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Re: [XEN PATCH] x86/hvm: Use constants for x86 modes
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Teddy Astie <teddy.astie@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 31 Oct 2024 15:17:59 +0100
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Paul Durrant <paul@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Thu, 31 Oct 2024 14:18:05 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 31.10.2024 15:13, Andrew Cooper wrote:
> On 31/10/2024 1:27 pm, Teddy Astie wrote:
>> In many places of x86 HVM code, constants integer are used to indicate in
>> what mode is
>> running the CPU (real, v86, 16-bits, 32-bits, 64-bits). However, these
>> constants are
>> are written directly as integer which hides the actual meaning of these
>> modes.
>>
>> This patch introduces X86_MODE_* macros and replace those occurences with it.
>>
>> Signed-off-by Teddy Astie <teddy.astie@xxxxxxxxxx>
>> ---
>> I am not sure of other places that uses these integer constants.
>
> I think you've got most of them.
>
> The problem (and it's preexisting, not something with your change), is
> that these aren't actually modes. They're all a combination of certain
> aspects of various modes settings.
>
> https://sandpile.org/x86/mode.htm has a pretty complete breakdown of modes.
>
> The problem is that here, we mostly want a shorthand for "code segment
> size", but including some aspects of how segmentation works.
Hence how about
#define X86_CODE_REAL 0
#define X86_CODE_VM86 1
#define X86_CODE_16BIT 2
#define X86_CODE_32BIT 4
#define X86_CODE_64BIT 8
?
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