On 05/27/2011 05:56 AM, Tian, Kevin wrote:
> From: Yang, Wei Y > Sent: Thursday, May 26, 2011 9:29 PM > > This patchset enables a new CPU feature SMEP (Supervisor Mode Execution > Protection) in KVM. SMEP prevents kernel from executing code in application. > Updated Intel SDM describes this CPU feature. The document will be published > soon. > > This patchset is based on Fenghua's SMEP patch series, as referred by: > https://lkml.org/lkml/2011/5/17/523 > > Changes since v2: enable SMEP for spt mode. another change in this version is to avoid adding SMEP to cr4_guest_owned_bits, because architecturally it's required to flush TLB when CR4.SMEP is changed which has to be emulated.
That is actually a good change since it allows us to query SMEP without a vmcs_readl(GUEST_CR4).
Also based on your comment SMEP is now permitted based on cpuid setting. One pending issue though is check_cr_write in emulation path. We changed cr4_reserved_bits to vcpu specific instead of global, but check_cr_write doesn't provide a vcpu parameter. Looks the whole emulation logic avoids using vcpu context to be neutral. Avi, do you have any suggestion for a clean change here? Add cr_reserved_bits array into emulation context instead of hard-coding?
We can have a ->cpuid() callback so we can query it dynamically. cr4 writes will be emulated very rarely, after all.
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