Subject: Re: [PATCH 14/19] KVM: PPC: Book3S HV: add a control to make the XIVE EQ pages dirty

From: David Gibson <[email-masked]>
Date: Mon, 4 Feb 2019 16:18:34 +1100

On Mon, Jan 07, 2019 at 07:43:26PM +0100, Cédric Le Goater wrote:
> When the VM is stopped in a migration sequence, the sources are masked
> and the XIVE IC is synced to stabilize the EQs. When done, the KVM
> ioctl KVM_DEV_XIVE_SAVE_EQ_PAGES is called to mark dirty the EQ pages.
> 
> The migration can then transfer the remaining dirty pages to the
> destination and start collecting the state of the devices.

Is there a reason to make this a separate step from the SYNC
operation?

> 
> Signed-off-by: Cédric Le Goater <[email-masked]>
> ---
>  arch/powerpc/include/uapi/asm/kvm.h   |  1 +
>  arch/powerpc/kvm/book3s_xive_native.c | 40 +++++++++++++++++++++++++++
>  2 files changed, 41 insertions(+)
> 
> diff --git a/arch/powerpc/include/uapi/asm/kvm.h b/arch/powerpc/include/uapi/asm/kvm.h
> index f3b859223b80..1a8740629acf 100644
> --- a/arch/powerpc/include/uapi/asm/kvm.h
> +++ b/arch/powerpc/include/uapi/asm/kvm.h
> @@ -680,6 +680,7 @@ struct kvm_ppc_cpu_char {
>  #define   KVM_DEV_XIVE_GET_ESB_FD	1
>  #define   KVM_DEV_XIVE_GET_TIMA_FD	2
>  #define   KVM_DEV_XIVE_VC_BASE		3
> +#define   KVM_DEV_XIVE_SAVE_EQ_PAGES	4
>  #define KVM_DEV_XIVE_GRP_SOURCES	2	/* 64-bit source attributes */
>  #define KVM_DEV_XIVE_GRP_SYNC		3	/* 64-bit source attributes */
>  
> diff --git a/arch/powerpc/kvm/book3s_xive_native.c b/arch/powerpc/kvm/book3s_xive_native.c
> index a8052867afc1..f2de1bcf3b35 100644
> --- a/arch/powerpc/kvm/book3s_xive_native.c
> +++ b/arch/powerpc/kvm/book3s_xive_native.c
> @@ -373,6 +373,43 @@ static int kvmppc_xive_native_get_tima_fd(struct kvmppc_xive *xive, u64 addr)
>  	return put_user(ret, ubufp);
>  }
>  
> +static int kvmppc_xive_native_vcpu_save_eq_pages(struct kvm_vcpu *vcpu)
> +{
> +	struct kvmppc_xive_vcpu *xc = vcpu->arch.xive_vcpu;
> +	unsigned int prio;
> +
> +	if (!xc)
> +		return -ENOENT;
> +
> +	for (prio = 0; prio < KVMPPC_XIVE_Q_COUNT; prio++) {
> +		struct xive_q *q = &xc->queues[prio];
> +
> +		if (!q->qpage)
> +			continue;
> +
> +		/* Mark EQ page dirty for migration */
> +		mark_page_dirty(vcpu->kvm, gpa_to_gfn(q->guest_qpage));
> +	}
> +	return 0;
> +}
> +
> +static int kvmppc_xive_native_save_eq_pages(struct kvmppc_xive *xive)
> +{
> +	struct kvm *kvm = xive->kvm;
> +	struct kvm_vcpu *vcpu;
> +	unsigned int i;
> +
> +	pr_devel("%s\n", __func__);
> +
> +	mutex_lock(&kvm->lock);
> +	kvm_for_each_vcpu(i, vcpu, kvm) {
> +		kvmppc_xive_native_vcpu_save_eq_pages(vcpu);
> +	}
> +	mutex_unlock(&kvm->lock);
> +
> +	return 0;
> +}
> +
>  static int xive_native_validate_queue_size(u32 qsize)
>  {
>  	switch (qsize) {
> @@ -498,6 +535,8 @@ static int kvmppc_xive_native_set_attr(struct kvm_device *dev,
>  		switch (attr->attr) {
>  		case KVM_DEV_XIVE_VC_BASE:
>  			return kvmppc_xive_native_set_vc_base(xive, attr->addr);
> +		case KVM_DEV_XIVE_SAVE_EQ_PAGES:
> +			return kvmppc_xive_native_save_eq_pages(xive);
>  		}
>  		break;
>  	case KVM_DEV_XIVE_GRP_SOURCES:
> @@ -538,6 +577,7 @@ static int kvmppc_xive_native_has_attr(struct kvm_device *dev,
>  		case KVM_DEV_XIVE_GET_ESB_FD:
>  		case KVM_DEV_XIVE_GET_TIMA_FD:
>  		case KVM_DEV_XIVE_VC_BASE:
> +		case KVM_DEV_XIVE_SAVE_EQ_PAGES:
>  			return 0;
>  		}
>  		break;

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson