Re: [PATCH 13/19] KVM: PPC: Book3S HV: add a SYNC control for the XIVE native migration

["Cédric Le Goater" <clg@kaod.org>]

On 2/4/19 6:17 AM, David Gibson wrote:
> On Mon, Jan 07, 2019 at 07:43:25PM +0100, Cédric Le Goater wrote:
>> When migration of a VM is initiated, a first copy of the RAM is
>> transferred to the destination before the VM is stopped. At that time,
>> QEMU needs to perform a XIVE quiesce sequence to stop the flow of
>> event notifications and stabilize the EQs. The sources are masked and
>> the XIVE IC is synced with the KVM ioctl KVM_DEV_XIVE_GRP_SYNC.
>>
> 
> Don't you also need to make sure the guests queue pages are marked
> dirty here, in case they were already migrated?

I have added an extra KVM service to mark the EQ pages dirty. That 
might be overkill as it seems you are suggesting.

C. 
 
>> Signed-off-by: Cédric Le Goater <clg@kaod.org>
>> ---
>>  arch/powerpc/include/uapi/asm/kvm.h   |  1 +
>>  arch/powerpc/kvm/book3s_xive_native.c | 32 +++++++++++++++++++++++++++
>>  2 files changed, 33 insertions(+)
>>
>> diff --git a/arch/powerpc/include/uapi/asm/kvm.h b/arch/powerpc/include/uapi/asm/kvm.h
>> index 6fc9660c5aec..f3b859223b80 100644
>> --- a/arch/powerpc/include/uapi/asm/kvm.h
>> +++ b/arch/powerpc/include/uapi/asm/kvm.h
>> @@ -681,6 +681,7 @@ struct kvm_ppc_cpu_char {
>>  #define   KVM_DEV_XIVE_GET_TIMA_FD	2
>>  #define   KVM_DEV_XIVE_VC_BASE		3
>>  #define KVM_DEV_XIVE_GRP_SOURCES	2	/* 64-bit source attributes */
>> +#define KVM_DEV_XIVE_GRP_SYNC		3	/* 64-bit source attributes */
>>  
>>  /* Layout of 64-bit XIVE source attribute values */
>>  #define KVM_XIVE_LEVEL_SENSITIVE	(1ULL << 0)
>> diff --git a/arch/powerpc/kvm/book3s_xive_native.c b/arch/powerpc/kvm/book3s_xive_native.c
>> index 4ca75aade069..a8052867afc1 100644
>> --- a/arch/powerpc/kvm/book3s_xive_native.c
>> +++ b/arch/powerpc/kvm/book3s_xive_native.c
>> @@ -459,6 +459,35 @@ static int kvmppc_xive_native_set_source(struct kvmppc_xive *xive, long irq,
>>  	return 0;
>>  }
>>  
>> +static int kvmppc_xive_native_sync(struct kvmppc_xive *xive, long irq, u64 addr)
>> +{
>> +	struct kvmppc_xive_src_block *sb;
>> +	struct kvmppc_xive_irq_state *state;
>> +	struct xive_irq_data *xd;
>> +	u32 hw_num;
>> +	u16 src;
>> +
>> +	pr_devel("%s irq=0x%lx\n", __func__, irq);
>> +
>> +	sb = kvmppc_xive_find_source(xive, irq, &src);
>> +	if (!sb)
>> +		return -ENOENT;
>> +
>> +	state = &sb->irq_state[src];
>> +
>> +	if (!state->valid)
>> +		return -ENOENT;
>> +
>> +	arch_spin_lock(&sb->lock);
>> +
>> +	kvmppc_xive_select_irq(state, &hw_num, &xd);
>> +	xive_native_sync_source(hw_num);
>> +	xive_native_sync_queue(hw_num);
>> +
>> +	arch_spin_unlock(&sb->lock);
>> +	return 0;
>> +}
>> +
>>  static int kvmppc_xive_native_set_attr(struct kvm_device *dev,
>>  				       struct kvm_device_attr *attr)
>>  {
>> @@ -474,6 +503,8 @@ static int kvmppc_xive_native_set_attr(struct kvm_device *dev,
>>  	case KVM_DEV_XIVE_GRP_SOURCES:
>>  		return kvmppc_xive_native_set_source(xive, attr->attr,
>>  						     attr->addr);
>> +	case KVM_DEV_XIVE_GRP_SYNC:
>> +		return kvmppc_xive_native_sync(xive, attr->attr, attr->addr);
>>  	}
>>  	return -ENXIO;
>>  }
>> @@ -511,6 +542,7 @@ static int kvmppc_xive_native_has_attr(struct kvm_device *dev,
>>  		}
>>  		break;
>>  	case KVM_DEV_XIVE_GRP_SOURCES:
>> +	case KVM_DEV_XIVE_GRP_SYNC:
>>  		if (attr->attr >= KVMPPC_XIVE_FIRST_IRQ &&
>>  		    attr->attr < KVMPPC_XIVE_NR_IRQS)
>>  			return 0;
>