ppc/xive: Always recompute the PIPR when pushing an OS context

The Post Interrupt Priority Register (PIPR) is not restored like the
other OS-context related fields of the TIMA when pushing an OS context
on the CPU. It's not needed because it can be calculated from the
Interrupt Pending Buffer (IPB), which is saved and restored. The PIPR
must therefore always be recomputed when pushing an OS context.

This patch fixes a path on P9 and P10 where it was not done. If there
was a pending interrupt when the OS context was pulled, the IPB was
saved correctly. When pushing back the context, the code in
xive_tctx_need_resend() was checking for a interrupt raised while the
context was not on the CPU, saved in the NVT. If one was found, then
it was merged with the saved IPB and the PIPR updated and everything
was fine. However, if there was no interrupt found in the NVT, then
xive_tctx_ipb_update() was not being called and the PIPR was not
updated. This patch fixes it by always calling xive_tctx_ipb_update().

Note that on P10 (xive2.c) and because of the above, there's no longer
any need to check the CPPR value so it can go away.

Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com>
Message-Id: <20220429071620.177142-2-fbarrat@linux.ibm.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>

2 files changed, 17 insertions, 10 deletions

diff --git a/hw/intc/xive.c b/hw/intc/xive.c
index b8e4c72..c729f6a 100644
--- a/hw/intc/xive.c
+++ b/hw/intc/xive.c
@@ -413,10 +413,15 @@ static void xive_tctx_need_resend(XiveRouter *xrtr, XiveTCTX *tctx,
         /* 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);
     }
+    /*
+     * Always call xive_tctx_ipb_update(). Even if there were no
+     * escalation triggered, there could be a pending interrupt which
+     * was saved when the context was pulled and that we need to take
+     * into account by recalculating the PIPR (which is not
+     * saved/restored).
+     */
+    xive_tctx_ipb_update(tctx, TM_QW1_OS, ipb);
 }
 
 /*
diff --git a/hw/intc/xive2.c b/hw/intc/xive2.c
index 3aff42a..400fd70 100644
--- a/hw/intc/xive2.c
+++ b/hw/intc/xive2.c
@@ -316,7 +316,6 @@ static void xive2_tctx_need_resend(Xive2Router *xrtr, XiveTCTX *tctx,
 {
     Xive2Nvp nvp;
     uint8_t ipb;
-    uint8_t cppr = 0;
 
     /*
      * Grab the associated thread interrupt context registers in the
@@ -337,7 +336,7 @@ static void xive2_tctx_need_resend(Xive2Router *xrtr, XiveTCTX *tctx,
     /* Automatically restore thread context registers */
     if (xive2_router_get_config(xrtr) & XIVE2_VP_SAVE_RESTORE &&
         do_restore) {
-        cppr = xive2_tctx_restore_os_ctx(xrtr, tctx, nvp_blk, nvp_idx, &nvp);
+        xive2_tctx_restore_os_ctx(xrtr, tctx, nvp_blk, nvp_idx, &nvp);
     }
 
     ipb = xive_get_field32(NVP2_W2_IPB, nvp.w2);
@@ -345,11 +344,14 @@ static void xive2_tctx_need_resend(Xive2Router *xrtr, XiveTCTX *tctx,
         nvp.w2 = xive_set_field32(NVP2_W2_IPB, nvp.w2, 0);
         xive2_router_write_nvp(xrtr, nvp_blk, nvp_idx, &nvp, 2);
     }
-
-    /* An IPB or CPPR change can trigger a resend */
-    if (ipb || cppr) {
-        xive_tctx_ipb_update(tctx, TM_QW1_OS, ipb);
-    }
+    /*
+     * Always call xive_tctx_ipb_update(). Even if there were no
+     * escalation triggered, there could be a pending interrupt which
+     * was saved when the context was pulled and that we need to take
+     * into account by recalculating the PIPR (which is not
+     * saved/restored).
+     */
+    xive_tctx_ipb_update(tctx, TM_QW1_OS, ipb);
 }
 
 /*