Re: [PATCH] support piix PAM registers in KVM

[Avi Kivity <avi@redhat.com>]

On 06/15/2011 02:58 PM, Jason Krieg wrote:
> On 09/21/2010 02:31 PM, Gleb Natapov wrote:
>> Without this BIOS fails to remap 0xf0000 memory from ROM to RAM so 
>> writes
>> to F-segment modify ROM content instead of memory copy. Since QEMU does
>> not reloads ROMs during reset on next boot modified copy of BIOS is 
>> used.
>>
>> Signed-off-by: Gleb Natapov<gleb@redhat.com>
>> diff --git a/hw/piix_pci.c b/hw/piix_pci.c
>> index 933ad86..0bf435d 100644
>> --- a/hw/piix_pci.c
>> +++ b/hw/piix_pci.c
>> @@ -99,10 +99,6 @@ static void 
>> i440fx_update_memory_mappings(PCII440FXState *d)
>>       int i, r;
>>       uint32_t smram, addr;
>>
>> -    if (kvm_enabled()) {
>> -        /* FIXME: Support remappings and protection changes. */
>> -        return;
>> -    }
>>       update_pam(d, 0xf0000, 0x100000, (d->dev.config[I440FX_PAM]>>  
>> 4)&  3);
>>       for(i = 0; i<  12; i++) {
>>           r = (d->dev.config[(i>>  1) + (I440FX_PAM + 1)]>>  ((i&  1) 
>> * 4))&  3;
>> -- 
>>             Gleb.
>> -- 
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>
> Hi,
>
> While testing migration from old to new kvm ( 0.12.5 to 0.14.x ) and 
> after fixing
> some other problems mainly version_id probs in some of the 
> VMStateDescriptions
> everything was working fine until I tried to migrate Windows guests 
> they would crash
> after running some time. Linux guests are running stable.
>
> So I decided to do a git bisect to identify the according commit.
> Reverting this commit fixes this problem with Windows guests.
>
> What consequences might it have not updating these memory mappings ?
>

Resets may fail.

> Does this commit need a specific seabios version, we have seabios 
> 0.6.0 with qemu-kvm 0.12.5
> and seabios 0.6.1.2 with qemu-kvm 0.14.1 ?

IIUC newer seabios depends on this commit, but this commit does not 
depend on seabios.

>
> Maybe instead of reverting this commit one could check the seabios 
> version in this method
> and only do an update of these piix PAM registers if running with a 
> newer seabios version ?

It would be better to first understand what's going wrong.

-- 
error compiling committee.c: too many arguments to function