,6 +74,7 @@ static int cap_ppc_watchdog;
>>  static int cap_papr;
>>  static int cap_htab_fd;
>>  static int cap_fixup_hcalls;
>> +int cap_fwnmi;
>>  
>>  static uint32_t debug_inst_opcode;
>>  
>> @@ -116,6 +117,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>>       * only activated after this by kvmppc_set_papr() */
>>      cap_htab_fd = kvm_check_extension(s, KVM_CAP_PPC_HTAB_FD);
>>      cap_fixup_hcalls = kvm_check_extension(s, KVM_CAP_PPC_FIXUP_HCALL);
>> +    cap_fwnmi = kvm_check_extension(s, KVM_CAP_PPC_FWNMI);
>>  
>>      if (!cap_interrupt_level) {
>>          fprintf(stderr, "KVM: Couldn't find level irq capability. Expect the "
>>
> 

-- 
Regards,
Aravinda