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author | Keir Fraser <keir.fraser@citrix.com> | 2009-12-14 07:59:40 +0000 |
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committer | Keir Fraser <keir.fraser@citrix.com> | 2009-12-14 07:59:40 +0000 |
commit | ec35d23a92530b527e30788d85d99a161f226974 (patch) | |
tree | 8a9cd13612ec9f08711fb384a6c4f1cb977180e0 /docs | |
parent | a4a7c638f78e50b0e90dffef5792fde591d5712f (diff) | |
download | xen-ec35d23a92530b527e30788d85d99a161f226974.tar.gz xen-ec35d23a92530b527e30788d85d99a161f226974.tar.bz2 xen-ec35d23a92530b527e30788d85d99a161f226974.zip |
docs: add a document about guest cpuid configuration
Signed-off-by: Dexuan Cui <dexuan.cui@intel.com>
Diffstat (limited to 'docs')
-rw-r--r-- | docs/misc/cpuid-config-for-guest.txt | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/docs/misc/cpuid-config-for-guest.txt b/docs/misc/cpuid-config-for-guest.txt new file mode 100644 index 0000000000..1614dfed7e --- /dev/null +++ b/docs/misc/cpuid-config-for-guest.txt @@ -0,0 +1,23 @@ +CPUID emulation for guest +------------------------- + +When HVM guest tries to execute CPUID, or PV guest tries to execute XEN_CPUID, +the xen hypervior traps and emultes them. + +For HVM guest and PV DomU guest, xen's CPUID emulation can be adjusted using +the guest configation file if necessary (e.g., to supply better support for +guest live migration). The CPUID syntax in guest configration file is +described in detail in the examples like /etc/xen/xmexample.hvm, +/etc/xen/xmexample.hvm-stubdom. + +However, a user (or an administrator) must be aware that the CPUID in guest +configuration file can NOT be configured casually. The default CPUID +configuration should be safe, but illegal configuration can cause unexpected +behaviors of guest -- even can crash guest. + +For example, we should not expose the MONITOR CPUID feature flag (ECX bit 3; +CPUID executed EAX = 1) to HVM guest, otherwise, on guest's attempt of +executing MWAIT, the VMExit handler in Xen would inject #UD (Invalid Opcode +Exception) into the HVM guest, and guest kernel would panic. + +/* We can add more unsafe CPUID configuration here in future. */ |