From 19ab0de29b4a853622fbccccf957f6a2c44466f3 Mon Sep 17 00:00:00 2001

From: Laurent Vivier <lvivier@redhat.com>

Date: Tue, 19 Dec 2017 10:42:36 +0100

Subject: [PATCH 01/42] spapr: don't initialize PATB entry if max-cpu-compat <

 power9

RH-Author: Laurent Vivier <lvivier@redhat.com>

Message-id: <20171219104236.22556-1-lvivier@redhat.com>

Patchwork-id: 78413

O-Subject: [RHV7.5 qemu-kvm-rhev PATCH] spapr: don't initialize PATB entry if max-cpu-compat < power9

Bugzilla: 1525866

RH-Acked-by: David Gibson <dgibson@redhat.com>

RH-Acked-by: Thomas Huth <thuth@redhat.com>

RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com>

BZ:     https://bugzilla.redhat.com/show_bug.cgi?id=1525866

BREW:   https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=14815605

        s390x build is broken (binutils is missing), build only the others

Tested: I tested this patch with upstream QEMU.

        As it is difficult to have a P9 host in beaker to check migration

        to P8 host, I didn't re-test it with downstream build

        (but I have asked QE to do)

if KVM is enabled and KVM capabilities MMU radix is available,

the partition table entry (patb_entry) for the radix mode is

initialized by default in ppc_spapr_reset().

It's a problem if we want to migrate the guest to a POWER8 host

while the kernel is not started to set the value to the one

expected for a POWER8 CPU.

The "-machine max-cpu-compat=power8" should allow to migrate

a POWER9 KVM host to a POWER8 KVM host, but because patb_entry

is set, the destination QEMU tries to enable radix mode on the

POWER8 host. This fails and cancels the migration:

    Process table config unsupported by the host

    error while loading state for instance 0x0 of device 'spapr'

    load of migration failed: Invalid argument

This patch doesn't set the PATB entry if the user provides

a CPU compatibility mode that doesn't support radix mode.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

(cherry picked from commit 1481fe5fcfeb7fcf3c1ebb9d8c0432e3e0188ccf)

Signed-off-by: Laurent Vivier <lvivier@redhat.com>

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 hw/ppc/spapr.c | 6 ++++--

 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c

index af7a3bb..d320b6c 100644

--- a/hw/ppc/spapr.c

+++ b/hw/ppc/spapr.c

@@ -1424,7 +1424,10 @@ static void ppc_spapr_reset(void)

     /* Check for unknown sysbus devices */

     foreach_dynamic_sysbus_device(find_unknown_sysbus_device, NULL);

-    if (kvm_enabled() && kvmppc_has_cap_mmu_radix()) {

+    first_ppc_cpu = POWERPC_CPU(first_cpu);

+    if (kvm_enabled() && kvmppc_has_cap_mmu_radix() &&

+        ppc_check_compat(first_ppc_cpu, CPU_POWERPC_LOGICAL_3_00, 0,

+                         spapr->max_compat_pvr)) {

         /* If using KVM with radix mode available, VCPUs can be started

          * without a HPT because KVM will start them in radix mode.

          * Set the GR bit in PATB so that we know there is no HPT. */

@@ -1483,7 +1486,6 @@ static void ppc_spapr_reset(void)

     g_free(fdt);

     /* Set up the entry state */

-    first_ppc_cpu = POWERPC_CPU(first_cpu);

     first_ppc_cpu->env.gpr[3] = fdt_addr;

     first_ppc_cpu->env.gpr[5] = 0;

     first_cpu->halted = 0;

-- 

1.8.3.1