Re: [Qemu-devel] [PATCH] i440fx: implement reset

[Andreas Färber]

Am 20.02.2013 17:17, schrieb Andreas Färber:
> Am 20.02.2013 16:35, schrieb David Woodhouse:
>> This implements reset functionality for the i440FX, resetting all the
>> PAM registers to their power-on defaults of no RAM access and thus
>> forwarding all access to the 0xc0000-0xfffff range to PCI address space
>> (i.e. to the actual ROM) instead of RAM.
>>
>> Fixing this is sufficient to work around a KVM bug which causes it to
>> run 16-bit code at 0xffff0 instead of 0xfffffff0 on CPU reset. If reset
>> was working correctly on the i440FX, that KVM bug wouldn't have
>> *mattered* because the two addresses would have identical contents.
>>
>> There's been much discussion about the distinction between hard reset
>> and soft reset, and the fact that many of our reset triggers (such as
>> the keyboard controller and triple-fault handler) are actually doing a
>> full system-wide hard reset when in fact they should be triggering
>> something much more limited in scope.
>>
>> This patch exacerbates that existing problem only slightly, by causing
>> the offending triggers to reset yet another piece of hardware that they
>> shouldn't have been resetting. But the problem is largely theoretical
>> anyway; mostly limited to 80286 protected mode software which needs to
>> initiate a CPU reset to get back into real mode, but which *doesn't*
>> want a full system reset. Such software is almost certainly already
>> broken under Qemu anyway, because of all the *other* aspects of a full
>> hard reset that are already happening.
>>
>> So this patch can be applied separately from any longer-term fixes to
>> make the 'soft' reset actually do the right thing.
>>
>> Signed-off-by: David Woodhouse <address@hidden>
>>
>> diff --git a/hw/piix_pci.c b/hw/piix_pci.c
>> index 6c77e49..f81c6aa 100644
>> --- a/hw/piix_pci.c
>> +++ b/hw/piix_pci.c
>> @@ -171,6 +171,24 @@ static int i440fx_load_old(QEMUFile* f, void *opaque, 
>> int version_id)
>>      return 0;
>>  }
>>  
>> +static void i440fx_reset(DeviceState *ds)
>> +{
>> +    PCIDevice *dev = DO_UPCAST(PCIDevice, qdev, ds);
>> +    PCII440FXState *d = DO_UPCAST(PCII440FXState, dev, dev);
> 
> Please don't use DO_UPCAST() on QOM objects, there's QOM cast macros for
> this, like PCI_DEVICE(). If there's one missing for PCII440FXState (I
> think I only added them for the PHB itself?), it's two lines to add.
> 
>> +    uint8_t *pci_conf = d->dev.config;

In the same spirit that should be dev->config, not d->dev.config BTW.

Cf. http://wiki.qemu.org/QOMConventions

Andreas

>> +
>> +    pci_conf[0x59] = 0x00; // Reset PAM setup
> 
> scripts/checkpatch.pl will complain about this comment style.
> 
>> +    pci_conf[0x5a] = 0x00;
>> +    pci_conf[0x5b] = 0x00;
>> +    pci_conf[0x5c] = 0x00;
>> +    pci_conf[0x5d] = 0x00;
>> +    pci_conf[0x5e] = 0x00;
>> +    pci_conf[0x5f] = 0x00;
>> +    pci_conf[0x72] = 0x02; // And SMM
>> +
>> +    i440fx_update_memory_mappings(d);
>> +}
>> +
>>  static int i440fx_post_load(void *opaque, int version_id)
>>  {
>>      PCII440FXState *d = opaque;
>> @@ -615,6 +633,7 @@ static void i440fx_class_init(ObjectClass *klass, void 
>> *data)
>>      dc->desc = "Host bridge";
>>      dc->no_user = 1;
>>      dc->vmsd = &vmstate_i440fx;
>> +    dc->reset = i440fx_reset;
>>  }
>>  
>>  static const TypeInfo i440fx_info = {
> 
> Otherwise looks okay.
> 
> Andreas

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