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From 148e9e80a3a430615b552075082fad22d007d851 Mon Sep 17 00:00:00 2001
From: David Gibson <>
Date: Wed, 6 Feb 2019 03:58:56 +0000
Subject: BZ1653590: Require at least 64kiB pages for downstream guests & hosts

RH-Author: David Gibson <>
Message-id: <>
Patchwork-id: 84246
O-Subject: [RHELAV-8.0/rhel qemu-kvm PATCH] BZ1653590: Require at least 64kiB pages for downstream guests & hosts
Bugzilla: 1653590
RH-Acked-by: Laurent Vivier <>
RH-Acked-by: Serhii Popovych <>
RH-Acked-by: Thomas Huth <>

Most current POWER guests require 64kiB page support, so that's the default
for the cap-hpt-max-pagesize option in qemu which limits available guest
page sizes.  We warn if the value is set smaller than that, but don't
outright fail upstream, because we need to allow for the possibility of
guest (and/or host) kernels configured for 4kiB page sizes.

Downstream, however, we simply don't support 4kiB pagesize configured
kernels in guest or host, so we can have qemu simply error out in this

Testing: Attempted to start a guest with cap-hpt-max-page-size=4k and verified
         it failed immediately with a qemu error

Signed-off-by: David Gibson <>
Signed-off-by: Danilo C. L. de Paula <>
 hw/ppc/spapr_caps.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c
index 481dfd2a27..805f38533e 100644
--- a/hw/ppc/spapr_caps.c
+++ b/hw/ppc/spapr_caps.c
@@ -351,12 +351,19 @@ void spapr_check_pagesize(SpaprMachineState *spapr, hwaddr pagesize,
 static void cap_hpt_maxpagesize_apply(SpaprMachineState *spapr,
                                       uint8_t val, Error **errp)
+#if 0 /* disabled for RHEL */
     if (val < 12) {
         error_setg(errp, "Require at least 4kiB hpt-max-page-size");
     } else if (val < 16) {
         warn_report("Many guests require at least 64kiB hpt-max-page-size");
+#else /* Only page sizes >=64kiB supported for RHEL */
+    if (val < 16) {
+        error_setg(errp, "Require at least 64kiB hpt-max-page-size");
+        return;
+    }
     spapr_check_pagesize(spapr, qemu_minrampagesize(), errp);