KVM: MMU: fix race between 'walk_addr' and 'fetch'
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From: Avi Kivity on 11 Jul 2010 09:00 On 07/06/2010 01:45 PM, Xiao Guangrong wrote: > 'walk_addr' is out of mmu_lock's protection, so while we handle 'fetch', > then guest's mapping has modifited by other vcpu's write path, such as > invlpg, pte_write and other fetch path > > Fixed by checking all level's mapping > > > @@ -319,22 +319,23 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, > direct_access&= ~ACC_WRITE_MASK; > > for_each_shadow_entry(vcpu, addr, iterator) { > + bool nonpresent = false, last_mapping = false; > + > I don't like these two new variables, but no suggestion at the moment. I'll try to simplify this loop later. One idea may be: while (level > walker.level) { handle indirect pages } while (level > hlevel) { handle direct pages } handle last spte I'm worried that this change is too big for backporting, but no suggestions on how to make it smaller, so we'll have to accept it. > - spte = __pa(sp->spt) > - | PT_PRESENT_MASK | PT_ACCESSED_MASK > - | PT_WRITABLE_MASK | PT_USER_MASK; > - *sptep = spte; > + if (nonpresent) { > + spte = __pa(sp->spt) > + | PT_PRESENT_MASK | PT_ACCESSED_MASK > + | PT_WRITABLE_MASK | PT_USER_MASK; > + *sptep = spte; > + continue; > + } > Should be __set_spte(), but this already exists, so can be in a later patch. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Avi Kivity on 11 Jul 2010 11:50
On 07/11/2010 03:52 PM, Avi Kivity wrote: > On 07/06/2010 01:45 PM, Xiao Guangrong wrote: >> 'walk_addr' is out of mmu_lock's protection, so while we handle 'fetch', >> then guest's mapping has modifited by other vcpu's write path, such as >> invlpg, pte_write and other fetch path >> >> Fixed by checking all level's mapping >> >> >> @@ -319,22 +319,23 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, >> gva_t addr, >> direct_access&= ~ACC_WRITE_MASK; >> >> for_each_shadow_entry(vcpu, addr, iterator) { >> + bool nonpresent = false, last_mapping = false; >> + > > I don't like these two new variables, but no suggestion at the > moment. I'll try to simplify this loop later. > > One idea may be: > > while (level > walker.level) { > handle indirect pages > } > while (level > hlevel) { > handle direct pages > } > handle last spte > > I'm worried that this change is too big for backporting, but no > suggestions on how to make it smaller, so we'll have to accept it. Okay, I couldn't resist, posting this soon. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |