From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH RFC 2/3] xen/hvm: introduce a
 fpu_initialised filed to the CPU save record
Date: Wed, 14 Oct 2015 17:51:20 +0100
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To: Roger Pau Monne <roger.pau@citrix.com>, xen-devel@lists.xenproject.org
Cc: Jan Beulich <jbeulich@suse.com>
List-Id: xen-devel@lists.xenproject.org

On 14/10/15 17:24, Roger Pau Monne wrote:
> Introduce a new filed to signal if the FPU has been initialised or not. Xen

"field", I am guessing?

> diff --git a/xen/include/public/arch-x86/hvm/save.h b/xen/include/public/arch-x86/hvm/save.h
> index c7560f2..c4863be 100644
> --- a/xen/include/public/arch-x86/hvm/save.h
> +++ b/xen/include/public/arch-x86/hvm/save.h
> @@ -47,7 +47,8 @@ DECLARE_HVM_SAVE_TYPE(HEADER, 1, struct hvm_save_header);
>  /*
>   * Processor
>   *
> - * Compat: Pre-3.4 didn't have msr_tsc_aux
> + * Compat2: Pre-4.7 didn't have fpu_initialised
> + * Compat1: Pre-3.4 didn't have msr_tsc_aux

I would suggest reversing the Compat1 and 2 lines, to match chronology.

>   */
>  
>  struct hvm_hw_cpu {
> @@ -157,9 +158,121 @@ struct hvm_hw_cpu {
>      };
>      /* error code for pending event */
>      uint32_t error_code;
> +    /* is fpu initialised? */
> +    uint8_t fpu_initialised:1;

Bitfields can't be used in the public ABI, and please don't leave
trailing implicit padding.

I would recommend uint32_t flags and specify that bit 0 indicates that
fpu context is initialised.

~Andrew