Re: [Qemu-ppc] [PATCH v2 04/13] spapr/xive: add state synchronization with KVM

[Cédric Le Goater]

On 3/14/19 3:10 AM, David Gibson wrote:
> On Mon, Mar 11, 2019 at 09:41:12PM +0100, Cédric Le Goater wrote:
>> On 2/26/19 1:01 AM, David Gibson wrote:
>>> On Fri, Feb 22, 2019 at 02:13:13PM +0100, Cédric Le Goater wrote:
>>>> This extends the KVM XIVE device backend with 'synchronize_state'
>>>> methods used to retrieve the state from KVM. The HW state of the
>>>> sources, the KVM device and the thread interrupt contexts are
>>>> collected for the monitor usage and also migration.
>>>>
>>>> These get operations rely on their KVM counterpart in the host kernel
>>>> which acts as a proxy for OPAL, the host firmware. The set operations
>>>> will be added for migration support later.
>>>>
>>>> Signed-off-by: Cédric Le Goater <address@hidden>
>>>> ---
>>>>  include/hw/ppc/spapr_xive.h |  8 ++++
>>>>  include/hw/ppc/xive.h       |  1 +
>>>>  hw/intc/spapr_xive.c        | 17 ++++---
>>>>  hw/intc/spapr_xive_kvm.c    | 89 +++++++++++++++++++++++++++++++++++++
>>>>  hw/intc/xive.c              | 10 +++++
>>>>  5 files changed, 118 insertions(+), 7 deletions(-)
>>>>
>>>> diff --git a/include/hw/ppc/spapr_xive.h b/include/hw/ppc/spapr_xive.h
>>>> index 749c6cbc2c56..ebd65e7fe36b 100644
>>>> --- a/include/hw/ppc/spapr_xive.h
>>>> +++ b/include/hw/ppc/spapr_xive.h
>>>> @@ -44,6 +44,13 @@ typedef struct sPAPRXive {
>>>>      void          *tm_mmap;
>>>>  } sPAPRXive;
>>>>  
>>>> +/*
>>>> + * The sPAPR machine has a unique XIVE IC device. Assign a fixed value
>>>> + * to the controller block id value. It can nevertheless be changed
>>>> + * for testing purpose.
>>>> + */
>>>> +#define SPAPR_XIVE_BLOCK_ID 0x0
>>>> +
>>>>  bool spapr_xive_irq_claim(sPAPRXive *xive, uint32_t lisn, bool lsi);
>>>>  bool spapr_xive_irq_free(sPAPRXive *xive, uint32_t lisn);
>>>>  void spapr_xive_pic_print_info(sPAPRXive *xive, Monitor *mon);
>>>> @@ -74,5 +81,6 @@ void kvmppc_xive_set_queue_config(sPAPRXive *xive, 
>>>> uint8_t end_blk,
>>>>  void kvmppc_xive_get_queue_config(sPAPRXive *xive, uint8_t end_blk,
>>>>                                   uint32_t end_idx, XiveEND *end,
>>>>                                   Error **errp);
>>>> +void kvmppc_xive_synchronize_state(sPAPRXive *xive, Error **errp);
>>>>  
>>>>  #endif /* PPC_SPAPR_XIVE_H */
>>>> diff --git a/include/hw/ppc/xive.h b/include/hw/ppc/xive.h
>>>> index 061d43fea24d..f3766fd881a2 100644
>>>> --- a/include/hw/ppc/xive.h
>>>> +++ b/include/hw/ppc/xive.h
>>>> @@ -431,5 +431,6 @@ void kvmppc_xive_source_reset_one(XiveSource *xsrc, 
>>>> int srcno, Error **errp);
>>>>  void kvmppc_xive_source_reset(XiveSource *xsrc, Error **errp);
>>>>  void kvmppc_xive_source_set_irq(void *opaque, int srcno, int val);
>>>>  void kvmppc_xive_cpu_connect(XiveTCTX *tctx, Error **errp);
>>>> +void kvmppc_xive_cpu_synchronize_state(XiveTCTX *tctx, Error **errp);
>>>>  
>>>>  #endif /* PPC_XIVE_H */
>>>> diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
>>>> index 3db24391e31c..9f07567f4d78 100644
>>>> --- a/hw/intc/spapr_xive.c
>>>> +++ b/hw/intc/spapr_xive.c
>>>> @@ -40,13 +40,6 @@
>>>>  
>>>>  #define SPAPR_XIVE_NVT_BASE 0x400
>>>>  
>>>> -/*
>>>> - * The sPAPR machine has a unique XIVE IC device. Assign a fixed value
>>>> - * to the controller block id value. It can nevertheless be changed
>>>> - * for testing purpose.
>>>> - */
>>>> -#define SPAPR_XIVE_BLOCK_ID 0x0
>>>> -
>>>>  /*
>>>>   * sPAPR NVT and END indexing helpers
>>>>   */
>>>> @@ -153,6 +146,16 @@ void spapr_xive_pic_print_info(sPAPRXive *xive, 
>>>> Monitor *mon)
>>>>      XiveSource *xsrc = &xive->source;
>>>>      int i;
>>>>  
>>>> +    if (kvm_irqchip_in_kernel()) {
>>>> +        Error *local_err = NULL;
>>>> +
>>>> +        kvmppc_xive_synchronize_state(xive, &local_err);
>>>> +        if (local_err) {
