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

[Christian Borntraeger <borntraeger@de.ibm.com>]

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<borntraeger@de.ibm.com>
>> ---
>>   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<agraf@suse.de>
>> + * 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.