linux-kernel - Re: [PATCH 2/4] KVM: Avoid checking huge page mappings in get_dirty

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 14 Mar 2012 07:58:13 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
Cc:	avi@...hat.com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] KVM: Avoid checking huge page mappings in
 get_dirty_log()

On Wed, Mar 14, 2012 at 02:34:32PM +0900, Takuya Yoshikawa wrote:
> Marcelo Tosatti <mtosatti@...hat.com> wrote:
> 
> > guest fault                                     enable dirty logging
> > 
> > tdp_page_fault (all _page_fault functions)      kvm_set_memory_region
> > 
> > 
> > level = mapping_level(vcpu, gfn)
> > (finds level == 2 or 3)
> > 
> > 
> >                                                 rcu_assign_pointer(slot
> > 								   with 
> >                                                                    ->dirty_bitmap)
> >                                                 synchronize_srcu_expedited()
> 
> Isn't here still in the SRCU read-side critical section?
> 
> > schedule()
> >                                                 kvm_arch_commit_memory_region()
> >                                                 spin_lock(mmu_lock)
> >                                                 kvm_mmu_slot_remove_write_access()
> > 						removes large sptes
> >                                                 spin_unlock(mmu_lock)
> > spin_lock(mmu_lock)
> > create large spte accordingly
> > to level above
> > spin_unlock(mmu_lock)
> > 
> 
> If so, we cannot start kvm_arch_commit_memory_region() until the completion
> of the SRCU critical section and this race will not happen.
> 
> 	Takuya

Correct.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/