Re: [RFC PATCH] spapr/xive: Allocate vCPU IPIs from local context

[Greg Kurz <groug@kaod.org>]

On Fri, 1 Oct 2021 11:59:45 +0200
Cédric Le Goater <clg@kaod.org> wrote:

> >>> Maybe it would be simpler to call xive_source_is_initialized() instead of
> >>> xive_eas_is_valid() in cases like this, e.g. hcall code since it is shared
> >>> between emulation and KVM ?
> >>
> >> Yes but we need a better check than :
> >>
> >>       if (lisn < SPAPR_XIRQ_BASE) {
> >>           return !!xive_get_field64(EAS_END_INDEX, xive->eat[lisn].w);
> >>       }
> >>
> >> This is more an heuristic than a precise test on the "validity" of
> >> a source at the KVM level.
> >>
> > 
> > I guess we should be able to get kvmppc_xive_irq_state::valid from
> > KVM by making the KVM_DEV_XIVE_GRP_SOURCE attribute readable. Would
> > that be enough ?
> 
> A bit slow may be. Or an extra bit in the XiveSource 'status' field
> to reflect KVM initialization.
> 
> C.
> 

Something like this ?

diff --git a/hw/intc/spapr_xive_kvm.c b/hw/intc/spapr_xive_kvm.c
index 42f72b68fc00..6eba58b0ff10 100644
--- a/hw/intc/spapr_xive_kvm.c
+++ b/hw/intc/spapr_xive_kvm.c
@@ -232,6 +232,7 @@ int kvmppc_xive_source_reset_one(XiveSource *xsrc, int srcno, Error **errp)
 {
     SpaprXive *xive = SPAPR_XIVE(xsrc->xive);
     uint64_t state = 0;
+    int ret;
 
     assert(xive->fd != -1);
 
@@ -242,8 +243,15 @@ int kvmppc_xive_source_reset_one(XiveSource *xsrc, int srcno, Error **errp)
         }
     }
 
-    return kvm_device_access(xive->fd, KVM_DEV_XIVE_GRP_SOURCE, srcno, &state,
-                             true, errp);
+    ret = kvm_device_access(xive->fd, KVM_DEV_XIVE_GRP_SOURCE, srcno, &state,
+                            true, errp);
+    if (ret < 0) {
+        return ret;
+    }
+
+    xsrc->status[srcno] |= XIVE_STATUS_KVM;
+
+    return 0;
 }
 
 static int kvmppc_xive_source_reset(XiveSource *xsrc, Error **errp)
diff --git a/include/hw/ppc/xive.h b/include/hw/ppc/xive.h
index 445eccfe6b73..d85520beb64a 100644
--- a/include/hw/ppc/xive.h
+++ b/include/hw/ppc/xive.h
@@ -252,6 +252,7 @@ static inline hwaddr xive_source_esb_mgmt(XiveSource *xsrc, int srcno)
  * When doing an EOI, the Q bit will indicate if the interrupt
  * needs to be re-triggered.
  */
+#define XIVE_STATUS_KVM       0x8  /* Set when initialized in KVM */
 #define XIVE_STATUS_ASSERTED  0x4  /* Extra bit for LSI */
 #define XIVE_ESB_VAL_P        0x2
 #define XIVE_ESB_VAL_Q        0x1