>>>> +            error_report_err(local_err);
>>>> +            return;
>>>> +        }
>>>> +    }
>>>> +
>>>>      monitor_printf(mon, "  LSIN         PQ    EISN     CPU/PRIO EQ\n");
>>>>  
>>>>      for (i = 0; i < xive->nr_irqs; i++) {
>>>> diff --git a/hw/intc/spapr_xive_kvm.c b/hw/intc/spapr_xive_kvm.c
>>>> index 6b50451b4f85..4b1ffb9835f9 100644
>>>> --- a/hw/intc/spapr_xive_kvm.c
>>>> +++ b/hw/intc/spapr_xive_kvm.c
>>>> @@ -60,6 +60,57 @@ static void kvm_cpu_enable(CPUState *cs)
>>>>  /*
>>>>   * XIVE Thread Interrupt Management context (KVM)
>>>>   */
>>>> +static void kvmppc_xive_cpu_get_state(XiveTCTX *tctx, Error **errp)
>>>> +{
>>>> +    uint64_t state[4] = { 0 };
>>>> +    int ret;
>>>> +
>>>> +    ret = kvm_get_one_reg(tctx->cs, KVM_REG_PPC_NVT_STATE, state);
>>>> +    if (ret != 0) {
>>>> +        error_setg_errno(errp, errno,
>>>> +                         "XIVE: could not capture KVM state of CPU %ld",
>>>> +                         kvm_arch_vcpu_id(tctx->cs));
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    /* word0 and word1 of the OS ring. */
>>>> +    *((uint64_t *) &tctx->regs[TM_QW1_OS]) = state[0];
>>>> +
>>>> +    /*
>>>> +     * KVM also returns word2 containing the OS CAM line which is
>>>> +     * interesting to print out in the QEMU monitor.
>>>> +     */
>>>> +    *((uint64_t *) &tctx->regs[TM_QW1_OS + TM_WORD2]) = state[1];
>>>
>>> As mentioned elsewhere, it is interesting for debugging, but doesn't
>>> seem to really match the guest visible CAM state, 
>>
>> The guest is not allowed to see these registers in the TIMA OS page 
> 
> Ah.. right.  IIRC, roughly speaking the first doubleword in each ring
> belongs to that level, but the second doubleword belongs to the right
> above (since that's what manages the scheduling of what's in this
> ring).
> 
> Makes it a big bogus to carry that as migrated state then.
> 
>> and we are not violating the XIVE architecture. That is where the 
>> CAM value belong in HW. The exact same place. I was even thinking 
>> to propagate the POOL value which could be useful for nested.
>>
>>> so I'm not convinced it's a good idea to put it into the regs[] 
>>> structure.
>>
>> I understand it is problematic in case of a KVM->QEMU migration 
>> because we need to force a XiveTCTX reset to update the registers 
>> with the QEMU CAM line which has been overridden with the KVM CAM 
>> line. 
>>
>> Another solution could be to add a 'nvt_base' property to SpaprXive 
>> and a KVM control to get its value (xive->vp_base in the KVM XIVE 
>> device). It would be migrated and used by the QEMU XIVE device 
>> after migration. 
>>  
>>>> +}
>>>> +
>>>> +typedef struct {
>>>> +    XiveTCTX *tctx;
>>>> +    Error *err;
>>>> +} XiveCpuGetState;
>>>> +
>>>> +static void kvmppc_xive_cpu_do_synchronize_state(CPUState *cpu,
>>>> +                                                 run_on_cpu_data arg)
>>>> +{
>>>> +    XiveCpuGetState *s = arg.host_ptr;
>>>> +
>>>> +    kvmppc_xive_cpu_get_state(s->tctx, &s->err);
>>>> +}
>>>> +
>>>> +void kvmppc_xive_cpu_synchronize_state(XiveTCTX *tctx, Error **errp)
>>>> +{
>>>> +    XiveCpuGetState s = {
>>>> +        .tctx = tctx,
>>>> +        .err = NULL,
>>>> +    };
>>>> +
>>>> +    run_on_cpu(tctx->cs, kvmppc_xive_cpu_do_synchronize_state,
>>>> +               RUN_ON_CPU_HOST_PTR(&s));
>>>
>>> Why does this need a run_on_cpu() ?  The KVM call which is getting the
>>> actual info takes a cpu parameter.
>>
>> Don't we need to kick the vCPU ?
> 
> Um.. you tell me?  

we do need to kick the vCPU. 

> If it's not safe to call on a vcpu other than one
> owned by the calling thread, I'm not sure if the cpu parameter makes
> sense.

That's the typedef we need to use with run_on_cpu() :

        typedef void (*run_on_cpu_func)(CPUState *cpu, run_on_cpu_data data);

I am not sure where you are getting at with this cpu parameter.

C.