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[Xen-devel] [PATCH 0/3] XSA-60 security hole fix

Recently Oracle developers found a Xen security issue as DOS affecting, named 
as XSA-60. Please refer http://xenbits.xen.org/xsa/advisory-60.html. Basically 
it involves how to handle guest cr0.cd setting, which under some environment it 
consumes much time resulting in DOS-like behavior.

These 3 patches is to fix XSA-60 security hole.

Patch 1/3 is a preparing patch for fixing XSA-60. Later patch will fix XSA-60 
via PAT under Intel EPT case, which depends on cpu_has_vmx_pat;

Patch 2/3 is to remove vmx_set_uc_mode logic, which result in XSA-60. It will 
be replaced by PAT approach at patch 3;

Patch 3/3 solves XSA-60 security hole:
1. For guest w/o VT-d, and for guest with VT-d but snooped, Xen need do 
nothing, since hardware snoop mechanism has ensured cache coherency;
2. For guest with VT-d but non-snooped, cache coherency can not be guaranteed 
by h/w snoop, therefore it need emulate UC type to guest:
    2.1). if it works w/ Intel EPT, set guest IA32_PAT fields as UC so that 
guest memory type are all UC;
    2.2). if it works w/ shadow, drop all shadows so that any new ones would be 
created on demand w/ UC;

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