On Wed, Mar 13, 2019 at 12:48:57PM +0100, Cédric Le Goater wrote:
> On 2/25/19 3:53 AM, David Gibson wrote:
> > On Fri, Feb 22, 2019 at 12:28:33PM +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, but there is
> >> no guarantee that the EQ pages in which the event notification are
> >> queued have not been modified.
> >>
> >> To make sure migration will capture a consistent memory state, the
> >> XIVE device should perform a XIVE quiesce sequence to stop the flow of
> >> event notifications and stabilize the EQs. This is the purpose of the
> >> KVM_DEV_XIVE_EQ_SYNC control which will also marks the EQ pages dirty
> >> to force their transfer.
> >>
> >> Signed-off-by: Cédric Le Goater <clg@xxxxxxxx>
> >> ---
> >> arch/powerpc/include/uapi/asm/kvm.h | 1 +
> >> arch/powerpc/kvm/book3s_xive_native.c | 67 ++++++++++++++++++++++
> >> Documentation/virtual/kvm/devices/xive.txt | 29 ++++++++++
> >> 3 files changed, 97 insertions(+)
> >>
> >> diff --git a/arch/powerpc/include/uapi/asm/kvm.h b/arch/powerpc/include/uapi/asm/kvm.h
> >> index 289c504b7c1d..cd78ad1020fe 100644
> >> --- a/arch/powerpc/include/uapi/asm/kvm.h
> >> +++ b/arch/powerpc/include/uapi/asm/kvm.h
> >> @@ -678,6 +678,7 @@ struct kvm_ppc_cpu_char {
> >> /* POWER9 XIVE Native Interrupt Controller */
> >> #define KVM_DEV_XIVE_GRP_CTRL 1
> >> #define KVM_DEV_XIVE_RESET 1
> >> +#define KVM_DEV_XIVE_EQ_SYNC 2
> >> #define KVM_DEV_XIVE_GRP_SOURCE 2 /* 64-bit source attributes */
> >> #define KVM_DEV_XIVE_GRP_SOURCE_CONFIG 3 /* 64-bit source attributes */
> >> #define KVM_DEV_XIVE_GRP_EQ_CONFIG 4 /* 64-bit eq attributes */
> >> diff --git a/arch/powerpc/kvm/book3s_xive_native.c b/arch/powerpc/kvm/book3s_xive_native.c
> >> index dd2a9d411fe7..3debc876d5a0 100644
> >> --- a/arch/powerpc/kvm/book3s_xive_native.c
> >> +++ b/arch/powerpc/kvm/book3s_xive_native.c
> >> @@ -640,6 +640,70 @@ static int kvmppc_xive_reset(struct kvmppc_xive *xive)
> >> return 0;
> >> }
> >>
> >> +static void kvmppc_xive_native_sync_sources(struct kvmppc_xive_src_block *sb)
> >> +{
> >> + int j;
> >> +
> >> + for (j = 0; j < KVMPPC_XICS_IRQ_PER_ICS; j++) {
> >> + struct kvmppc_xive_irq_state *state = &sb->irq_state[j];
> >> + struct xive_irq_data *xd;
> >> + u32 hw_num;
> >> +
> >> + if (!state->valid)
> >> + continue;
> >> + if (state->act_priority == MASKED)
> >
> > Is this correct? If you masked an irq, then immediately did a sync,
> > couldn't there still be some of the irqs in flight? I thought the
> > reason we needed a sync was that masking and other such operations
> > _didn't_ implicitly synchronize.
>
> The struct kvmppc_xive_irq_state reflects the state of the EAS
> configuration and not the state of the source. The source is masked
> setting the PQ bits to '-Q', which is what is being done before calling
> the KVM_DEV_XIVE_EQ_SYNC control.
>
> If a source EAS is configured, OPAL syncs the XIVE IC of the source and
> the XIVE IC of the previous target if any.
>
> So I think we are fine.
Ok.
--
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
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