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kvm: update eax documentation in signature cpuid

PATCH In review Michael S. Tsirkin 2 participants 2 messages May 1, 2012

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Michael S. Tsirkin

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#0 lore raw

PATCH 1/1 kvm: update eax documentation in signature cpuid

---

Pls apply on top of kvm cpuid bit.

Documentation/virtual/kvm/cpuid.txt +5 -1
index 8820685..c6e85d8 100644
@@ -10,11 +10,15 @@ a guest.
 KVM cpuid functions are:
 
 function: KVM_CPUID_SIGNATURE (0x40000000)
-returns : eax = 0,
+returns : eax = 0x40000001,
           ebx = 0x4b4d564b,
           ecx = 0x564b4d56,
           edx = 0x4d.
 Note that this value in ebx, ecx and edx corresponds to the string "KVMKVMKVM".
+The value in eax corresponds to the maximim cpuid function present in this leaf,
+and will be updated if more functions are added in the future.
+Note also that old hosts set eax value to 0x0. This should
+be interpreted as if the value was 0x40000001.
 This function queries the presence of KVM cpuid leafs.
#1 lore raw
Quoted 2 lines · On Tue, 1 May 2012 16:06:11 +0300 "Michael S. Tsirkin" <[email protected]> wrote:

Note that this value in ebx, ecx and edx corresponds to the string "KVMKVMKVM".
+The value in eax corresponds to the maximim cpuid function present in this leaf,

maximum?

Takuya

Quoted 4 lines
Documentation/virtual/kvm/cpuid.txt +3 -0
+and will be updated if more functions are added in the future.
+Note also that old hosts set eax value to 0x0. This should
+be interpreted as if the value was 0x40000001.
 This function queries the presence of KVM cpuid leafs.