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From: Fonyuy-Asheri Caleb <fonyuy-asheri.caleb@inria.fr>
To: xen-devel@lists.xenproject.org
Subject: file xen/include/xen/lib/x86/cpu-policy.h: Meaning of CPUID constants
Date: Mon, 6 May 2024 09:46:58 +0200 (CEST)	[thread overview]
Message-ID: <2066842119.4829764.1714981618946.JavaMail.zimbra@inria.fr> (raw)

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Hi, 
I am currently doing a study on the way xen handles CPUID information. 

I came across these constants in the code (xen/include/xen/lib/x86/cpu-policy.h file) but no explanation of why they have been set that way. 

#define CPUID_GUEST_NR_BASIC (0xdu + 1) 
#define CPUID_GUEST_NR_CACHE (5u + 1) 
#define CPUID_GUEST_NR_FEAT (2u + 1) 
#define CPUID_GUEST_NR_TOPO (1u + 1) 
#define CPUID_GUEST_NR_XSTATE (62u + 1) 
#define CPUID_GUEST_NR_EXTD_INTEL (0x8u + 1) 
#define CPUID_GUEST_NR_EXTD_AMD (0x21u + 1) 

Please can someone explain to me why we have these constants or point to a documentation which explains it? 
I am particularly interested in the CPUID_GUEST_NR_BASIC given that for intel processors for example, we have 
basic leaves running up to 0x21u already for recent processors. This value sort of forces a particular max leaf value. 


Caleb 

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             reply	other threads:[~2024-05-06  7:47 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-05-06  7:46 Fonyuy-Asheri Caleb [this message]
2024-05-06  8:13 ` file xen/include/xen/lib/x86/cpu-policy.h: Meaning of CPUID constants Jan Beulich
2024-05-06  8:34 ` Roger Pau Monné
2024-05-06  8:45   ` Fonyuy-Asheri Caleb
2024-05-06  8:47     ` Jan Beulich

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