On 04/22/2012 11:12 PM, Avi Kivity wrote: > On 04/21/2012 07:22 AM, Marcelo Tosatti wrote: >> On Sat, Apr 21, 2012 at 11:30:55AM +0800, Xiao Guangrong wrote: >>> On 04/21/2012 05:39 AM, Marcelo Tosatti wrote: >>> >>> >>>>> @@ -1177,9 +1178,8 @@ static int kvm_set_pte_rmapp(struct kvm *kvm, unsigned long *rmapp, >>>>> new_spte = *sptep & ~PT64_BASE_ADDR_MASK; >>>>> new_spte |= (u64)new_pfn << PAGE_SHIFT; >>>>> >>>>> - new_spte &= ~PT_WRITABLE_MASK; >>>>> - new_spte &= ~SPTE_HOST_WRITEABLE; >>>>> - new_spte &= ~shadow_accessed_mask; >>>>> + new_spte &= ~(PT_WRITABLE_MASK | SPTE_HOST_WRITEABLE | >>>>> + shadow_accessed_mask | SPTE_ALLOW_WRITE); >>>> >>>> Each bit should have a distinct meaning. Here the host pte is being >>>> write-protected, which means only the SPTE_HOST_WRITEABLE bit >>>> should be cleared. >>> >>> >>> Hmm, it is no problem if SPTE_ALLOW_WRITE is not cleared. >>> >>> But the meaning of SPTE_ALLOW_WRITE will become strange: we will see a >>> spte with spte.SPTE_ALLOW_WRITE = 1 (means the spte is writable on host >>> and guest) and spte.SPTE_HOST_WRITEABLE = 0 (means the spte is read-only >>> on host). >> >> You are combining gpte writable bit, and host pte writable bit (which >> are separate and independent of each other) into one bit. >> >> SPTE_HOST_WRITEABLE already indicates whether the host pte is writable >> or not. > > Maybe we should rename SPTE_ALLOW_WRITE to SPTE_NOT_SHADOWED (or > SPTE_SHADOWED with the opposite meaning). > > Alternatively, SPTE_MMU_WRITEABLE (complements SPTE_HOST_WRITEABLE). > I like SPTE_MMU_WRITEABLE :) -- 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
