> -----Original Message----- > From: Avi Kivity [mailto:avi@xxxxxxxxxx] > Sent: Monday, May 21, 2012 4:32 PM > To: Hao, Xudong > Cc: Marcelo Tosatti; Xudong Hao; kvm@xxxxxxxxxxxxxxx; > linux-kernel@xxxxxxxxxxxxxxx; Shan, Haitao; Zhang, Xiantao > Subject: Re: [PATCH 4/4] Enabling Access bit when doing memory swapping > > On 05/21/2012 06:22 AM, Hao, Xudong wrote: > > > -----Original Message----- > > > From: Marcelo Tosatti [mailto:mtosatti@xxxxxxxxxx] > > > Sent: Friday, May 18, 2012 10:23 AM > > > To: Xudong Hao > > > Cc: avi@xxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > > > Shan, Haitao; Zhang, Xiantao; Hao, Xudong > > > Subject: Re: [PATCH 4/4] Enabling Access bit when doing memory swapping > > > > > > On Wed, May 16, 2012 at 09:12:30AM +0800, Xudong Hao wrote: > > > > Enabling Access bit when doing memory swapping. > > > > > > > > Signed-off-by: Haitao Shan <haitao.shan@xxxxxxxxx> > > > > Signed-off-by: Xudong Hao <xudong.hao@xxxxxxxxx> > > > > --- > > > > arch/x86/kvm/mmu.c | 13 +++++++------ > > > > arch/x86/kvm/vmx.c | 6 ++++-- > > > > 2 files changed, 11 insertions(+), 8 deletions(-) > > > > > > > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > > > > index ff053ca..5f55f98 100644 > > > > --- a/arch/x86/kvm/mmu.c > > > > +++ b/arch/x86/kvm/mmu.c > > > > @@ -1166,7 +1166,8 @@ static int kvm_age_rmapp(struct kvm *kvm, > > > unsigned long *rmapp, > > > > int young = 0; > > > > > > > > /* > > > > - * Emulate the accessed bit for EPT, by checking if this page has > > > > + * In case of absence of EPT Access and Dirty Bits supports, > > > > + * emulate the accessed bit for EPT, by checking if this page has > > > > * an EPT mapping, and clearing it if it does. On the next access, > > > > * a new EPT mapping will be established. > > > > * This has some overhead, but not as much as the cost of swapping > > > > @@ -1179,11 +1180,11 @@ static int kvm_age_rmapp(struct kvm *kvm, > > > unsigned long *rmapp, > > > > while (spte) { > > > > int _young; > > > > u64 _spte = *spte; > > > > - BUG_ON(!(_spte & PT_PRESENT_MASK)); > > > > - _young = _spte & PT_ACCESSED_MASK; > > > > + BUG_ON(!is_shadow_present_pte(_spte)); > > > > + _young = _spte & shadow_accessed_mask; > > > > if (_young) { > > > > young = 1; > > > > - clear_bit(PT_ACCESSED_SHIFT, (unsigned long *)spte); > > > > + *spte &= ~shadow_accessed_mask; > > > > } > > > > > > Now a dirty bit can be lost. Is there a reason to remove the clear_bit? > > > > The clear_bit() is called in shadown and EPT A/D mode, because > PT_ACCESSED_SHIFT does not make sense for EPT A/D bit, so use the code > shadow_accessed_mask to mask the bit for both of them. > > That doesn't answer the question. An atomic operation is now non-atomic. > > You can calculate shadow_accessed_bit and keep on using clear_bit(), or > switch to cmpxchg64(), but don't just drop the dirty bit here. > I know your meaning. How about this changes: ... young = 1; + if (enable_ept_ad_bits) + clear_bit(ffs(shadow_accessed_mask), (unsigned long *)spte); clear_bit(PT_ACCESSED_SHIFT, (unsigned long *)spte); ... > -- > error compiling committee.c: too many arguments to function -- 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
