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Re: [Qemu-devel] [RFC PATCH v2 6/6] hw: arm_gic_kvm: Add KVM VGIC save/r


From: Peter Maydell
Subject: Re: [Qemu-devel] [RFC PATCH v2 6/6] hw: arm_gic_kvm: Add KVM VGIC save/restore logic
Date: Tue, 15 Oct 2013 11:35:46 +0100

On 27 September 2013 09:11, Alex Bennée <address@hidden> wrote:
>
> address@hidden writes:
>
>> Save and restore the ARM KVM VGIC state from the kernel.  We rely on
> <snip>
>>
>>  static const VMStateDescription vmstate_gic = {
>>      .name = "arm_gic",
>> -    .version_id = 6,
>> -    .minimum_version_id = 6,
>> +    .version_id = 7,
>> +    .minimum_version_id = 7,
>>      .pre_save = gic_pre_save,
>>      .post_load = gic_post_load,
>>      .fields = (VMStateField[]) {
>
> Does this mean QEMU and Kernel need to be kept in lock-step for
> compatibility?

No. This patch is a little confusing because it's both adding
the new fields and also adding the save/restore support, but
once we have the data structures and vmstate in QEMU holding
all the state the kernel needs, there shouldn't be any need
to update the vmstate in a backwards-incompatible way.

>>
>> +//#define DEBUG_GIC_KVM
>> +
>> +#ifdef DEBUG_GIC_KVM
>> +static const int debug_gic_kvm = 1;
>> +#else
>> +static const int debug_gic_kvm = 0;
>> +#endif
>> +
>> +#define DPRINTF(fmt, ...) do { \
>> +        if (debug_gic_kvm) { \
>> +            printf("arm_gic: " fmt , ## __VA_ARGS__); \
>> +        } \
>> +    } while (0)
>> +
>
> Shouldn't we be using QEMU logging framework for this? Also for the
> fprintfs later on.

No, these are debug printfs, not things which would be interesting
to the average user/person trying to debug a guest. We don't
have a particularly clean framework for compile time
enabled debug printfs, so 'some random macro in each individual
file' is the current approach.

-- PMM



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