Re: [PATCH v2] KVM: x86/MMU: Do not check unsync status for root SP.

[Paolo Bonzini]

On 08/02/21 14:49, Yu Zhang wrote:
> On Mon, Feb 08, 2021 at 12:36:57PM +0100, Paolo Bonzini wrote:
> > On 07/02/21 13:22, Yu Zhang wrote:
> > > In shadow page table, only leaf SPs may be marked as unsync.
> > > And for non-leaf SPs, we use unsync_children to keep the number
> > > of the unsynced children. In kvm_mmu_sync_root(), sp->unsync
> > > shall always be zero for the root SP, , hence no need to check
> > > it. Instead, a warning inside mmu_sync_children() is added, in
> > > case someone incorrectly used it.
> > >
> > > Also, clarify the mmu_need_write_protect(), by moving the warning
> > > into kvm_unsync_page().
> > >
> > > Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>
> > > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> >
> > This should really be more of a Co-developed-by, and there are a couple
> > adjustments that could be made in the commit message.  I've queued the patch
> > and I'll fix it up later.
>
> Indeed. Thanks for the remind, and I'll pay attention in the future. :)

Also:

arch/x86/kvm/mmu/mmu.c: In function ‘mmu_sync_children’:
arch/x86/kvm/mmu/mmu.c:2002:17: error: ‘sp’ is used uninitialized in 
this function [-Werror=uninitialized]
  WARN_ON_ONCE(sp->unsync);

so how was this tested?

Paolo