[PATCH v6 17/20] ppc/xive: Synthesize interrupt from the saved IPB in the NVT

["Cédric Le Goater" <clg@kaod.org>]

When a vCPU is dispatched on a HW thread, its context is pushed in the
thread registers and it is activated by setting the VO bit in the CAM
line word2. The HW grabs the associated NVT, pulls the IPB bits and
merges them with the IPB of the new context. If interrupts were missed
while the vCPU was not dispatched, these are synthesized in this
sequence.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
---
 hw/intc/xive.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/hw/intc/xive.c b/hw/intc/xive.c
index 7047e45daca1..e022bb7afd28 100644
--- a/hw/intc/xive.c
+++ b/hw/intc/xive.c
@@ -393,6 +393,57 @@ static uint64_t xive_tm_pull_os_ctx(XivePresenter *xptr, XiveTCTX *tctx,
     return qw1w2;
 }
 
+static void xive_tctx_need_resend(XiveRouter *xrtr, XiveTCTX *tctx,
+                                  uint8_t nvt_blk, uint32_t nvt_idx)
+{
+    XiveNVT nvt;
+    uint8_t ipb;
+
+    /*
+     * Grab the associated NVT to pull the pending bits, and merge
+     * them with the IPB of the thread interrupt context registers
+     */
+    if (xive_router_get_nvt(xrtr, nvt_blk, nvt_idx, &nvt)) {
+        qemu_log_mask(LOG_GUEST_ERROR, "XIVE: invalid NVT %x/%x\n",
+                          nvt_blk, nvt_idx);
+        return;
+    }
+
+    ipb = xive_get_field32(NVT_W4_IPB, nvt.w4);
+
+    if (ipb) {
+        /* Reset the NVT value */
+        nvt.w4 = xive_set_field32(NVT_W4_IPB, nvt.w4, 0);
+        xive_router_write_nvt(xrtr, nvt_blk, nvt_idx, &nvt, 4);
+
+        /* Merge in current context */
+        xive_tctx_ipb_update(tctx, TM_QW1_OS, ipb);
+    }
+}
+
+/*
+ * Updating the OS CAM line can trigger a resend of interrupt
+ */
+static void xive_tm_push_os_ctx(XivePresenter *xptr, XiveTCTX *tctx,
+                                hwaddr offset, uint64_t value, unsigned size)
+{
+    uint32_t cam = value;
+    uint32_t qw1w2 = cpu_to_be32(cam);
+    uint8_t nvt_blk;
+    uint32_t nvt_idx;
+    bool vo;
+
+    xive_os_cam_decode(cam, &nvt_blk, &nvt_idx, &vo);
+
+    /* First update the registers */
+    xive_tctx_set_os_cam(tctx, qw1w2);
+
+    /* Check the interrupt pending bits */
+    if (vo) {
+        xive_tctx_need_resend(XIVE_ROUTER(xptr), tctx, nvt_blk, nvt_idx);
+    }
+}
+
 /*
  * Define a mapping of "special" operations depending on the TIMA page
  * offset and the size of the operation.
@@ -414,6 +465,7 @@ static const XiveTmOp xive_tm_operations[] = {
      * effects
      */
     { XIVE_TM_OS_PAGE, TM_QW1_OS + TM_CPPR,   1, xive_tm_set_os_cppr, NULL },
+    { XIVE_TM_HV_PAGE, TM_QW1_OS + TM_WORD2,     4, xive_tm_push_os_ctx, NULL },
     { XIVE_TM_HV_PAGE, TM_QW3_HV_PHYS + TM_CPPR, 1, xive_tm_set_hv_cppr, NULL },
     { XIVE_TM_HV_PAGE, TM_QW3_HV_PHYS + TM_WORD2, 1, xive_tm_vt_push, NULL },
     { XIVE_TM_HV_PAGE, TM_QW3_HV_PHYS + TM_WORD2, 1, NULL, xive_tm_vt_poll },
-- 
2.21.0