On 05.11.14 11:37, Aravinda Prasad wrote:
>
>
> On Wednesday 05 November 2014 02:02 PM, Alexander Graf wrote:
>>
>>
>> On 05.11.14 08:13, 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.
>>>
>>> This patch also handles the cases when multi-processors
>>> experience machine check at or about the same time.
>>> As per PAPR, subsequent processors serialize waiting
>>> for the first processor to issue the ibm,nmi-interlock call.
>>> The second processor retries if the first processor which
>>> received a machine check is still reading the error log
>>> and is yet to issue ibm,nmi-interlock call.
>>>
>>> Signed-off-by: Aravinda Prasad <aravi...@linux.vnet.ibm.com>
>>> ---
>>> hw/ppc/spapr_hcall.c | 16 +++++++
>>> hw/ppc/spapr_rtas.c | 93
>>> +++++++++++++++++++++++++++++++++++++++
>>> include/hw/ppc/spapr.h | 17 +++++++
>>> pc-bios/spapr-rtas/spapr-rtas.S | 38 ++++++++++++++++
>>> 4 files changed, 163 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
>>> index 8f16160..eceb5e5 100644
>>> --- a/hw/ppc/spapr_hcall.c
>>> +++ b/hw/ppc/spapr_hcall.c
>>> @@ -97,6 +97,9 @@ struct rtas_mc_log {
>>> struct rtas_error_log err_log;
>>> };
>>>
>>> +/* Whether machine check handling is in progress by any CPU */
>>> +bool mc_in_progress;
>>> +
>>> static void do_spr_sync(void *arg)
>>> {
>>> struct SPRSyncState *s = arg;
>>> @@ -678,6 +681,19 @@ static target_ulong h_report_mc_err(PowerPCCPU *cpu,
>>> sPAPREnvironment *spapr,
>>> cpu_synchronize_state(CPU(ppc_env_get_cpu(env)));
>>>
>>> /*
>>> + * Only one VCPU can process machine check NMI at a time. Hence
>>> + * set the lock mc_in_progress. Once the VCPU finishes processing
>>> + * NMI, it executes ibm,nmi-interlock and mc_in_progress is unset
>>> + * in ibm,nmi-interlock handler. Meanwhile if other VCPUs encounter
>>> + * NMI we return 0 asking the VCPU to retry h_report_mc_err
>>> + */
>>> + if (mc_in_progress == 1) {
>>
>> Please don't depend on bools being numbers. Use true / false. For if()s,
>> just don't use == at all - it makes it more readable.
>
> ok
>
>>
>>> + return 0;
>>> + }
>>> +
>>> + mc_in_progress = 1;
>>> +
>>> + /*
>>> * We save the original r3 register in SPRG2 in 0x200 vector,
>>> * which is patched during call to ibm.nmi-register. Original
>>> * r3 is required to be included in error log
>>> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
>>> index 2ec2a8e..71c7662 100644
>>> --- a/hw/ppc/spapr_rtas.c
>>> +++ b/hw/ppc/spapr_rtas.c
>>> @@ -36,6 +36,9 @@
>>>
>>> #include <libfdt.h>
>>>
>>> +#define BRANCH_INST_MASK 0xFC000000
>>> +extern bool mc_in_progress;
>>
>> Please put this into the spapr struct.
>
> ok
>
>>
>>> +
>>> static void rtas_display_character(PowerPCCPU *cpu, sPAPREnvironment
>>> *spapr,
>>> uint32_t token, uint32_t nargs,
>>> target_ulong args,
>>> @@ -290,6 +293,90 @@ static void rtas_ibm_os_term(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 ori_inst = 0x60630000;
>>> + uint32_t branch_inst = 0x48000002;
>>> + target_ulong guest_machine_check_addr;
>>> + uint32_t trampoline[TRAMPOLINE_INSTS];
>>> + int total_inst = sizeof(trampoline) / sizeof(uint32_t);
>>
>> ARRAY_SIZE(trampoline), though I don't quite understand why you need a
>> variable that contains the same value as a constant (TRAMPOLINE_INSTS).
>>
>> But since you're moving all of those bits into variable fields on the
>> rtas blob itself as we discussed in the last version, I guess this code
>> will go away anyways ;).
>
> I think we still need this. We need to patch the KVMPPC_H_REPORT_MC_ERR
> number and branch address in the trampoline and also, depending on
> whether the guest running in LE/BE we may need to flip the bits in the
> trampoline before copying it to 0x200 machine check vector.
>
> As rtas-blob is part of the guest memory I do not want to patch these in
> rtas-blob, hence I copy the trampoline from the rtas-blob to an array,
> modify accordingly and then move it to 0x200 machine check vector.
Yes, you will still need the array. But the array should be dynamically
sized based on spapr->rtas_info->fwnmi_size which you extract from the
blob on load.
That way you wouldn't need the "total_inst" variable anymore ;).
>
>>
>>> + PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu);
>>> +
>>> + /* Store the system reset and machine check address */
>>> + guest_machine_check_addr = rtas_ld(args, 1);
>>
>> Load or Store? I don't find the comment particularly useful either ;).
>
> will reword it or may delete it.
>
>>
>>> +
>>> + /*
>>> + * Read the trampoline instructions from RTAS Blob and patch
>>> + * the KVMPPC_H_REPORT_MC_ERR hcall number and the guest
>>> + * machine check address before copying to 0x200 vector
>>> + */
>>> + cpu_physical_memory_read(spapr->rtas_addr + RTAS_TRAMPOLINE_OFFSET,
>>> + trampoline, sizeof(trampoline));
>>> +
>>> + /* Safety Check */
>>
>> Same for this comment.
>
> we have only 0x100 bytes that can be copied at 0x200. If the trampoline
> size exceeds then the next interrupt vector code is overwritten. Hence a
> safety check during compile time to make sure trampoline is within 0x100
> bytes.
I think the check is fine, the comment is just redundant with
QEMU_BUILD_BUG_ON. Either be more verbose in the comment or remove it
;). But something a la
/* check for failure */
BUG_ON(foo);
is useless redundancy, because everyone already knows that BUG_ON checks
for failure.
The interesting bit is the why. Also, as a general rule of thumb, if you
need a comment explaining the "what" of what you're doing, your function
and/or variable names are probably not well chosen ;). But I don't think
this is a problem here.
Thanks for the patches btw :)
Alex
