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Re: [Qemu-devel] [PATCH 1/3] s390/migration: Provide a cpu save for init


From: Alexander Graf
Subject: Re: [Qemu-devel] [PATCH 1/3] s390/migration: Provide a cpu save for initial life migration work
Date: Wed, 21 Nov 2012 16:06:58 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.3) Gecko/20120306 Thunderbird/10.0.3

On 11/21/2012 04:03 PM, Christian Borntraeger wrote:
On 21/11/12 16:02, Alexander Graf wrote:
On 11/21/2012 03:59 PM, Christian Borntraeger wrote:
On 21/11/12 15:56, Alexander Graf wrote:
On 11/21/2012 03:46 PM, Christian Borntraeger wrote:
This provides a simple cpu load and save function. With the recent
addition of sync regs we have the crs,acrs, the prefix and the
PSW already up to date. Lets also save the fpu via pre/post hooks.

This patch also changes the license of machine.c to GPLv2 or later.
(The old code was just empty glue code, so there is no need
to go the "contributions after" way).

Signed-off-by: Christian Borntraeger<address@hidden>
---
    target-s390x/cpu.h     |    1 +
    target-s390x/machine.c |  115 
++++++++++++++++++++++++++++++++++++++++++------
    2 files changed, 103 insertions(+), 13 deletions(-)

diff --git a/target-s390x/cpu.h b/target-s390x/cpu.h
index 0f9a1f7..ba695dd 100644
--- a/target-s390x/cpu.h
+++ b/target-s390x/cpu.h
@@ -27,6 +27,7 @@
    #define ELF_MACHINE    EM_S390

    #define CPUArchState struct CPUS390XState
+#define CPU_SAVE_VERSION 1

    #include "cpu-defs.h"
    #define TARGET_PAGE_BITS 12
diff --git a/target-s390x/machine.c b/target-s390x/machine.c
index 3e79be6..02706fd 100644
--- a/target-s390x/machine.c
+++ b/target-s390x/machine.c
@@ -2,29 +2,118 @@
     * QEMU S390x machine definitions
     *
     * Copyright (c) 2009 Alexander Graf<address@hidden>
+ * Copyright IBM Corp. 2012
     *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; either
- * version 2 of the License, or (at your option) any later version.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, see<http://www.gnu.org/licenses/>.
+ * This work is licensed under the terms of the GNU GPL, version 2 or (at your
+ * option) any later version.  See the COPYING file in the top-level directory.
     */

    #include "hw/hw.h"
    #include "hw/boards.h"
+#include "cpu.h"
+#include "kvm.h"
+
+#if defined CONFIG_KVM
+static void cpu_pre_save(void *opaque)
+{
+    CPUS390XState *env = opaque;
+    struct kvm_fpu fpu;
+    int i, r;
+
+    if (!kvm_enabled()) {
+        return;
+    }
+
+    r = kvm_vcpu_ioctl(env, KVM_GET_FPU,&fpu);
+    assert(r == 0);
+    for (i = 0; i<    16; i++) {
+        env->fregs[i].ll = fpu.fprs[i];
+    }
+    env->fpc = fpu.fpc;
+}
+
+static int cpu_post_load(void *opaque, int version_id)
+{
+    CPUS390XState *env = opaque;
+    struct kvm_fpu fpu;
+    int i, r;
+
+    if (!kvm_enabled()) {
+        return 0;
+    }
+
+    for (i = 0; i<    16; i++) {
+        fpu.fprs[i] = env->fregs[i].ll;
+    }
+    fpu.fpc = env->fpc;
+
+    r = kvm_vcpu_ioctl(env, KVM_SET_FPU,&fpu);
+    assert(r == 0);
+
+    return 0;
+}
The kvm register sync needs to happen in the kvm register sync function :)
That would eliminate the whole purpose of sync regs and forces us to have an
expensive ioctl on lots of exits (again). I would prefer to sync the registers
that we never need in qemu just here.
That's why the register sync has different stages.
Not the get_register. Which is called on every synchronize_state. Which happen 
quite often
on s390.

Sounds like bad design then :).

Maybe we should explicitly tell the register synchronization which register sets to sync, so that we don't waste time getting _all_ the state every time we sync registers?

Jan, ideas?


Alex




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