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Re: [Qemu-ppc] [Qemu-devel] Unable to loadvm on qemu-system-ppc -M g3bei

From: Alexander Graf
Subject: Re: [Qemu-ppc] [Qemu-devel] Unable to loadvm on qemu-system-ppc -M g3beige (keyboard freeze)
Date: Fri, 19 Dec 2014 18:16:46 +0100
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.3.0

On 19.12.14 17:51, Mark Cave-Ayland wrote:
> On 19/12/14 16:35, Peter Maydell wrote:
>> On 19 December 2014 at 16:15, Mark Cave-Ayland
>> <address@hidden> wrote:
>>> It looks like after restoring the CPU state with loadvm env->htab_base
>>> is still at 0x0 rather than its pre-migration value of 0x7e000000.
>> Odd -- there is code that is at least trying to do that:
>> machine.c calls ppc_store_sdr1() which should set htab_base/mask
>> according to the migrated value of the register...
> Stepping through ppc_store_sdr1() I see the problem is the if() statement:
> if (env->spr[SPR_SDR1] != value) {
>    ....
> }
> It looks like env->spr[SPR_SDR1] has already been set to 0x7e000000
> before the call to ppc_store_sdr1() and so as the values are already
> equal then the code to setup env->htab_mask and env->htab_base is bypassed.
> The quick fix is to comment out the above if() statement which allows me
> to restore my OpenBIOS image successfully with -loadvm but sadly not my
> OS image (I guess there are probably a few more state bugs still lying
> around). Does this seem the right thing to do or is there a better way?

How about something like this instead? Then we at least don't lose the
acceleration we get from not invalidating the TLB on identical SDR1 writes.


diff --git a/target-ppc/machine.c b/target-ppc/machine.c
index c801b82..6f347bf 100644
--- a/target-ppc/machine.c
+++ b/target-ppc/machine.c
@@ -71,6 +71,7 @@ static int cpu_load_old(QEMUFile *f, void *opaque, int
     for (i = 0; i < 1024; i++)
         qemu_get_betls(f, &env->spr[i]);
     if (!env->external_htab) {
+        env->spr[SPR_SDR1] = 0;
         ppc_store_sdr1(env, sdr1);
     qemu_get_be32s(f, &env->vscr);

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