Re: [RFC v3 1/6] xen/arm: Add basic save/restore support for ARM

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 14/05/14 11:25, Ian Campbell wrote:
> On Thu, 2014-05-08 at 23:11 +0100, Andrew Cooper wrote:
>>> diff --git a/xen/include/public/arch-arm/hvm/save.h b/xen/include/public/arch-arm/hvm/save.h
>>> index 75b8e65..8312e7b 100644
>>> --- a/xen/include/public/arch-arm/hvm/save.h
>>> +++ b/xen/include/public/arch-arm/hvm/save.h
>>> @@ -3,6 +3,7 @@
>>>   * be saved along with the domain's memory and device-model state.
>>>   *
>>>   * Copyright (c) 2012 Citrix Systems Ltd.
>>> + * Copyright (c) 2014 Samsung Electronics.
>>>   *
>>>   * Permission is hereby granted, free of charge, to any person obtaining a copy
>>>   * of this software and associated documentation files (the "Software"), to
>>> @@ -26,6 +27,24 @@
>>>  #ifndef __XEN_PUBLIC_HVM_SAVE_ARM_H__
>>>  #define __XEN_PUBLIC_HVM_SAVE_ARM_H__
>>>  
>>> +#define HVM_ARM_FILE_MAGIC   0x92385520
>>> +#define HVM_ARM_FILE_VERSION 0x00000001
>>> +
>>> +/* Note: For compilation purpose hvm_save_header name is the same as x86,
>>> + * but layout is different. */
>>> +struct hvm_save_header
>>> +{
>>> +    uint32_t magic;             /* Must be HVM_ARM_FILE_MAGIC */
>>> +    uint32_t version;           /* File format version */
>>> +    uint32_t cpuinfo;           /* Record MIDR_EL1 info of saving machine */
>>> +};
>>> +DECLARE_HVM_SAVE_TYPE(HEADER, 1, struct hvm_save_header);
>>> +
>>> +/*
>>> + * Largest type-code in use
>>> + */
>>> +#define HVM_SAVE_CODE_MAX 1
>>> +
>>>  #endif
>>>  
>>>  /*
>> Hmm - it is quite poor to have this magically named "hvm_save_header".
> We frequently have arch interfaces where generic code requires arch code
> to provide particular structs or functions etc. What is poor about this
> particular instance of that pattern?
>
> Ian.
>

Save/restore is currently asymmetric in this regard.  The save side
treats this x86 structure as common, whereas load is entirely arch specific.

Fixing the asymmetry sensibly involves pushing the save side into arch code.

~Andrew