On 24/06/2016 06:50, Bandan Das wrote: >>> >> I am tempted to remove the FNAME version altogether and change >>> >> is_present_gpte() >>> >> to return (pte & PT_PRESENT_MASK) || (shadow_xonly_valid && (pte & 4)). This >>> >> will take care of all cases. Hope I am not missing something :) >> > >> > Please rename the non-FNAME version to pae_is_present_pdpte or just inline >> > it in the two callers. > I am still not sure why the FNAME version is needed, specifically the PTTYPE_EPT > specific check. Why can't we just check for execonly and the corresponding > bit in the non FNAME version ? The FNAME version encodes the right semantics: 1) for non-EPT page tables, bit 1 indicates present. 2) for EPT page tables, setting any bit 0-2 indicates present. It's perfectly fine to find that a PTE is invalid *after* judging that it is present. There is no difference between setting bit 51 on a PTE, and having the invalid -W- combination on an EPT page table entry. In both cases, the page is present but the PTE is invalid. The SDM is very clear about it: "If bits 2:0 of an EPT paging-structure entry are all 0, the entry is not present". So if bits 2:0 are -W- the entry is present but invalid, and causes an EPT misconfiguration vmexit. A non-present entry will cause an EPT violation instead. Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
