On 04/08/2015 15:10, Xiao Guangrong wrote: >> >> This should be cpu_has_nx, I think. > > cpu_has_nx() checks the feature on host CPU, however, this is the shadow > page table which completely follow guest's features. > > E.g, if guest does not execution-protect the physical page, then > KVM does not do it either. That's just true for current code. In principle you could add a memslot flag for KVM_MEMSLOT_NO_EXECUTE, then NX would be true on an spte but not on a PTE. >> >>> + guest_cpuid_has_gbpages(vcpu), >> >> This should be cpu_has_gbpages. > > E.g, if guest does not use 1G page size, it's also not used in shadow page > table. However, bit 7 in the shadow PDPTE is not reserved. If you're not testing "is this bit reserved" but rather "should this bit be always zero" in the SPTE, then checking guest_cpuid is okay. But in that case shadow_rsvd_check is really more like shadow_always_zero_check. >> >>> is_pse(vcpu)); >> >> This should be cpu_has_pse. > > E.g, guest does no use 4M page size, then KVM does not use it either. Right, it should always be true, not cpu_has_pse, because PAE and 64-bit page tables always support huge (2M) pages. Or as above, if you're testing "should this bit be always zero" then it's a different story. Paolo > BTW, cpu_pse only hurts 32 bit page table which is not used by shadow > page table (32 PAE and 64 Long mode are used in shadow page). > > Only tdp only follows host CPU's features, KVM does not use NX to > protect the page, so i always mark it as false in > reset_tdp_shadow_rsvds_bits_mask(). -- 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
